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Living at the Extremes: Extremophiles and the Limits of Life in a Planetary Context

Nancy Merino, Heidi S. Aronson, Diana P. Bojanova and 4 more

Frontiers in Microbiology · 2019 · Review · CC BY

Abstract

Prokaryotic life has dominated most of the evolutionary history of our planet, evolving to occupy virtually all available environmental niches. Extremophiles, especially those thriving under multiple extremes, represent a key area of research for multiple disciplines, spanning from the study of adaptations to harsh conditions, to the biogeochemical cycling of elements. Extremophile research also has implications for origin of life studies and the search for life on other planetary and celestial bodies. In this article, we will review the current state of knowledge for the biospace in which life operates on Earth and will discuss it in a planetary context, highlighting knowledge gaps and areas of opportunity.

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From PubMed Central, U.S. National Library of Medicine, as current on Oct 18, 2026. Paragraph numbers are ours, so an answer can point at one.

(Poly)Extremophiles Help Us Predict the Boundaries of Life

1Over the past century, the boundary conditions under which life can thrive have been pushed in every possible direction, encompassing broader swaths of temperature, pH, pressure, radiation, salinity, energy, and nutrient limitation. Microorganisms do not only thrive under such a broad spectrum of parameters on Earth, but can also survive the harsh conditions of space, an environment with extreme radiation, vacuum pressure, extremely variable temperature, and microgravity. The definition of “extreme conditions” has strong anthropocentric criteria, rather than microbial criteria, and can be the cause of confusion. When considering extremophilic (as opposed to extremotolerant) organisms, it is important to keep in mind that these are highly adapted organisms for the conditions considered and that the “extreme” condition constitutes the norm under which the organism is able to metabolically and biochemically operate. Moreover, there are myriad environments on our planet’s surface – and especially subsurface – that exhibit extremes in one or more physical or chemical condition. Therefore, extremophiles and, in particular, polyextremophiles might be the most abundant lifeforms on our planet. In addition, if we consider that the current planetary surface conditions on Earth (such as mean temperature, redox state, and oxygenic atmosphere) have only occurred for a short period of time compared to the existence of life, we might conclude that the extremophilic way of life has actually dominated the evolutionary history of life on our planet.

2Over the past several decades, the isolation of culturable (poly)extremophiles and the identification of extreme microbial communities through various culture-independent approaches have provided key insights into the boundaries of life. Research on (poly)extremophiles has led to numerous advances in molecular biology and medicine, while simultaneously reshaping our understanding of the origins and evolution of life and the potential for life on other planetary bodies. Several reviews have defined extremophiles (Table 1) (e.g.,;;; ) and discussed the physiology and genetics of (poly)extremophiles in detail (e.g., chapters within Polyextremophiles: Life Under Multiple Forms of Stress, edited by ). To build upon these discussions, this paper will review the parameters that limit life, providing ranges under which life has been detected, herein defined as “boundary conditions.” We will then map the currently known boundary conditions of life on Earth to the possible conditions or theoretical space that life could occupy on Earth. Finally, we will explore the prospect of using this information for the search of life on other planetary bodies.

Parameters That Limit Life

3Our knowledge of life is based on the observable and measurable phenomena that occur on Earth, and is therefore limited to this instance of life. However, the laws of chemistry and physics have universal principles which enable us to extrapolate to the conditions under which life could survive elsewhere. These principles suggest that life requires a liquid solvent, an energy source, and building blocks.

4While the bulk abundance of (inorganic) building blocks appears not to be a factor limiting the distribution of life on Earth (with subsurface environments as a possible exception, e.g., ) and, potentially, other planetary bodies, the availability of a solvent is considered to be a key factor. While the potential for other liquid solvents to sustain extraterrestrial life is discussed in detail elsewhere ( and references therein), water is considered the most likely liquid solvent because of its cosmic abundance and physicochemical properties. Water, especially the availability of liquid water, appears to be the main factor controlling the dimensions of the biospace for life on Earth (i.e., the parameter space occupied by life). Liquid water acts both as a solvent and a reactant/product in biochemical reactions, and its numerous unique physicochemical properties have profoundly shaped the emergence and evolution of life on our planet. As discussed in this review below, water activity appears to be the single key parameter controlling the biospace of Earth’s life, and numerous other parameters limiting life (e.g., temperature and salinity) are, in fact, acting on the availability of water. At the ecosystem level, water can indirectly influence the variation of key physicochemical conditions, which in turn controls microbial community composition and diversity, profoundly influencing geobiochemical cycling (sensu ).

5Life also needs a source of energy to power chemical reactions, and redox chemistry appears to be universal. Physicochemical gradients create non-equilibrium redox conditions that have played an important role in the origins, evolution, and diversity of life. Redox and proton gradients were likely the two main mechanisms involved in the origins of life, initiating the necessary energy flux to drive metabolism and growth. Therefore, the current search for life’s limits has extended beyond temperature, pH, pressure, salinity, and radiation gradients (each parameter discussed in their respective sections) and also includes the possible energetic and nutrient limits of life (discussed in;; ).

6The parameters discussed herein (temperature, pH, pressure, salinity, and radiation) correlate with each other and can influence the availability of nutrients and energy sources. Depending on the environment, certain parameters can more strongly influence microbial diversity over others, such as temperature in geothermal waters, pH in soil communities, salinity in saline lakes, and water content in dry climates. On the nano- and micro-scale level, the two most important factors are likely water activity and pH, which influence the chemiosmotic, energy-generating gradient at the cell level. In contrast, parameters that influence the macro-scale level vary with the ecosystem. For example, temperature plays a significant role in geothermal environments and influences such processes as water-rock interactions and degassing. Water-rock interactions can then impact microorganisms by limiting the availability of trace elements and electron donors/acceptors.

7Microorganisms have been detected in a variety of extreme environments (Figure 1), virtually in any location where liquid water is available for life to use. This demonstrates that life can adapt to a wide range of parameters (Figure 2). It is therefore imperative to determine the minima and maxima for each parameter, and even more importantly, to understand their combined effects, in order to evaluate the limits of Earth’s life and advance our understanding of the potential for life elsewhere.

Acidity and Alkalinity

8Extremely low and high pH environments have been observed for different ecosystems on Earth (Table 2). Extreme pH values were observed for ecosystems contaminated by mining waste, with current extremes reported from Iron Mountain (Shasta County, CA, United States) (pH -3.6) and Gorka Lake (Chrzanow region, Poland) (pH 13.3; ). While there has yet to be any microbial community studies or isolation attempts for Gorka Lake, to the best of our knowledge, microbial communities have been explored at Iron Mountain, with several microorganisms isolated [e.g., Thermoplasmales, Acidithiobacillus ferrooxidans, and Leptospirillum ferrooxidans]. Despite this, there are currently no cultured or isolated microorganisms which can be grown at either of the listed extremes. Currently, the most extreme acidophile and alkaliphile can survive at pH 0 and pH 12.5, respectively (pHopt 0.7 and 11) (Table 3). The lowest pHmin -0.06 was observed for two hyperacidophilic Archaea known as Picrophilus oshimae and P. torridus (pHopt 0.7), isolated from a solfataric hot spring in Noboribetsu (Hokkaido, Japan). These heterotrophic and aerobic polyextremophiles can also withstand temperatures of up to 65°C (Topt = 60°C, Tmin = 47°C), potentially through increased cyclization of their tetraether membrane lipids as a generalized response to pH, temperature, and nutrient stress. Other thermoacidophiles also include those species within the genus Sulfolobus, in which several isolates are known to be genetically tractable. In comparison to extreme acidophily, the highest pHmax of 12.5 was observed for an alkaliphilic, aerobic, mesophilic bacterium known as Serpentinomonas sp. B1 (pHopt 11), isolated from a terrestrial serpentinizing system, The Cedars (CA, United States). Although there is a report of the highest pHmax 13 held by Plectonema nostocorum, this has not been further confirmed. The largest pH range, as compared to other isolated microorganisms, was observed for Halomonas campisalis (pHrange 6–12), a haloalkaliphilic bacterium isolated from a soda lake (Soap Lake, WA, United States) (Table 4).

9The pH has a significant effect on microorganisms and microbial consortia, ranging from the nano- to macro-scale level. All microorganisms must maintain a near neutral cytoplasmic pH to enable cellular functions for survival and metabolism. The cytoplasmic pH of acidophilic bacteria is ∼6.0 while alkaliphilic bacteria have a cytoplasmic pH around 7.2–8.7. For more information on the molecular mechanisms behind pH homeostasis, provide a detailed review. The homeostasis of protons (and other ions) through various transporters, including the ion-utilizing ATP synthase, was likely one of the first functions to develop within the earliest cells. Indeed, chemiosmosis is a property of both archaeal and bacterial cells. In addition to intracellular pH, microorganisms can excrete organic metabolites, such as lactic acid or acetic acid, thereby changing the immediate, surrounding pH. Many acidophiles also have organic acid degradation pathways to prevent proton uncoupling by organic acids. It has been demonstrated both in natural settings and laboratory cultures that microorganisms can significantly alter their environmental pH as a result of metabolic reactions. For example, sulfide, thiosulfate, and elemental sulfur oxidizers secrete sulfate and protons as by-products, significantly acidifying their environment. This ability is used industrially for the bio-leaching of sulfide ore deposit and it is largely responsible for the low pH of acid mine drainage fluids and other acidic environments. Recent work by suggests that thermoacidophilic archaea and the acidity of their habitats co-evolved after the evolution of oxygenic photosynthesis (since oxygen is used as primary electron acceptor in the metabolisms), showing a significant example of niche engineering and geosphere-biosphere coevolution. All together, these findings suggest that pH can be metabolically controlled either at the intracellular or local level, as compared to temperature, radiation, salinity, and pressure.

10On the macro-scale level, pH can dominate as the main parameter affecting microbial community composition and abundances. Several studies demonstrate that pH affects microbial community diversity more than any other parameter tested (e.g.,;;;; ). For example, distinct microbial communities were observed with changes in pH (pHrange 1.9–4.1), in which the genus Ferrovum dominated at higher pH while the phyla Alphaproteobacteria, Gammaproteobacteria, Nitrospirae, and Euryarchaeota were present at lower pHs. Similarly, bacterial community composition changed with increasing pH in alkaline sediments of a Tibetan plateau (pHrange 6.88–10.37). Changes in community composition are likely derived from the range in which microorganisms can survive. Most cultured microbes live within a narrow pH range of three to four units, although some exceptions occur [e.g., fungal isolates can grow over five to nine pH units]. Moreover, it has been suggested that archaeal and fungal communities may be less affected by changes in pH compared to bacteria.

Salinity and Water Activity

11Salinity has a significant impact on microbial community composition. Saline environments comprise a large portion of the Earth and range from the marine environment (∼3–4% salinity), hot springs (up to 10.5% salinity), and to soda lakes (up to 37.1% salinity), and even salt inclusions [up to 49.7% salinity] (Figure 2 and Table 2). Salinity can also vary significantly on smaller scales, for example, in tidal pools, or on salt mineral grains due to water deliquescence. A wide range of different ions, including Na++, Cl-, SO42-, Ca2+, and Mg2+ can contribute to total salinity in the environment. The ionic composition can significantly influence water activities, especially in the presence of high concentrations chaotropic salts, like in the athalassic deep-sea hypersaline anoxic basins of the Mediterranean Sea. In addition, water availability in terrestrial saline environments is further influenced by precipitation rates relative to evaporation, resulting in increasing concentration of salts.

12The salinity range and optimum for cultivable and isolated microorganisms is between 0 and 35%. The current highest salinity record holder is Halarsenatibacter silvermanii strain SLAS-1T, isolated from the alkaline hypersaline Searles Lake (CA, United States) (salinityopt 35% NaCl). Halophiles are found in all three domains of life. Current hyperhalophiles in culture include bacteria and archaea which can grow over a salinity of ∼15% NaCl. There are also polyextremophiles, for example, the bacterium Halomonas campisalis (Table 4), isolated from a soda lake (Soap Lake, WA, United States) is a moderate halophile and alkaliphile (salinityopt = 8.8%, pHopt = 9.5) and can tolerate extreme pH up to 12 and salinities up to 26.3%.

13Halophiles achieve the necessary osmotic balance by one of two strategies: (1) accumulating K+ in the cytoplasm as a ‘salt-in’ strategy or (2) excluding salts by synthesizing compatible organic solutes, such as polyols, amino acids, sugars, and betaines. The ‘salt-in’ strategy has been identified only in a few halophiles (e.g., Salinibacter and Halanaerobiales) which require KCl to have functional proteins. In contrast, many microorganisms that utilize the salt exclusion strategy can tolerate a wider range of salt concentrations due to the production of organic solutes to counter the concentration of salts. The necessary energy needed to maintain osmosis, and the thermodynamics of surviving under saline conditions have been thoroughly discussed by.

14Many microorganisms in saline environments must also adapt to low water activity (the mole fraction of water) and increased radiation (discussed in section “Radiation”). Although salts can lower the freezing point of water, saturated salt solutions have low water activity. Water activity is the only other parameter, aside from pH and salinity, that some microorganisms can regulate through the production of metabolites capable of storing or attracting water (e.g., proteins and polysaccharides from EPS). The theoretical water activity minima for halophilic archaea and bacteria is 0.611 aw while it is 0.632 aw for fungi. In comparison, the water activity of NaCl saturated solutions is estimated to be 0.755 aw while pure water is 1 aw.

15The theoretical water activity limit has been surpassed by microbial life. When there are high concentrations of the chaotropic MgCl2 or CaCl2, the water activity is lowered even more (e.g., 0.3 aw for a saturated MgCl2 solution). For example, environmental surveys reported microbial communities in the brines of two athalassic deep-sea hypersaline anoxic basin (DHAB), Discovery (MgCl2 ≥ 5 M, T = 14.5°C) and Kryos Basin (saturated MgCl2, ∼0.4 aw, T = 16.5°C), both located in the Mediterranean Sea. The Kryos Basin microbial community, located in the brine, consisted of active sulfate-reducers, with sulfate reduction reaching up to 460 μmol/kg-day. In contrast to the DHABs, microbial life has yet to be shown to exist in a CaCl2-dominated brine with up to 474 g/L total dissolved salts (Don Juan Pond, Antarctica). This is likely due to both extreme temperature and salinity conditions, as Don Juan Pond is an unfrozen lake (pH 4.6) with an average depth of 11 cm and temperatures reaching below -36°C (Tmax ∼ 20°C). The estimated water activity in Don Juan Pond is likely below 0.45 aw but could be between 0.28 aw (25°C) to 0.61 aw (–50°C), as estimated for a CaCl2-dominated brine with antarcticite (CaCl2⋅6H2O) precipitation.

Temperature

16The temperature on Earth’s surface ranges from -98.6 to 495°C [ultra-cold locations in East Antarctica and extremely hot deep-sea hydrothermal vents], with much higher temperatures possible in magma influenced subsurface environments (Table 2). Fluid temperatures above 100°C are possible whenever the combination of hydrothermal or magmatic activity is present together with high pressure, for example, in the deep subsurface near volcanoes or at deep-sea hydrothermal vents. In the absence of geothermal influence, the highest surface temperature reported on Earth is ∼71°C, in the Lut Desert (Iran). The current temperature extreme that microbial life can survive extends from -25°C (Tmin, Deinococcus geothermalis DSM 11300) to 130°C (Tmax, “Geogemma barossii” 121) (Table 4). Around -26°C to -10°C, microbial cells will likely become vitrified (without intracellular freezing), enabling cells to survive low temperatures. The temperature range in which microorganisms are reported to be metabolically active is currently between -20°C (an enrichment culture from the Siberian permafrost soil) and 122°C (Methanopyrus kandleri 116; ). In comparison, the lowest temperature in which a pure culture isolate is capable of growing is -15°C with 18% salinity (Planococcus halocryophilus Or1;, ).

17The upper temperature of life has been raised several times in the past 50 years of research, and current environmental and theoretical studies suggest that the upper limit of life might lay near ∼150°C, due primarily to the instability of macromolecules above this temperature. Similarly, thermodynamic considerations suggest that life might be impossible below -40°C, thus the current theoretical boundaries for life are -40°C to 150°C. It is still possible, however, that the boundary conditions of life might extend past these limits, and the surpassing of previous historical theoretical limits suggest that future studies might unveil unexpected adaptation strategies.

18Extreme temperature adaptations by psychrophiles and thermophiles generally involve either high saline or pressure conditions. High saline, cold environments enable the growth of halopsychrophiles. Liquid inclusions in sea ice are due to the high concentrations of salts, which lower the freezing point of water, and this liquid fraction can still be observed at -40°C (theoretical seawater eutectic temperature is -55°C). Microbial consortia are likely to inhabit subzero brine veins, especially those surrounding soil particles, where salts and organic materials (e.g., the microbially produced extracellular polymeric substances or EPS) are concentrated. Indeed, the majority of active bacteria and archaea observed in Arctic wintertime sea-ice cores at -20°C were all particle-associated. In contrast to halopsychrophiles, there are very few halothermophiles, with a combined temperature range of 17–70°C (Topt = 50–65°C) and salinity range 2.9–29.2% (salinityopt = 11.7–26.3% NaCl). Several hyperthermophiles (growth at >80°C) must grow at high pressure conditions because high pressure allows water to remain liquid at higher temperatures, with an upper theoretical limit of 407°C at 29.8 MPa pressure. Hyperthermopiezophilic microorganisms, such as Methanopyrus kandleri strain 116 and “Geogemma barossii” strain 121 (Table 4), are able to maintain cell structural integrity due to the contrasting effects of high temperature and high pressure.

19Macro-scale temperature gradients demonstrate the influence of temperature on microbial community composition within an ecosystem. In this regard, the effect of increasing temperature gradients, especially in geothermal-influenced environments, have been studied to greater extent compared to decreasing temperature gradients. In general, the community complexity decreases with increasing temperatures on the scale of centimeters to meters. For example, the soil microbial community of Tengchong Geothermal Field (China) shifted toward lower diversity with increasing temperatures (50–90.2°C and 32–36 MPa) and became dominated by Archaea. Similar patterns have been also reported for deep-sea and shallow-water hydrothermal vents. Temperature gradients likely have more influence on the microbial community of geothermal environments, as compared to other environments (e.g., soil), where pH and salinity have been shown to be the dominant factor (see sections “Acidity and Alkalinity” and “Salinity and Water Activity”).

Pressure

20As mentioned above, pressure influences microbial growth, especially under extreme temperatures. On Earth’s surface, pressure ranges from 0.1 to 112 MPa (Table 2), with higher pressures observed at subduction zones (e.g., 900 MPa at the top of a subducting plate, Mariana Forearc; ) and subsurface environments (e.g., ). It is estimated that microbial life could be supported at subduction zone forearcs with pressures ∼340 MPa. Several piezophiles and piezotolerant microorganisms have been isolated from deep-sea locations (Table 3), and the current record holder is Thermococcus piezophilus, a thermophilic Archaeon able to survive up to 125 MPa (Popt = 50 MPa, Pgrowth range = 0.1–125 MPa). Piezophiles have lower generation times at higher pressure than at atmospheric pressure, and considering the average depth of the ocean is 3,800 m (average pressure 38 MPa), with bottom temperatures between 0 and 3°C, there is likely a vast number of uncultured piezophiles across a range of temperatures, including a vast majority of psychropiezophiles. Despite the small number of strict piezophiles currently in culture, environmental studies suggest that life can easily accommodate high pressures, and studies on piezotolerant strains have demonstrated that life can survive brief exposures up to 2,000 MPa. Under these extreme conditions, cells have been shown to be metabolically active in fluid inclusions found in ice-VI crystals within diamond anvil cells.

21(Hyper)piezophiles have adapted to extreme pressures through various strategies. In particular, the cell membrane is packed with more unsaturated fatty acids to increase membrane fluidity at high pressures. Other adaptations could include upregulation chaperone-encoding genes, modification of the respiratory chain, expression of different porins, and production of osmolytes. Several detailed reviews on piezophile adaptation strategies are available, including,,, and.

22In contrast to high pressure environments, the low pressure found at high altitude in mountain formations (0.0033 MPa at the summit of Mount Everest) is unlikely to affect microbial survival per se, and the lowest pressure is found in space vacuum or low Earth orbit (10-13 to 10-10 MPa). Despite this, several prokaryotes, fungi, and lichen can survive exposure for several months to years under space conditions, due to sporulation or formation of biofilms. It is possible that the top layer of a biofilm protects the lower layers, enabling the survival of microorganisms under space conditions. For example, Deinococcus aetherius ST survived a 1-year exposure to space conditions only when ≥500 μm cell layer was utilized. However, longer exposure to space vacuum can cause detrimental effects, such as dehydration and DNA denaturation, and likely requires pre-dried microbial spores or biofilm within a protective substance (e.g., sugars or buffer salts). For more information, have written a detailed review on space condition effects on microorganisms.

23The effects of pressure on microbial community composition can be observed most obviously in deep-sea environments. However, it is likely that other parameters dominate as the major contributors to community composition and abundances, such as salinity, temperature, oxygen concentrations, and UV radiation, rather than pressure. In contrast to deep-sea environments, there have been few studies examining the microbial community diversity with increasing elevation, where surface air pressure decreases with altitude. However, it is still likely that other parameters affect microorganisms, as suggested by the change in bacterial diversity with elevation at Mount Fuji (Japan). The highest bacterial diversity was observed at 2,500 m, along the tree line, and declined toward ∼3,700 m (near the summit), where extreme temperatures, UV radiation, and a lack of nutrients likely affected the microbial community more significantly than pressure changes. In addition, the Earth’s atmosphere is a unique ecosystem that enables the distribution of microorganisms (∼102–105 cells/mL in cloud or fog) through aerosolization. In the atmosphere, microorganisms have to contend with multiple hazards, including UV-C and cosmic radiation, low temperatures, desiccation, and oxidants, and it is unlikely that decreasing pressure plays the most significant role in microbial community diversity. Under these conditions, sporulation, resting stages, and biofilm formation are strategies used to withstand the multiple extremes.

Radiation

24Radiation sources include UV radiation, X-rays, gamma rays and more generally, cosmic rays. These different types of ionizing radiation, in particular UV and gamma rays, can impact microbial cells via direct and indirect (e.g., the formation of reactive oxygen species) mechanisms. The reactive oxygen species can then damage DNA, proteins, lipids, and RNA, in addition to initiating Fenton-type reactions within the cell due to the release of Fe2+ from Fe-S clusters. Radiation-resistant microorganisms have been shown to resist up to 30 kGy of γ-radiation, in the case of a thermophilic bacterium Thermococcus gammatolerans EJ3 and a mesophilic bacterium Deinococcus hohokamensis and 100–1000 J/m2 of UV254, in a xerotolerant bacterium Psychrobacter pacificensis L0S3S-03b. One of the first radiation-resistant microorganisms isolated was Deinococcus radiodurans, which has been well-studied and regarded as a model organism for understanding radiation tolerance. Additionally, these microorganisms are often polyextremophiles (Table 4).

25Many ecosystems on Earth are affected by some type of radiation, with the most extreme radiation emanating from human-made radioactive-contaminated sites. These range from 0.5 Bq/kg at the Great Lakes, United States to 109 Bq/kg at Hanford Site in Richland, WA, United States. Radiation can additionally be found in subsurface environments, due to the radioactive decay of radiogenic isotopes (e.g., 238U, 232Th, and 40K), which could also be responsible for radiolytic hydrogen production, potentially supporting in situ microbial productivity. Indeed, a hyperthermophilic and radiation-tolerant archaeon was isolated (Thermococcus gammatolerans EJ3) from a deep-sea hydrothermal environment located at the East Pacific Rise, where natural radioactivity occurs (210Pb, 210Po, 222Rn).

26There are several isolated microorganisms which can survive exposure to extreme radiation (kGy), including exposure to space conditions for hundreds of days. UV radiation likely influenced the evolution of life, especially during the Archean, when the ozone layer had yet to develop in the upper atmosphere due to a lack of atmospheric O2. During this time, there were also intervals in which a photochemically produced organic haze would form, creating a UV shield. As such, the earliest life would have to contend with periods of intense UV radiation until enough O2 was produced by oxygenic phototrophs after the Great Oxidation Event (ca. 2.8–2.4 Ga). Through photochemical reactions at short UV radiation wavelengths (<242 nm), a protective ozone layer could be established, thus preventing a significant amount of short wavelength (<290 nm) radiation from penetrating to the surface. It is likely that microorganisms had to develop the necessary resistance to both UV and ionizing radiation. Indeed, model simulations demonstrate that the 200–300 nm wavelength range were several orders of magnitude higher about 4–3.5 Ga compared to current levels, and as mentioned previously T. gammatolerans EJ3 was isolated from an environment with natural radioactivity. Microbial adaptions to radiation include more genome copies for genome redundancy (, chapter 2), changes in DNA repair functions, a condensed nucleoid (, chapter 2), utilization of smaller amino acids, accumulation of Mn(II), production of pigments, and more, as described elsewhere. These adaptations are seen throughout the microbial tree of life; for example, two mutants of Halobacterium sp. NRC-1, which can tolerate extreme radiation levels (LD50 > 11 kGy), had upregulation of a protein complex known to be involved in DNA repair, replication and recombination. This complex is closely related to the archaeal and eukaryotic protein known as RPA (replication protein A) and to the bacterial protein SSB (single-strand DNA-binding protein). Although radiation resistance has been observed throughout Archaea, Bacteria, and Eukarya, the origins and evolution of such adaptations to radiation has yet to be determined.

Potential Expanded Ranges for Life

27Earth’s ecosystems often have wider ranges for each of the environmental parameters considered in this review compared to the current known limits for life (Figure 2). As described in the previous sections, the physical and chemical conditions of Earth’s environments exhibit a wide range, much of which, but not all, has been shown to be exploited by microbial life. Since the first extremophile discoveries in 1969, each decade of exploration has broadened our view of the boundaries of microbial environmental habitability. Therefore, it is likely that the true limits of life have yet to be found. For example, observed limits for temperature are -20–130°C, the theoretical temperature limit is considered to be between -40 and 150°C due to decreasing metabolic rates at -40°C (∼100 million years to turn over all of the cellular carbon; ) and the denaturation of cellular components is at 150°C ( and references therein). The ability of life to adapt and thrive under extreme conditions can be further supported by the analysis of the communities adapted to pH changes caused by human activity, including the dumping of mine drainage and steel slag. Earth’s natural ecosystems have a pH range of 0.02–12.5, but contaminated sites extend the range to pH -3.6–13.3 and have observable microbial communities (Table 2). Similar to pH, the current pressure range of microbial life (Prange 0.1–125 MPa) extends beyond that of Earth’s surface ecosystems (Prange 0.1–112 MPa), demonstrating life can resist more extreme values of both low and high pressure (see section “Pressure”). Similarly, microorganisms living in extreme salinity (salinitylife = 0–35%, salinityEarth = 0–50%) also need to contend with water activity. As mentioned previously, the lowest aw for life is currently estimated ∼0.611 aw, but microbial life surpassed this water activity limit in DHABs (∼0.4 aw) (see section “Salinity and Water Activity”).

28Although there are many (poly)extremophiles currently in culture (see Table 4 for some examples of notable polyextremophiles), data concerning the ability to withstand multiple stressors are extremely limited. Moreover, the number of cultured microorganisms is tiny if compared to the diversity of uncultured clades. The number of uncultured microorganisms at the genus level has been recently estimated to be on average 7.3 × 1029, with ∼81% of microbial cells in environments such as the terrestrial subsurface, hypersaline environments, marine sediment, hot springs, and hydrothermal vents. These uncultivated microorganisms are very likely to include (poly)extremophiles and will aid in expanding our understanding of the boundary conditions of life.

Can Life Originate, Evolve, or Survive on Other Planetary Bodies?

29Different classification schemes have been published to describe planetary bodies based on their ‘habitability’ (e.g.,;; ). Several studies have also demonstrated the growth of microorganisms under lab-simulated planetary conditions, including Mars-like and Enceladus-like conditions. In this context, defining the boundary limits of life on Earth is a crucial step in identifying the conditions likely to originate or support life on other planetary bodies. Therefore, studies on the limits of life are important to understand four areas: (1) the potential for panspermia, (2) forward contamination due to human exploration ventures, (3) planetary colonization by humans, and (4) the exploration of extinct and extant life. In this review, we outline the physical and chemical boundary conditions of Earth’s environments and those of life on Earth and compare them to the conditions observed on other planetary bodies in order to discuss whether life could originate, evolve, or survive elsewhere in our solar system and beyond.

30Similar to Earth, other planetary bodies might have different environments with varying ranges for each parameter. Since our knowledge of individual niches or habitats is extremely limited for other planetary bodies, we considered the range of each parameter (temperature, salinity, pH, and pressure) across three planetary layers: (1) atmosphere, (2) surface, and (3) subsurface (Table 5). Many planetary bodies studied thus far have the potential for extinct or extant life, based on our knowledge of life on Earth. Depending on the planetary body, different (poly)extremophiles could persist. For example, halopsychrophiles might be able to persist on Titan, Ceres, and Europa, which likely have saline subsurface oceans, and also on Mars which could have Cl-rich subsurface brines. These lifeforms would also need to withstand high pressures. For example, the hydrostatic pressure of the subsurface ocean at Titan ranges from 140 to 800 MPa. While such pressures are beyond the range of the most extreme cultured piezophile on Earth (Thermococcus piezophilus, Pmax = 125 MPa), microorganisms have successfully been exposed to pressures up to 2,000 MPa and found to be metabolically active in fluid inclusions within type-IV ice. Based on these observations it is possible that other planetary bodies may be within reach for Earth-based life (Table 5), including Enceladus (Pmax = 50 MPa; ) and Europa (Pmax = 30 MPa; ).

31The atmospheres of some planetary bodies could potentially harbor life as well. In particular, the upper-to-middle cloud layers of Venus (0–60°C; pH∼0) might be suitable for thermo- or psychro-acidophilic microorganisms (Table 4). Titan also has a dense atmosphere, but it is extremely cold (-183 – -78°C) and life on Earth can only metabolize at temperatures greater than -20°C. Other planetary bodies presented in Table 5 have transient or tenuous atmospheres that have extremely low pressures and likely cannot support life. In comparison, on Earth, microorganisms have been observed and cultured from the upper atmosphere, although stresses such as UV-C radiation, low temperatures, and oxidants make it difficult to survive. Microorganisms, in particular psychrophiles, with the capability of biofilm formation, clumping, and repair systems are more likely to tolerate Earth’s atmospheric conditions. Similar strategies may be needed on other planetary bodies.

32The surface of other planetary bodies, such as Ceres, Europa, and Mars, experience high levels of radiation, and thus, may be unsuitable to support life. UV radiation is damaging for Earth-based life, and several studies have shown that there is a 99% loss in viability for microorganisms placed under Mars-like surface conditions, with UV-C as the most harmful source. However, shielding from UV-C radiation increases the chance of survival and includes shielding by atmospheric dust or burial. Shielding is also necessary against charged particle radiation and can be achieved by burial at only centimeter depths below the surface. Indeed, the harsh radiation exposed to Europa’s surface inside the Jovian magnetosphere is predicted to only penetrate about 1–20 cm below the surface of Europa, as modeled by.

33Solar and galactic cosmic rays (high-energy particles with energies from 10 MeV to >10 GeV) present challenges to life on the surface and near-surface of Mars and other planetary bodies. However, any subsurface aquifer deeper than a few meters would be protected from damaging radiation. calculated the galactic cosmic ray dosage rates and the corresponding survival times (which they defined as a million-fold decrease in cell number) of characteristic microbes at different depths in Mars’s subsurface. At the surface, E. coli has a survival time of 1,200 years, while at 20-m depth, that survival time jumps to 1.5 × 108 years. Compared to E. coli, D. radiodurans has survival times an order of magnitude longer. These survival times are, in fact, lower limits in light of recent measurements by the Radiation Assessment Detector onboard the Mars Science Laboratory, which found that the actual dose rate at Gale Crater (76 mGy year-1) is a factor of 2 lower than that modeled by.

34With respect to cosmic rays, early Mars would have provided more favorable environments: Mars’s ancient dynamo may have produced a global magnetic field on the order of that of the present-day Earth, and a thicker atmosphere would have also provided significantly impeded a flux of high-energy particles. found that, with an atmosphere 100 times as thick, the dose rate at the surface decreases to ∼0.3–20% of its present-day value.

35In addition to radiation, the surface of other planetary bodies is generally extremely cold. The minimum estimated temperature all planetary bodies listed in Table 5, except for Venus, ranges from -138°C (Mars) to -233°C (Enceladus) while the maximum estimated temperature ranges from -179°C (Titan) to 30°C (Mars). In accordance, the average temperature of satellites that are potential analogs to Earth is much less than -5°C, with many satellites likely experiencing wide temperature variation. This indicates the physiology of radiation-tolerant psychrophiles is important for understanding the potential of life on the surface of other planetary bodies, such as the production of a fibril network, cell aggregation, and cold shock proteins.

36This suggests the subsurface is one of the most important locations in the search for extinct and extant extraterrestrial life. On Earth alone, the subsurface is estimated to house 50–87% of the Earth’s microorganisms. The subsurface of other planetary bodies is potentially warmer than the surface and atmosphere (Table 5), influenced by geothermal processes [e.g., on Mars], thermal convection [e.g., on Enceladus and Titan] and radiolysis [e.g., on Mars]. Several planetary bodies (Enceladus, Titan, Ceres, and Europa) likely have subsurface oceans, and Mars could potentially have a limited supply of groundwater. Potential communities in these extraterrestrial subsurface environments are unlikely to be supported by surface exports of organic carbon like on our planet, but rather by in situ production fueled by H2 and abiotic CH4. The abiotic production of H2 can occur through a variety of mechanisms, including the radiolysis of water and serpentinization at both high and low temperatures.

37Serpentinization consists of water-rock interactions involving the hydration of Fe2+-rich minerals (primarily olivines), resulting in alkaline pH, production of H2 and potentially low-molecular weight organic carbon (e.g., formate, methane and a wide variety of other organic compounds). Thus, serpentinization may have played a role in the origins of life on Earth and perhaps on icy worlds as well. Several planetary bodies could have ongoing serpentinization in a subsurface ocean, including Enceladus, Titan, Ceres, and Europa (Table 5), and serpentinization reactions could be widespread in the cosmos. Mars might also have serpentinization occurring in the subsurface or had serpentinization occurring millions of years ago, as indicated by the observation of hydrated minerals, such as serpentine phases, on the surface of Mars. Serpentinite-hosted sites on planetary bodies could likely support chemoautotrophic life, such as methanogens. For example, the piezotolerant thermophile Methanothermococcus okinawensis was capable of growing under Enceladus-like conditions up to 5 MPa, and the thermophilic methanogen, Methanothermobacter wolfeii, could survive subsurface Mars-like conditions across pH 5–9, pressure 0.1–122 MPa, and temperature at 55°C. The 55°C temperature corresponds to a Martian depth of 1–30 km and 10–304 MPa.

38In contrast to serpentinization, radiolysis consists of radionuclides decay, such as uranium, thorium, and radioactive potassium, decomposing water molecules into oxidizing radicals that then react with oxidizable substrates, such as pyrite, generating the necessary chemical energy for life to survive. For example, the sulfate-reducing bacterium Candidatus Desulforudis audaxviator is the only species observed in fracture fluids at depths > 1.5 km (Mponeng mine, Johannesburg, South Africa) and is likely influenced by the radiolytic production of such chemical species as H2 and sulfate. It is possible that radiolysis could support such life on other planetary bodies, including the Europan ocean and the martian subsurface.

39It is important to note that the presence of liquid water (or other liquid solvent) is the main indicator to consider the possibility of extinct or extant life on a planetary body. Planetary bodies with low water activity (aw < 0.6, see section “Salinity and Water Activity”) may not have the capability to harbor life. In places with low water activity, desiccation-tolerance could become an important factor in determining the survivability of organisms, coupled with the transient availability of water over time (either by precipitation, moisture, fog, or atmospheric humidity). For example, desiccation tolerant organisms may be able to survive under Mars-like surface conditions.

40While it is possible to use our knowledge of the boundary conditions of Earth’s life to map possible habitable environments on other planetary bodies, the discussion regarding the potential for life to originate elsewhere remains more elusive. Given the limited understanding of the processes that have led to life on our planet, discussions regarding the conditions under which life might originate on other planets remains rather speculative. As suggested previously, we might assume only planets possessing boundary conditions encompassing Earth’s biospace (Figure 2) and/or having all fundamental life requirements (e.g., energy source, solvent and building blocks) might be generative for life. An additional point to keep in mind while discussing the origin—and long-term persistence—of life on a planetary body is the necessity of elemental cycling on planetary scales, a role often accomplished on our planet by a combination of geological and biological processes on our planet linked by a complex set of feedback processes over time.

Future Directions and Outlook

41Extremophiles have pushed our understanding of the boundaries of life in all directions since they were first discovered. As already highlighted by and by the data presented in Tables 3, 4, an analysis of cultured extremophiles highlights that the majority of organisms in culture are in fact polyextremophiles. Despite this, there is a fundamental lack of studies addressing the tolerance of microorganisms to multiple extremes, potentially hindering our understanding of the limits of life. In the past 50 years of extremophile research it has become apparent that the limit of life varies when organisms face co-occurring multiple extremes. For example, the upper limit of life has been raised beyond 100°C when high pressure was also present. Future research will need to focus more on the interaction factor between multiple parameters.

42While considering the basic requirements of life discussed in the introduction (namely, energy, solvent, and building blocks), it is possible that the true limits of life are actually controlled by practical implications of these requirements. For example, the current theoretical limits of life regarding temperature, pressure, and salinity are directly linked to the water activity or the stability of biological molecules under such conditions. In the search of life’s true limits, it is therefore important to consider the effect (and combined effects) of any parameters directly controlling the availability of water, both at the community and subcellular level, and the stability of macromolecules.

43The comparative and historical analysis of the limits of Earth’s life provides insight into the epistemology of life’s boundary research. Despite ongoing scientific investigations of our planet for most of recorded human history, we still find life in unexpected places, and given the number of Earth ecosystems that still need to be explored in detail, we expect the current boundary of life to be pushed even further. Comparing Earth’s parameter space with the biospace of Earth’s life (Figure 2), one can hypothesize that life might, indeed, have adapted to occupy nearly all available planetary niches, even transiently. Taken together, these observations suggest that the true shape of the terrestrial biosphere remains undefined. Moreover, the astonishing diversity of planetary bodies and exoplanets will most likely expand the combinatorial space of environmental conditions, allowing us to speculate wildly about possible extraterrestrial lifeforms.

44While considering the possibility for life to originate and exist on other planetary bodies, it is important to consider the variability of Earth local conditions when compared to the planetary mean (Tables 2, 5). The majority of parameters considered in this review are unlikely to be extreme over an entire planet, and local or transient conditions might still support life. An outstanding example are communities present in microbialites in the Atacama Desert, where seasonal water deliquescence on salt grains was sufficient to sustain a productive and diverse community. Similarly, Recurring Slope Lineae on the surface of Mars are an extraterrestrial example of a transient condition in which the presence of hydrated salts and seasonality suggests a role for water, albeit limited. Therefore, it is unlikely that time-limited, coarse-grained observation of any extraterrestrial environment will be enough to definitely rule out the existence of life or conditions within the boundary space of Earth life, at least transiently.

45Whether or not other planetary bodies such as Mars, Enceladus, or Europa could or did support life, the search for Earth’s life true limits will inform our exploration of space and could provide insight into processes that have led to the origin of life on our planet.

Author Contributions

46NM conducted literature search, created figures, and wrote the manuscript. HA, DB, JF-B, SZ, and MW conducted literature search and wrote the manuscript. DG devised the topic, supervised manuscript structure and data collection, conducted literature search, created figures, and wrote the manuscript.

Conflict of Interest Statement

47The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References 316

1.
Airey M. W. Mather T. A. Pyle D. M. Ghail R. C. (2017 ). The distribution of volcanism in the Beta-Atla-Themis region of Venus: its relationship to rifting and implications for global tectonic regimes. J. Geophys. Res. Planets 122 1626–1649.
Not in our library10.1002/2016je005205
2.
Aislabie J. M. Chhour K. L. Saul D. J. Miyauchi S. Ayton J. Paetzold R. F. (2006 ). Dominant bacteria in soils of Marble Point and Wright Valley, Victoria Land, Antarctica. Soil Biol. Biochem. 38 3041–3056.
Not in our library10.1016/j.soilbio.2006.02.018
3.
Alazard D. Dukan S. Urios A. Verhé F. Bouabida N. Morel F. (2003 ). Desulfovibrio hydrothermalis sp. nov., a novel sulfate-reducing bacterium isolated from hydrothermal vents. Int. J. Syst. Evol. Microbiol. 53 173–178.
Not in our library10.1099/ijs.0.02323-0
4.
Alcaide M. Stogios P. J. Lafraya Á. Tchigvintsev A. Flick R. Bargiela R. (2015 ). Pressure adaptation is linked to thermal adaptation in salt-saturated marine habitats. Environ. Microbiol. 17 332–345.
Not in our library10.1111/1462-2920.12660
5.
Altair T. De Avellar M. G. B. Rodrigues F. Galante D. (2018 ). Microbial habitability of Europa sustained by radioactive sources. Sci. Rep. 8:260.
Not in our library10.1038/s41598-017-18470-z
6.
Amato P. Parazols M. Sancelme M. Laj P. Mailhot G. Delort A. M. (2007 ). Microorganisms isolated from the water phase of tropospheric clouds at the Puy de Dôme: major groups and growth abilities at low temperatures. FEMS Microbiol. Ecol. 59 242–254.
Not in our library10.1111/j.1574-6941.2006.00199.x
7.
Amend J. P. Shock E. L. (2001 ). Energetics of overall metabolic reaction of thermophilic and hyperthermophylic Archaea and Bacteria. FEMS Microbiol. Rev. 25 175–243.
Not in our library10.1111/j.1574-6976.2001.tb00576.x
8.
Anitori R. P. (2012 ). Extremophiles: Microbiology and Biotechnology. Poole: Caister Academic Press.
Not in our library
9.
Arney G. Domagal-Goldman S. D. Meadows V. S. Wolf E. T. Schwieterman E. Charnay B. (2016 ). the pale orange dot: the spectrum and habitability of Hazy Archean Earth. Astrobiology 16 873–899.
Not in our library10.1089/ast.2015.1422
10.
Aston J. E. Peyton B. M. (2007 ). Response of Halomonas campisalis to saline stress: changes in growth kinetics, compatible solute production and membrane phospholipid fatty acid composition. FEMS Microbiol. Lett. 274 196–203.
Not in our library10.1111/j.1574-6968.2007.00851.x
11.
Babu P. Chandel A. K. Singh O. V. (2015 ). Extremophiles and Their Applications in Medical Processes. Berlin: Springer
Not in our library10.1007/978-3-319-12808-5
12.
Baker B. J. Banfield J. F. (2003 ). Microbial communities in acid mine drainage. FEMS Microbiol. Ecol. 44 139–152.
Not in our library10.1016/s0168-6496(03)00028-x
13.
Baker-Austin C. Dopson M. (2007 ). Life in acid: pH homeostasis in acidophiles. Trends Microbiol. 15 165–171.
Not in our library10.1016/j.tim.2007.02.005
14.
Baland R. M. Tobie G. Lefèvre A. Van Hoolst T. (2014 ). Titan’s internal structure inferred from its gravity field, shape, and rotation state. Icarus 237 29–41.
Not in our library10.1016/j.icarus.2014.04.007
15.
Barbier B. Chabin A. Chaput D. Brack A. (1998 ). Photochemical processing of amino acids in Earth orbit. Planet. Space Sci. 46 391–398.
Not in our library10.1016/s0032-0633(97)00150-5
16.
Bartlett D. H. Eloe E. A. Lauro F. M. (2007 ). “Microbial Adaptation to High Pressure,” in Physiology and Biochemistry of Extremophiles eds Charles G. Nicolas G. (Washington, DC: American Society of Microbiology) 333–348.
Not in our library10.1128/9781555815813.ch25
17.
Basilevsky A. T. Head J. W. (2003 ). The surface of Venus. Rep. Prog. Phys. 66 1699–1734.
Not in our library10.1088/0034-4885/66/10/r04
18.
Becker K. Langseth M. G. Hyndman R. D. (1984 ). “5. Temperature measurements in Hole 395A, Leg 78B,” in Initial Reports of the Deep Sea Drilling Project eds Hyndman R. D. Salisbury M. H. (Washington, DC: U.S. Govt. Printing Office) 689–698.
Not in our library10.2973/dsdp.proc.78b.105.1984
19.
Bertaux J.-L. Vandaele A.-C. Korablev O. Villard E. Fedorova A. Fussen D. (2007 ). A warm layer in Venus’ cryosphere and high-altitude measurements of HF, HCl, H2O and HDO. Nature 450 646–649.
Not in our library10.1038/nature05974
20.
Bertrand J. C. Brochier-Armanet C. Gouy M. Westall F. (2015 ). “For three billion years, microorganisms were the only inhabitants of the earth,” in Environmental Microbiology: Fundamentals and Applications eds Bertrand J. Caumette P. Lebaron P. Matheron R. Normand P. Sime Ngando T. (Dordrecht: Springer) 25–71.
Not in our library10.1007/978-94-017-9118-2_4
21.
Blum J. S. Han S. Lanoil B. Saltikov C. Witte B. Tabita F. R. (2009 ). Ecophysiology of “Halarsenatibacter silvermanii” strain SLAS-1 T, gen. nov., sp. nov., a facultative chemoautotrophic arsenate respirer from salt-saturated Searles Lake, California. Appl. Environ. Microbiol. 75 1950–1960.
Not in our library10.1128/aem.02614-08
22.
Brassé C. Buch A. Coll P. Raulin F. (2017 ). Low-temperature alkaline pH hydrolysis of oxygen-free Titan Tholins: carbonates’ Impact. Astrobiology 17 8–26.
Not in our library10.1089/ast.2016.1524
23.
Brock T. D. Freeze H. (1969 ). Thermus aquaticus gen. nov. and sp. nov., a non-sporulating extreme thermophile. J. Bacteriol. 98 289–297.
Not in our library10.1128/jb.98.1.289-297.1969
24.
Byrne R. T. Klingele A. J. Cabot E. L. Schackwitz W. S. Martin J. A. Martin J. (2014 ). Evolution of extreme resistance to ionizing radiation via genetic adaptation of DNA repair. eLife 3:e01322.
Not in our library10.7554/elife.01322
25.
Caldwell M. M. Teramura A. H. Tevini M. (1989 ). The changing solar ultraviolet climate and the ecological consequences for higher plants. Trends Ecol. Evol. 4 363–367.
Not in our library10.1016/0169-5347(89)90100-6
26.
Capece M. C. Clark E. Saleh J. K. Halford D. Heinl N. Hoskins S. (2013 ). “Polyextremophiles and the constraints for terrestrial habitability,” in Polyextremophiles. Cellular Origin, Life in Extreme Habitats and Astrobiology eds Seckbach J. Oren A. Stan-Lotter H. (Dordrecht: Springer).
Not in our library
27.
Cassidy T. A. Paranicas C. P. Shirley J. H. Dalton J. B. Teolis B. D. Johnson R. E. (2013 ). Magnetospheric ion sputtering and water ice grain size at Europa. Planet. Space Sci. 77 64–73.
Not in our library10.1016/j.pss.2012.07.008
28.
Castillo-Rogez J. Neveu M. McSween H. Y. Fu R. R. Toplis M. J. Prettyman T. (2018 ). Insights into Ceres’s evolution from surface composition. Meteorit. Planet. Sci. 53 1820–1843.
Not in our library10.1111/maps.13181
29.
Chan C. S. Chan K. G. Ee R. Hong K. W. Urbieta M. S. Donati E. R. (2017 ). Effects of physiochemical factors on prokaryotic Biodiversity in Malaysian circumneutral hot springs. Front. Microbiol. 8:1252.
Not in our library10.3389/fmicb.2017.01252
30.
Chivian D. Brodie E. L. Alm E. J. Culley D. E. Dehal P. S. DeSantis T. Z. (2008 ). Environmental genomics reveals a single-species ecosystem deep within earth. Science 322 275–278.
Not in our library10.1126/science.1155495
31.
Chopra A. Lineweaver C. H. (2016 ). The case for a Gaian bottleneck: the biology of habitability. Astrobiology 16 7–22.
Not in our library10.1089/ast.2015.1387
32.
Chyba C. Phillips C. (2001 ). Possible ecosystems and the search for life on Europa. Proc. Natl. Acad. Sci. U.S.A. 98 801–804.
Not in our library10.1073/pnas.98.3.801
33.
A Low Temperature Limit for Life on Earth. · 2013
Not checked
34.
Clifford S. M. Lasue J. Heggy E. Boisson J. McGovern P. Max M. D. (2010 ). Depth of the Martian cryosphere: revised estimates and implications for the existence and detection of subpermafrost groundwater. J. Geophys. Res. 115 E07001
Not in our library10.1029/2009je003462
35.
Cnossen I. Sanz-Forcada J. Favata F. Witasse O. Zegers T. Arnold N. F. (2007 ). Habitat of early life: solar X-ray and UV radiation at Earth’s surface 4–3.5 billion years ago. J. Geophys. Res. 112:E02008
Not in our library10.1029/2006je002784
36.
Cockell C. S. (1999 ). Life on Venus. Planet. Space Sci. 47 1487–1501.
Not in our library10.1016/s0032-0633(99)00036-7
37.
Cockell C. S. Lee P. Osinski G. Horneck G. Broady P. (2002 ). Impact-induced microbial endolithic habitats. Meteorit. Planet. Sci. 37 1287–1298.
Not in our library10.1111/j.1945-5100.2002.tb01029.x
38.
Cockell C. S. Raven J. A. (2007 ). Ozone and life on the Archaean Earth. Philos. Trans. A Math. Phys. Eng. Sci. 365 1889–1901.
Not in our library10.1098/rsta.2007.2049
39.
Cockell C. S. Schuerger A. C. Billi D. Friedmann E. I. Panitz C. (2005 ). Effects of a simulated martian uv flux on the cyanobacterium, Chroococcidiopsis. Astrobiology 5 127–140.
Not in our library10.1089/ast.2005.5.127
40.
Coker J. A. (2016 ). Extremophiles and biotechnology: current uses and prospects. F1000Res. 5:F1000 Faculty Rev-396.
Not in our library10.12688/f1000research.7432.1
41.
Cole J. K. Peacock J. P. Dodsworth J. A. Williams A. J. Thompson D. B. Dong H. (2013 ). Sediment microbial communities in Great Boiling Spring are controlled by temperature and distinct from water communities. ISME J. 7 718–729.
Not in our library10.1038/ismej.2012.157
42.
Colman D. R. Poudel S. Hamilton T. L. Havig J. R. Selensky M. J. Shock E. L. (2018 ). Geobiological feedbacks and the evolution of thermoacidophiles. ISME J. 12 225–236.
Not in our library10.1038/ismej.2017.162
43.
Confalonieri F. Sommer S. (2011 ). Bacterial and archaeal resistance to ionizing radiation. J. Phys. Conf. Ser. 261:012005
Not in our library10.1088/1742-6596/261/1/012005
44.
Cordier D. Garciá-Sánchez F. Justo-Garciá D. N. Liger-Belair G. (2017 ). Bubble streams in Titan’s seas as a product of liquid N2 + CH4 + C2H6 cryogenic mixture. Nat. Astron. 1:0102
Not in our library10.1038/s41550-017-0102
45.
Czop M. Motyka J. Sracek O. Szuwarzyñski M. (2011 ). Geochemistry of the hyperalkaline Gorka pit lake (pH > 13) in the Chrzanow region, southern Poland. Water Air Soil Pollut. 214 423–434.
Not in our library10.1007/s11270-010-0433-x
46.
Dalmasso C. Oger P. Selva G. Courtine D. L’Haridon S. Garlaschelli A. (2016 ). Thermococcus piezophilus sp. nov., a novel hyperthermophilic and piezophilic archaeon with a broad pressure range for growth, isolated from a deepest hydrothermal vent at the Mid-Cayman Rise. Syst. Appl. Microbiol. 39 440–444.
Not in our library10.1016/j.syapm.2016.08.003
47.
Daly M. J. Gaidamakova E. K. Matrosova V. Y. Vasilenko A. Zhai M. Venkateswaran A. (2004 ). Accumulation of Mn(II) in Deinococcus radiodurans facilitates gamma-radiation resistance. Science 306 1025–1028.
Not in our library10.1126/science.1103185
48.
Deep-Sea Biodiversity in the Mediterranean Sea: The Known, the Unknown, and the Unknowable · 2010
No notice
49.
Dartnell L. R. Desorgher L. Ward J. M. Coates A. J. (2007 ). Modelling the surface and subsurface Martian radiation environment: implications for astrobiology. Geophys. Res. Lett. 34 4–9.
Not in our library10.1029/2006gl027494
50.
DasSarma P. DasSarma S. (2018 ). Survival of microbes in Earth’s stratosphere. Curr. Opin. Microbiol. 43 24–30.
Not in our library10.1016/j.mib.2017.11.002
51.
DasSarma S. DasSarma P. (2017 ). “Halophiles,” in eLS (Chichester: John Wiley & Sons) 1–13.
Not in our library10.1002/9780470015902.a0000394.pub4
52.
Davila A. F. Gómez-Silva B. de los Rios A. Ascaso C. Olivares H. McKay C. P. (2008 ). Facilitation of endolithic microbial survival in the hyperarid core of the Atacam Desert by mineral deliquescence. J. Geophys. Res. Biogeosci. 113:G1
Not in our library10.1029/2007jg000561
53.
de Kok R. Irwin P. G. J. Teanby N. A. Lellouch E. Bézard B. Vinatier S. (2007 ). Oxygen compounds in Titan’s stratosphere as observed by Cassini CIRS. Icarus 186 354–363.
Not in our library10.1016/j.icarus.2006.09.016
54.
De Vera J. P. Boettger U. Noetzel R. de la T. Sánchez F. J. Grunow D. (2012 ). Supporting Mars exploration: BIOMEX in Low Earth Orbit and further astrobiological studies on the Moon using Raman and PanCam technology. Planet. Space Sci. 74 103–110.
Not in our library10.1016/j.pss.2012.06.010
55.
Delmelle P. Bernard A. (1994 ). Geochemistry, mineralogy, and chemical modeling of the acid crater lake of Kawah Ijen Volcano, Indonesia. Geochim. Cosmochim. Acta 58 2445–2460.
Not in our library10.1016/0016-7037(94)90023-x
56.
Delort A. M. Vaïtilingom M. Amato P. Sancelme M. Parazols M. Mailhot G. (2010 ). A short overview of the microbial population in clouds: potential roles in atmospheric chemistry and nucleation processes. Atmos. Res. 98 249–260.
Not in our library10.1016/j.atmosres.2010.07.004
57.
Deming J. W. (2007 ). “Life in ice formations at very cold temperatures,” in Physiology and Biochemistry of Extremophiles eds Gerday C. Glansdorff N. (Washington, DC: American Society of Microbiology) 133–144.
Not in our library10.1128/9781555815813.ch10
58.
DeVeaux L. C. Müller J. A. Smith J. Petrisko J. Wells D. P. DasSarma S. (2007 ). Extremely radiation-resistant mutants of a halophilic archaeon with increased single-stranded DNA-binding protein (RPA) gene expression. Radiat. Res. 168 507–514.
Not in our library10.1667/rr0935.1
59.
Dickson J. L. Head J. W. Levy J. S. Marchant D. R. (2013 ). Don Juan Pond, Antarctica: near-surface CaCl2-brine feeding Earth’s most saline lake and implications for Mars. Sci. Rep. 3:1166.
Not in our library10.1038/srep01166
60.
Dion P. Nautiyal C. S. Dion P. (2008 ). Microbiology of Extreme Soils. Berlin: Springer
Not in our library10.1007/978-3-540-74231-9
61.
Dose K. Bieger-Dose A. Ernst B. Feister U. Gómez-Silva B. Klein A. (2001 ). Survival of microorganisms under the extreme conditions of the Atacama desert. Orig. Life Evol. Biosph. 31 287–303.
Not in our library10.1023/a:1010788829265
62.
Dundas C. M. McEwen A. S. Chojnacki M. Milazzo M. P. Byrne S. McElwaine J. N. (2017 ). Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water. Nat. Geosci. 10 903–907.
Not in our library10.1038/s41561-017-0012-5
63.
Durvasula R. Rao D. V. S. (eds). (2018 ). “Extremophiles: from Biology to Biotechnology,” in Extremophiles (Boca Raton: Taylor & Francis, a CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa plc, 2018 (Boca Raton, FL: CRC Press) 1–18.
Not in our library10.1201/9781315154695-1
64.
Dzaugis M. Spivack A. J. D’Hondt S. (2018 ). Radiolytic H2 production in martian environments. Astrobiology 18 1137–1146.
Not in our library10.1089/ast.2017.1654
65.
Dzaugis M. E. Spivack A. J. Dunlea A. G. Murray R. W. D’Hondt S. (2016 ). Radiolytic hydrogen production in the subseafloor basaltic aquifer. Front. Microbiol. 7:76.
Not in our library10.3389/fmicb.2016.00076
66.
Edwards K. J. Bond P. L. Gihring T. M. Banfield J. F. (2000 ). An Archaeal iron-oxidizing extreme acidophile important in acid mine drainage. Science 287 1796–1799.
Not in our library10.1126/science.287.5459.1796
67.
Ehlmann B. L. Mustard J. F. Murchie S. L. (2010 ). Geologic setting of serpentine deposits on Mars. Geophys. Res. Lett. 37 1–5.
Not in our library10.1029/2010gl042596
68.
Ehresmann B. Burmeister S. Schweingruber R. F. W. Reitz G. (2011 ). Influence of higher atmospheric pressure on the Martian radiation environment: implications for possible habitability in the Noachian epoch. J. Geophys. Res. 116 1–9.
Not in our library10.1029/2011ja016616
69.
El-Demerdash M. A. Hegazy A. K. Zilay A. M. (1995 ). Vegetation-soil relationships in Tihamah coastal plains of Jazan region, Saudi Arabia. J. Arid Environ. 30 161–174.
Not in our library10.1016/s0140-1963(05)80067-9
70.
Emeis K. C. Robertson A. H. F. Richter D. (1996 ). Proceedings of the Ocean Drilling Program, Initial Reports, 160. College Station, TX: Ocean Drilling Program.
Not in our library
71.
Everroad R. C. Otaki H. Matsuura K. Haruta S. (2012 ). Diversification of bacterial community composition along a temperature gradient at a thermal spring. Microbes Environ. 27 374–381.
Not in our library10.1264/jsme2.me11350
72.
Fairén A. G. Davila A. F. Gago-Duport L. Amils R. McKay C. P. (2009 ). Stability against freezing of aqueous solutions on early Mars. Nature 459 401–404.
Not in our library10.1038/nature07978
73.
Fairén A. G. Fernández-Remolar D. Dohm J. M. Baker V. R. Amils R. (2004 ). Inhibition of carbonate synthesis in acidic oceans on early Mars. Nature 431 423–426.
Not in our library10.1038/nature02911
74.
Transcriptomic responses of Serratia liquefaciens cells grown under simulated Martian conditions of low temperature, low pressure, and CO2-enriched anoxic atmosphere · 2018
Not checked
75.
Fanale F. P. Salvail J. R. (1989 ). The water regime of asteroid (1) Ceres. Icarus 82 97–110.
Not in our library10.1016/0019-1035(89)90026-2
76.
Fang J. Zhang L. Bazylinski D. A. (2010 ). Deep-sea piezosphere and piezophiles: geomicrobiology and biogeochemistry. Trends Microbiol. 18 413–422.
Not in our library10.1016/j.tim.2010.06.006
77.
Fernández-Calviño D. Bååth E. (2010 ). Growth response of the bacterial community to pH in soils differing in pH. FEMS Microbiol. Ecol. 73 149–156.
Not in our library10.1111/j.1574-6941.2010.00873.x
78.
Ferrera I. Reysenbach A.-L. (2007 ). “Thermophiles,” in Encyclopedia of Life Sciences (Hoboken, NJ: John Wiley & Sons)
Not in our library10.1002/9780470015902.a0000406
79.
Feyhl-Buska J. Chen Y. Jia C. Wang J. X. Zhang C. L. Boyd E. S. (2016 ). Influence of growth phase, pH, and temperature on the abundance and composition of tetraether lipids in the thermoacidophile Picrophilus torridus. Front. Microbiol. 7:1323.
Not in our library10.3389/fmicb.2016.01323
80.
Finlayson C. M. Milton R. Prentice C. Davidson N. C. (eds) (2018 ). The Wetland Book II, Distribution, Description, and Conservation. Berlin: Springer.
Not in our library
81.
Flores G. E. Shakya M. Meneghin J. Yang Z. K. Seewald J. S. Geoff Wheat C. (2012 ). Inter-field variability in the microbial communities of hydrothermal vent deposits from a back-arc basin. Geobiology 10 333–346.
Not in our library10.1111/j.1472-4669.2012.00325.x
82.
Fouke B. W. (2011 ). Hot-spring Systems Geobiology: abiotic and biotic influences on travertine formation at Mammoth Hot Springs, Yellowstone National Park, USA. Sedimentology 58 170–219.
Not in our library10.1111/j.1365-3091.2010.01209.x
83.
Frank Y. A. Kadnikov V. V. Gavrilov S. N. Banks D. Gerasimchuk A. L. Podosokorskaya O. A. (2016 ). Stable and variable parts of microbial community in Siberian deep subsurface thermal aquifer system revealed in a long-term monitoring study. Front. Microbiol. 7:2101.
Not in our library10.3389/fmicb.2016.02101
84.
Fredrickson J. K. Li S. M. W. Gaidamakova E. K. Matrosova V. Y. Zhai M. Sulloway H. M. (2008 ). Protein oxidation: key to bacterial desiccation resistance? ISME J. 2 393–403.
Not in our library10.1038/ismej.2007.116
85.
Fredrickson J. K. Zachara J. M. Balkwill D. L. Kennedy D. Li S. M. W. Kostandarithes H. M. (2004 ). Geomicrobiology of high-level nuclear waste-contaminated vadose sediments at the Hanford Site Washington State. Appl. Environ. Microbiol. 70 4230–4241.
Not in our library10.1128/aem.70.7.4230-4241.2004
86.
Frösler J. Panitz C. Wingender J. Flemming H.-C. Rettberg P. (2017 ). Survival of Deinococcus geothermalis in Biofilms under Desiccation and Simulated Space and Martian Conditions. Astrobiology 17 431–447.
Not in our library10.1089/ast.2015.1431
87.
Fulchignoni M. Ferri F. Angrilli F. Ball A. J. Bar-Nun A. Barucci M. A. (2005 ). In situ measurements of the physical characteristics of Titan’s environment. Nature 438 785–791.
Not in our library10.1038/nature04314
88.
Gioia G. Chakraborty P. Marshak S. Kieffer S. W. (2007 ). Unified model of tectonics and heat transport in a frigid Enceladus. Proc. Natl. Acad. Sci. U.S.A. 104 13578–13581.
Not in our library10.1073/pnas.0706018104
89.
Giovannelli D. D’Errico G. Manini E. Yakimov M. Vetriani C. (2013 ). Diversity and phylogenetic analyses of bacteria from a shallow-water hydrothermal vent in Milos island (Greece). Front. Microbiol. 4:184.
Not in our library10.3389/fmicb.2013.00184
90.
Glein C. R. Baross J. A. Waite J. H. (2015 ). The pH of Enceladus’ ocean. Geochim. Cosmochim. Acta 162 202–219. 19553992
Not in our library10.1016/j.gca.2015.04.017
91.
Grindrod P. M. Fortes A. D. Nimmo F. Feltham D. L. Brodholt J. P. Voèadlo L. (2008 ). The long-term stability of a possible aqueous ammonium sulfate ocean inside Titan. Icarus 197 137–151.
Not in our library10.1016/j.icarus.2008.04.006
92.
Hallsworth J. E. Yakimov M. M. Golyshin P. N. Gillion J. L. M. D’Auria G. De Lima Alves F. (2007 ). Limits of life in MgCl2-containing environments: chaotropicity defines the window. Environ. Microbiol. 9 801–813.
Not in our library10.1111/j.1462-2920.2006.01212.x
93.
Hand K. P. Carlson R. W. (2015 ). Europa’s surface color suggests an ocean rich with sodium chloride. Geophys. Res. Lett. 42 3174–3178.
Not in our library10.1002/2015gl063559
94.
Hans Wedepohl K. (1995 ). The composition of the continental crust. Geochim. Cosmochim. Acta 59 1217–1232.
Not in our library10.1016/0016-7037(95)00038-2
95.
Hansen A. A. Jensen L. L. Kristoffersen T. Mikkelsen K. Merrison J. Finster K. W. (2009 ). Effects of long-term simulated Martian conditions on a freeze-dried and homogenized bacterial permafrost community. Astrobiology 9 229–240.
Not in our library10.1089/ast.2008.0244
96.
Harrison J. P. Gheeraert N. Tsigelnitskiy D. Cockell C. S. (2013 ). The limits for life under multiple extremes. Trends Microbiol. 21 204–212.
Not in our library10.1016/j.tim.2013.01.006
97.
Hassler D. M. Zeitlin C. Wimmer-schweingruber R. F. Ehresmann B. Rafkin S. Eigenbrode J. L. (2014 ). Mars’ surface radiation environment. Science 343:1244797.
Not in our library10.1126/science.1244797
98.
Hayne P. O. Aharonson O. (2015 ). Thermal stability of ice on Ceres with rough topography. J. Geophys. Res. E Planets 120 1567–1584.
Not in our library10.1002/2015je004887
99.
Hecht M. H. Kounaves S. P. Quinn R. C. West S. J. Young S. M. M. Ming D. W. (2009 ). Detection of perchlorate and the soluble chemistry of Martian soil at the phoenix lander site. Science 325 64–67.
Not in our library10.1126/science.1172466
100.
Hendrix A. R. Vilas F. Li J. Y. (2016 ). Ceres: sulfur deposits and graphitized carbon. Geophys. Res. Lett. 43 8920–8927.
Not in our library10.1002/2016gl070240
101.
Hoehler T. M. Jørgensen B. B. (2013 ). Microbial life under extreme energy limitation. Nat. Rev. Microbiol. 11 83–94.
Not in our library10.1038/nrmicro2939
102.
Holm D. A. Owen L. Ochsenwald W. L. (2017 ). Arabian Desert. Available at: https://www.britannica.com/place/Arabian-Desert
Not in our library
103.
Holm N. G. Oze C. Mousis O. Waite J. H. Guilbert-Lepoutre A. (2015 ). Serpentinization and the Formation of H2 and CH4 on Celestial Bodies (Planets, Moons, Comets). Astrobiology 15 587–600.
Not in our library10.1089/ast.2014.1188
104.
Horneck G. Klaus D. M. Mancinelli R. L. (2010 ). Space microbiology. Microbiol. Mol. Biol. Rev. 74 121–156.
Not in our library10.1128/mmbr.00016-09
105.
Hsu H. W. Postberg F. Sekine Y. Shibuya T. Kempf S. Horányi M. (2015 ). Ongoing hydrothermal activities within Enceladus. Nature 519 207–210.
Not in our library10.1038/nature14262
106.
Hug L. A. Baker B. J. Anantharaman K. Brown C. T. Probst A. J. Castelle C. J. (2016 ). A new view of the tree of life. Nat. Microbiol. 1:16048.
Not in our library10.1038/nmicrobiol.2016.48
107.
Jaakkola S. T. Ravantti J. J. Oksanen H. M. Bamford D. H. (2016 ). Buried alive: microbes from ancient halite. Trends Microbiol. 24 148–160.
Not in our library10.1016/j.tim.2015.12.002
108.
James J. J. Tiller R. L. Richards J. H. (2005 ). Multiple resources limit plant growth and function in a saline-alkaline desert community. J. Ecol. 93 113–126.
Not in our library10.1111/j.0022-0477.2004.00948.x
109.
Javor B. (1984 ). Growth potential of halophilic bacteria isolated from solar salt environments: carbon sources and salt requirements. Appl. Environ. Microbiol. 48 352–360.
Not in our library10.1128/aem.48.2.352-360.1984
110.
Jebbar M. Franzetti B. Girard E. Oger P. (2015 ). Microbial diversity and adaptation to high hydrostatic pressure in deep-sea hydrothermal vents prokaryotes. Extremophiles 19 721–740.
Not in our library10.1007/s00792-015-0760-3
111.
Jelen B. I. Giovannelli D. Falkowski P. G. (2016 ). The role of microbial electron transfer in the coevolution of the biosphere and geosphere. Annu. Rev. Microbiol. 70 45–62.
Not in our library10.1146/annurev-micro-102215-095521
112.
Jennings D. E. Cottini V. Nixon C. A. Achterberg R. K. Flasar F. M. Kunde V. G. (2016 ). Surface temperatures on Titan during northern winter and spring. Astrophys. J. 816:L17
Not in our library10.3847/2041-8205/816/1/l17
113.
Jin Q. Kirk M. F. (2018 ). pH as a primary control in environmental microbiology: 1. Thermodynamic Perspective. Front. Environ. Sci. 6:21
Not in our library10.3389/fenvs.2018.00021
114.
Johnson A. P. Pratt L. M. Vishnivetskaya T. Pfiffner S. Bryan R. A. Dadachova E. (2011 ). Extended survival of several organisms and amino acids under simulated martian surface conditions. Icarus 211 1162–1178.
Not in our library10.1016/j.icarus.2010.11.011
115.
Jolivet E. L’Haridon S. Corre E. Forterre P. Prieur D. (2003 ). Thermococcus gammatolerans sp. nov., a hyperthermophilic archeon from a deep-sea hydrothermal vent that resists ionizing radiation. Int. J. Syst. Evol. Microbiol. 53 847–851.
Not in our library10.1099/ijs.0.02503-0
116.
Jones B. F. Eugster H. P. Rettig S. L. (1977 ). Hydrochemistry of the Lake Magadi basin, Kenya. Geochim. Cosmochim. Acta 41 53–72.
Not in our library10.1016/0016-7037(77)90186-7
117.
Jones E. G. Lineweaver C. H. Clarke J. D. (2011 ). An extensive phase space for the potential martian biosphere. Astrobiology 11 1017–1033.
Not in our library10.1089/ast.2011.0660
118.
Jones R. M. Goordial J. M. Orcutt B. N. (2018 ). Low energy subsurface environments as extraterrestrial analogs. Front. Microbiol. 9:1605.
Not in our library10.3389/fmicb.2018.01605
119.
Junge K. Eicken H. Deming J. W. (2004 ). Bacterial Activity at -2 to -20°C in Arctic Wintertime Sea Ice. Appl. Environ. Microbiol. 70 550–557.
Not in our library10.1128/aem.70.1.550-557.2004
120.
Kallmeyer J. Pockalny R. Adhikari R. R. Smith D. C. D’Hondt S. (2012 ). Global distribution of microbial abundance and biomass in subseafloor sediment. Proc. Natl. Acad. Sci. U.S.A. 109 16213–16216.
Not in our library10.1073/pnas.1203849109
121.
Karbe L. (1986 ). “Hot Brines and the Deep Sea Environment,” in Red Sea eds Edwards A. J. Head S. M. (Oxford: Pergamon Press).
Not in our library
122.
Kargel J. S. Kaye J. Z. Head J. W. Marion G. M. Sassen R. Crowley J. K. (2000 ). Europa’s crust and ocean: origin, composition, and the prospects for life. Icarus 148 226–265.
Not in our library10.1006/icar.2000.6471
123.
Kashefi K. Holmes D. E. Reysenbach A. L. Lovley D. R. (2002 ). Use of Fe(III) as an electron acceptor to recover previously uncultured hyperthermophiles: Isolation and characterization of Geothermobacterium ferrireducens gen. nov., sp. nov. Appl. Environ. Microbiol. 68 1735–1742.
Not in our library10.1128/aem.68.4.1735-1742.2002
124.
Kashefi K. Lovley D. R. (2003 ). Extending the upper temperature limit for life. Science 301:934.
Not in our library10.1126/science.1086823
125.
Kattenhorn S. A. Prockter L. M. (2014 ). Evidence for subduction in the ice shell of Europa. Nat. Geosci. 7 762–767.
Not in our library10.1038/ngeo2245
126.
Kavak M. T. Karadogan S. (2012 ). Investigation of Sea Surface Temperature Variation of Lake Van Using AVHRR. https://www.researchgate.net/publication/256512293_INVESTIGATION_SEA_SURFACE_TEMPERATURE_VARIATION_OF_LAKE_VAN_USING_AVHRR
Not in our library
127.
Kelly D. P. Wood A. P. (2000 ). Reclassification of some species of Thiobacillus Acidithiobacillus gen. nov., Halothiobacillus. Int. J. Syst. Evol. Microbiol. 50 511–516.
Not in our library10.1099/00207713-50-2-511
128.
Kimura J. Kitadai N. (2015 ). Polymerization of building blocks of life on Europa and other icy moons. Astrobiology 15 430–441.
Not in our library10.1089/ast.2015.1306
129.
Kingsbury J. M. (1954 ). On the Isolation, Physiology, and Development of a Minute, Hardy, Bluegreen Alga. Ph.D. thesis, Dr. Diss. Harvard Univ.
Not in our library
130.
Knoll A. H. (2015 ). Life on a Young Planet: The First Three Billion Years of Evolution on Earth. Princeton, NJ: Princeton University Press
Not in our library10.1515/9781400866045
131.
Konn C. Charlou J. L. Donval J. P. Holm N. G. Dehairs F. Bouillon S. (2009 ). Hydrocarbons and oxidized organic compounds in hydrothermal fluids from Rainbow and Lost City ultramafic-hosted vents. Chem. Geol. 258 299–314.
Not in our library10.1016/j.chemgeo.2008.10.034
132.
Koschinsky A. Garbe-Schönberg D. Sander S. Schmidt K. Gennerich H. H. Strauss H. (2008 ). Hydrothermal venting at pressure-temperature conditions above the critical point of seawater, 5°S on the Mid-Atlantic Ridge. Geology 36 615–618.
Not in our library10.1130/g24726a.1
133.
Kottemann M. Kish A. Iloanusi C. Bjork S. DiRuggiero J. (2005 ). Physiological responses of the halophilic archaeon Halobacterium sp. strain NRC1 to desiccation and gamma irradiation. Extremophiles 9 219–227.
Not in our library10.1007/s00792-005-0437-4
134.
Krisko A. Radman M. (2013 ). Biology of extreme radiation resistance: the way of Deinococcus radiodurans. Cold Spring Harb. Perspect. Biol. 5:a012765.
Not in our library10.1101/cshperspect.a012765
135.
Krulwich T. A. Sachs G. Padan E. (2011 ). Molecular aspects of bacterial pH sensing and homeostasis. Nat. Rev. Microbiol. 9 330–343.
Not in our library10.1038/nrmicro2549
136.
Kuang J.-L. Huang L.-N. Chen L.-X. Hua Z.-S. Li S.-J. Hu M. (2013 ). Contemporary environmental variation determines microbial diversity patterns in acid mine drainage. ISME J. 7 1038–1050.
Not in our library10.1038/ismej.2012.139
137.
Küppers M. O’Rourke L. Bockelée-Morvan D. Zakharov V. Lee S. Von Allmen P. (2014 ). Localized sources of water vapour on the dwarf planet (1) Ceres. Nature 505 525–527.
Not in our library10.1038/nature12918
138.
La Duc M. T. Benardini J. N. Kempf M. J. Newcombe D. A. Lubarsky M. Venkateswaran K. (2007 ). Microbial diversity of Indian ocean hydrothermal vent plumes: microbes tolerant of desiccation. Peroxide Exposure, and Ultraviolet and γ-Irradiation. Astrobiology 7 416–431.
Not in our library10.1089/ast.2006.0060
139.
Lammer H. Bredehöft J. H. Coustenis A. Khodachenko M. L. Kaltenegger L. Grasset O. (2009 ). What makes a planet habitable? Astron. Astrophys. Rev. 17 181–249.
Not in our library10.1007/s00159-009-0019-z
140.
Lane N. Allen J. F. Martin W. (2010 ). How did LUCA make a living? Chemiosmosis in the origin of life - Lane - 2010 - BioEssays - Wiley Online Library. BioEssays 32 271–280.
Not in our library10.1002/bies.200900131
141.
Lane N. Martin W. F. (2012 ). The origin of membrane bioenergetics. Cell 151 1406–1416.
Not in our library10.1016/j.cell.2012.11.050
142.
Lang N. P. Hansen V. L. (2006 ). Venusian channel formation as a subsurface process. J. Geophys. Res. E Planets 111:E04001
Not in our library10.1029/2005je002629
143.
Langmuir D. (1971 ). The geochemistry of some carbonate ground waters in central Pennsylvania. Geochim. Cosmochim. Acta 35 1023–1045.
Not in our library10.1016/0016-7037(71)90019-6
144.
LaRowe D. E. Amend J. P. (2015 ). Power limits for microbial life. Front. Microbiol. 6:718
Not in our library10.3389/fmicb.2015.00718
145.
Lauber C. L. Hamady M. Knight R. Fierer N. (2009 ). Pyrosequencing-based assessment of soil pH as a predictor of soil bacterial community structure at the continental scale. Appl. Environ. Microbiol. 75 5111–5120.
Not in our library10.1128/aem.00335-09
146.
Lechmann S. M. Schmalholz S. M. Hetényi G. May D. A. Kaus B. J. P. (2014 ). Quantifying the impact of mechanical layering and underthrusting on the dynamics of the modern India-Asia collisional system with 3-D numerical models. J. Geophys. Res. Solid Earth 119 616–644.
Not in our library10.1002/2012jb009748
147.
Li H. Yang Q. Li J. Gao H. Li P. Zhou H. (2015 ). The impact of temperature on microbial diversity and AOA activity in the Tengchong Geothermal Field, China. Sci. Rep. 5:17056.
Not in our library10.1038/srep17056
148.
Lin L. H. Hall J. Lippmann-Pipke J. Ward J. A. Lollar B. S. DeFlaun M. (2005 ). Radiolytic H2 in continental crust: nuclear power for deep subsurface microbial communities. Geochem. Geophys. Geosyst. 6:Q07003
Not in our library10.1029/2004gc000907
149.
Phylogenetically Novel Uncultured Microbial Cells Dominate Earth Microbiomes · 2018
No notice
150.
Longstaff A. (2014 ). Astrobiology: An Introduction. Boca Raton, FL: CRC Press
Not in our library10.1201/b17880
151.
Lozupone C. A. Knight R. (2007 ). Global patterns in bacterial diversity. Proc. Natl. Acad. Sci. U.S.A. 104 11436–11440.
Not in our library10.1073/pnas.0611525104
152.
Lu J. Nogi Y. Takami H. (2001 ). Oceanobacillus iheyensis gen. nov., sp. nov., a deep-sea extremely halotolerant and alkaliphilic species isolated from a depth of 1050 m on the Iheya Ridge. FEMS Microbiol. Lett. 205 291–297.
Not in our library10.1016/s0378-1097(01)00493-1
153.
Magnabosco C. Lin L. H. Dong H. Bomberg M. Ghiorse W. Stan-Lotter H. (2018 ). The biomass and biodiversity of the continental subsurface. Nat. Geosci. 11 707–717.
Not in our library10.1038/s41561-018-0221-6
154.
Mancinelli R. L. Klovstad M. (2000 ). Martian soil and UV radiation: Microbial viability assessment on spacecraft surfaces. Planet. Space Sci. 48 1093–1097.
Not in our library10.1016/s0032-0633(00)00083-0
155.
Mantyla A. W. Reid J. L. (1983 ). Abyssal characteristics of the World Ocean waters. Deep Sea Res. Part A Oceanogr. Res. Pap. 30 805–833.
Not in our library10.1016/0198-0149(83)90002-x
156.
Mapelli F. Barozzi A. Michoud G. Merlino G. Crotti E. Borin S. (2017 ). “An updated view of the microbial diversity in deep hypersaline anoxic basins,” in Adaption of Microbial Life to Environmental Extremes 2nd Edn eds Stan-Lotter H. Fendrihan S. (Cham: Springer) 23–40.
Not in our library10.1007/978-3-319-48327-6_2
157.
Marion G. M. Kargel J. S. Catling D. C. Jakubowski S. D. (2005 ). Effects of pressure on aqueous chemical equilibria at subzero temperatures with applications to Europa. Geochim. Cosmochim. Acta 69 259–274.
Not in our library10.1016/j.gca.2004.06.024
158.
Martin A. McMinn A. (2018 ). Sea ice, extremophiles and life on extra-terrestrial ocean worlds. Int. J. Astrobiol. 17 1–16.
Not in our library10.1017/s1473550416000483
159.
Mastrogiuseppe M. Poggiali V. Hayes A. Lorenz R. Lunine J. Picardi G. (2014 ). The bathymetry of a Titan sea. Geophys. Res. Lett. 41 1432–1437.
Not in our library10.1002/2013gl058618
160.
McCollom T. M. (1999 ). Methanogenesis as a potential source of chemical energy for primary biomass production by autotrophic organisms in hydrothermal systems on Europa. J. Geophys. Res. Planets 104 30729–30742.
Not in our library10.1029/1999je001126
161.
McCollom T. M. (2016 ). Abiotic methane formation during experimental serpentinization of olivine. Proc. Natl. Acad. Sci. U.S.A. 113 13965–13970.
Not in our library10.1073/pnas.1611843113
162.
McCord T. B. Castillo-Rogez J. C. (2018 ). Ceres’s internal evolution: The view after Dawn. Meteorit. Planet. Sci. 53 1778–1792.
Not in our library10.1111/maps.13135
163.
McCord T. B. Sotin C. (2005 ). Ceres: evolution and current state. J. Geophys. Res. E Planets 110:E5. 28416725
Not in our library10.1029/2004je002244
164.
McCord T. B. Zambon F. (2019 ). The surface composition of Ceres from the Dawn mission. Icarus 318 2–13.
Not in our library10.1016/j.icarus.2018.03.004
165.
McDermott J. M. Sylva S. P. Ono S. German C. R. Seewald J. S. (2018 ). Geochemistry of fluids from Earth’s deepest ridge-crest hot-springs: piccard hydrothermal field, Mid-Cayman Rise. Geochim. Cosmochim. Acta 228 95–118.
Not in our library10.1016/j.gca.2018.01.021
166.
McDonough W. F. Sun S. S. (1995 ). The composition of the Earth. Chem. Geol. 120 223–253.
Not in our library10.1016/0009-2541(94)00140-4
167.
McEwen A. S. Ojha L. Dundas C. M. Mattson S. S. Byrne S. Wray J. J. (2011 ). Seasonal flows on warm Martian slopes. Science 333 740–743.
Not in our library10.1126/science.1204816
168.
McGrath M. A. Hansen C. J. Hendrix A. R. (2009 ). “Observations of Europa’s Tenuous Atmosphere,” in Europa Pappalardo R. T. McKinnon W. B. Khurana K. K. (Tucson, AZ: University of Arizona Press) 485–506.
Not in our library
169.
McKay C. P. (2014 ). Requirements and limits for life in the context of exoplanets. Proc. Natl. Acad. Sci. U.S.A. 111 12628–12633.
Not in our library10.1073/pnas.1304212111
170.
Titan as the Abode of Life · 2016
Not checked
171.
Meklat A. Bouras N. Zitouni A. Mathieu F. Lebrihi A. Schumann P. (2013 ). Actinopolyspora mzabensis sp. nov., a halophilic actinomycete isolated from an Algerian Saharan soil. Int. J. Syst. Evol. Microbiol. 63 3787–3792.
Not in our library10.1099/ijs.0.046649-0
172.
Microbial diversity and metabolic networks in acid mine drainage habitats · 2015
No notice
173.
Merlino G. Barozzi A. Michoud G. Ngugi D. K. Daffonchio D. (2018 ). Microbial ecology of deep-sea hypersaline anoxic basins. FEMS Microbiol. Ecol. 94
Not in our library10.1093/femsec/fiy085
174.
Mesbah N. Wiegel J. (2005 ). “Halophilic thermophiles: a novel group of extremophiles,” in Microbial Diversity: Current Perspective and Potential Applications eds Satyanarayana T. Johri B. N. (New Delhi: International Publishing House Pvt. Ltd.) 91–118
Not in our library10.1196/annals.1419.028
175.
Michalski J. R. Cuadros J. Niles P. B. Parnell J. Deanne Rogers A. Wright S. P. (2013 ). Groundwater activity on Mars and implications for a deep biosphere. Nat. Geosci. 6 133–138.
Not in our library10.1038/ngeo1706
176.
Michalski J. R. Onstott T. C. Mojzsis S. J. Mustard J. Chan Q. H. S. Niles P. B. (2018 ). The Martian subsurface as a potential window into the origin of life. Nat. Geosci. 11:21
Not in our library10.1038/s41561-017-0015-2
177.
Michiels C. Bartlett D. H. Aersten A. (eds) (2008 ). High-Pressure Microbiology. Washington, DC: American Society of Microbiology
Not in our library10.1128/9781555815646
178.
Miettinen H. Kietäväinen R. Sohlberg E. Numminen M. Ahonen L. Itävaara M. (2015 ). Microbiome composition and geochemical characteristics of deep subsurface high-pressure environment, Pyhäsalmi mine Finland. Front. Microbiol. 6:1203
Not in our library10.3389/fmicb.2015.01203
179.
Mildrexler D. J. Zhao M. Running S. W. (2011 ). Satellite finds highest land skin temperatures on Earth. Bull. Am. Meteorol. Soc. 92 855–860.
Not in our library10.1175/2011bams3067.1
180.
Miller S. R. Strong A. L. Jones K. L. Ungerer M. C. (2009 ). Bar-coded pyrosequencing reveals shared bacterial community properties along the temperature gradients of two alkaline hot springs in Yellowstone National Park. Appl. Environ. Microbiol. 75 4565–4572.
Not in our library10.1128/aem.02792-08
181.
Millero F. J. Rabindra N. R. (1997 ). A chemical equilibrium model for the carbonate system in natural waters. Croat. Chem. Acta 70 1–38.
Not in our library
182.
Mitchell J. L. Lora J. M. (2016 ). The climate of titan. Annu. Rev. Earth Planet. Sci. 44 353–380.
Not in our library10.1146/annurev-earth-060115-012428
183.
Mitri G. Meriggiola R. Hayes A. Lefevre A. Tobie G. Genova A. (2014 ). Shape, topography, gravity anomalies and tidal deformation of Titan. Icarus 236 169–177.
Not in our library10.1016/j.icarus.2014.03.018
184.
Mitri G. Showman A. P. (2008 ). Thermal convection in ice-I shells of Titan and Enceladus. Icarus 193 387–396.
Not in our library10.1016/j.icarus.2007.07.016
185.
Mojib N. Farhoomand A. Andersen D. T. Bej A. K. (2013 ). UV and cold tolerance of a pigment-producing Antarctic Janthinobacterium sp, Ant5-2. Extremophiles 17 367–378.
Not in our library10.1007/s00792-013-0525-9
186.
Moore E. K. Jelen B. I. Giovannelli D. Raanan H. Falkowski P. G. (2017 ). Metal availability and the expanding network of microbial metabolisms in the Archaean eon. Nat. Geosci. 10 629–636.
Not in our library10.1038/ngeo3006
187.
Mormile M. R. Romine M. F. Garcia M. T. Ventosa A. Bailey T. J. Peyton B. M. (1999 ). Halomonas campisalis sp, nov., a denitrifying, moderately haloalkaliphilic bacterium. Syst. Appl. Microbiol. 22 551–558.
Not in our library10.1016/s0723-2020(99)80008-3
188.
Morris S. Taylor A. C. (1983 ). Diurnal and seasonal variation in physico-chemical conditions within intertidal rock pools. Estuar. Coast. Shelf Sci. 17 339–355.
Not in our library10.1016/0272-7714(83)90026-4
189.
Mottl M. J. Komor S. C. Fryer P. Moyer C. L. (2003 ). Deep-slab fluids fuel extremophilic Archaea on a Mariana forearc serpentinite mud volcano: ocean drilling program leg 195. Geochem. Geophys. Geosyst. 4:GC00588
Not in our library10.1029/2003gc000588
190.
Mottl M. J. Wheat C. G. Fryer P. Gharib J. Martin J. B. (2004 ). Chemistry of springs across the Mariana forearc shows progressive devolatilization of the subducting plate. Geochim. Cosmochim. Acta 68 4915–4933.
Not in our library10.1016/j.gca.2004.05.037
191.
Muñoz-Iglesias V. Bonales L. J. Prieto-Ballesteros O. (2013 ). pH and Salinity Evolution of Europa’s Brines: Raman Spectroscopy Study of Fractional Precipitation at 1 and 300 Bar. Astrobiology 13 693–702.
Not in our library10.1089/ast.2012.0900
192.
Mykytczuk N. C. S. Foote S. J. Omelon C. R. Southam G. Greer C. W. Whyte L. G. (2013 ). Bacterial growth at -15°C; molecular insights from the permafrost bacterium Planococcus halocryophilus Or1. ISME J. 7 1211–1226.
Not in our library10.1038/ismej.2013.8
193.
Mykytczuk N. C. S. Wilhelm R. C. Whyte L. G. (2012 ). Planococcus halocryophilus sp. nov., an extreme sub-zero species from high arctic permafrost. Int. J. Syst. Evol. Microbiol. 62 1937–1944.
Not in our library10.1099/ijs.0.035782-0
194.
Namsaraev Z. B. Gorlenko V. M. Namsaraev B. B. Buryukhaev S. P. Yurkov V. V. (2003 ). The structure and biogeochemical activity of the phototrophic communities from the bol’sherechenskii alkaline hot spring. Microbiology 72 193–202.
Not in our library10.1023/a:1023272131859
195.
NASA (2018 ). Mars Fact Sheet. Greenbelt, MD: NASA Available at: https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html (accessed September 27, 2018).
Not in our library
196.
Formation of H<sub>2 </sub>and CH<sub>4 </sub>by weathering of olivine at temperatures between 30 and 70°C · 2011
Not checked
197.
Nevarez L. Vasseur V. Le Madec A. Le Bras M. A. Coroller L. Leguérinel I. (2009 ). Physiological traits of Penicillium glabrum strain LCP 08.5568, a filamentous fungus isolated from bottled aromatised mineral water. Int. J. Food Microbiol. 130 166–171.
Not in our library10.1016/j.ijfoodmicro.2009.01.013
198.
Neveu M. Desch S. J. (2015 ). Geochemistry, thermal evolution, and cryovolcanism on Ceres with a muddy ice mantle. Geophys. Res. Lett. 42 10197–10206.
Not in our library10.1002/2015gl066375
199.
Nicholson W. L. Krivushin K. Gilichinsky D. Schuerger A. C. (2013 ). Growth of Carnobacterium spp. from permafrost under low pressure, temperature, and anoxic atmosphere has implications for Earth microbes on Mars. Proc. Natl. Acad. Sci. U.S.A. 110 666–671.
Not in our library10.1073/pnas.1209793110
200.
Nicholson W. L. Schuerger A. C. (2005 ). Bacillus subtilis spore survival and expression of germination-induced bioluminescence after prolonged incubation under simulated mars atmospheric pressure and composition: implications for planetary protection and Lithopanspermia. Astrobiology 5 536–544.
Not in our library10.1089/ast.2005.5.536
201.
Noack L. Höning D. Rivoldini A. Heistracher C. Zimov N. Journaux B. (2016 ). Water-rich planets: How habitable is a water layer deeper than on Earth? Icarus 277 215–236.
Not in our library10.1016/j.icarus.2016.05.009
202.
Noell A. C. Ely T. Bolser D. K. Darrach H. Hodyss R. Johnson P. V. (2015 ). Spectroscopy and Viability of Bacillus subtilis Spores after Ultraviolet Irradiation: Implications for the Detection of Potential Bacterial Life on Europa. Astrobiology 15 20–31.
Not in our library10.1089/ast.2014.1169
203.
Nogi Y. Hosoya S. Kato C. Horikoshi K. (2004 ). Colwellia piezophila sp. nov., a novel piezophilic species from deep-sea sediments of the Japan Trench. Int. J. Syst. Evol. Microbiol. 54 1627–1631.
Not in our library10.1099/ijs.0.03049-0
204.
Nordheim T. A. Hand K. P. Paranicas C. (2018 ). Preservation of potential biosignatures in the shallow subsurface of Europa. Nat. Astron. 2 673–679.
Not in our library10.1038/s41550-018-0499-8
205.
Nordstrom D. K. Alpers C. N. Ptacek C. J. Blowes D. W. (2000 ). Negative pH and extremely acidic mine waters from Iron Mountain, California. Environ. Sci. Technol. 34 254–258.
Not in our library10.1021/es990646v
206.
Nordstrom D. K. Ball J. W. Mccleskey R. B. (2005 ). “Ground water to surface water: chemistry of thermal outflows in Yellowstone National Park,” in Geothermal Biology and Geochemistry in Yellowstone National Park eds Inskeep W. McDermott T. R. (Bozeman, MT: Montana State University) 73–94.
Not in our library
207.
Norman L. H. (2011 ). Is there life on … Titan? Astron. Geophys. 52 39–31.
Not in our library10.1111/j.1468-4004.2011.52139.x
208.
Oger P. M. Jebbar M. (2010 ). The many ways of coping with pressure. Res. Microbiol. 161 799–809.
Not in our library10.1016/j.resmic.2010.09.017
209.
Ojha L. Wilhelm M. B. Murchie S. L. McEwen A. S. Wray J. J. Hanley J. (2015 ). Spectral evidence for hydrated salts in recurring slope lineae on Mars. Nat. Geosci. 8 829–832.
Not in our library10.1038/ngeo2546
210.
Olson G. J. Brierley J. A. Brierley C. L. (2003 ). Bioleaching review part B: progress in bioleaching: applications of microbial processes by the minerals industries. Appl. Microbiol. Biotechnol. 63 249–257.
Not in our library10.1007/s00253-003-1404-6
211.
Onofri S. Selbmann L. Pacelli C. de Vera J. Horneck G. Hallsworth J. (2018 ). Integrity of the DNA and Cellular Ultrastructure of Cryptoendolithic Fungi in Space or Mars Conditions: a 1.5-Year Study at the International Space Station. Life 8:23.
Not in our library10.3390/life8020023
212.
Oremland R. Kulp T. Blum J. Hoeft S. Baesman S. Miller L. (2005 ). A microbial arsenic cycle in a salt-saturated, extreme environment. Science 308 1305–1308.
Not in our library10.1126/science.1110832
213.
Oren A. (2011 ). Thermodynamic limits to microbial life at high salt concentrations. Environ. Microbiol. 13 1908–1923.
Not in our library10.1111/j.1462-2920.2010.02365.x
214.
Oren A. (2013 ). “Life in magnesium- and calcium-rich hypersaline environments: salt stress By Chaotropic Ions,” in Polyextremophiles. Cellular Origin, Life in Extreme Habitats and Astrobiology eds Seckbach J. Oren A. Stan-Lotter H. (Dordrecht: Springer) 215–232.
Not in our library10.1007/978-94-007-6488-0
215.
Pandit A. S. Joshi M. N. Bhargava P. Shaikh I. Ayachit G. N. Raj S. R. (2015 ). A snapshot of microbial communities from the Kutch: one of the largest salt deserts in the World. Extremophiles 19 973–987.
Not in our library10.1007/s00792-015-0772-z
216.
Pankova E. I. Konyushkova M. V. (2013 ). Climate and soil salinity in the deserts of Central Asia. Eurasian Soil Sci. 46 721–727.
Not in our library10.1134/s1064229313070065
217.
Pasek M. A. Greenberg R. (2012 ). Acidification of Europa’s Subsurface Ocean as a Consequence of Oxidant Delivery. Astrobiology 12 151–159.
Not in our library10.1089/ast.2011.0666
218.
Pavlov A. Cheptsov V. Tsurkov D. Lomasov V. Frolov D. Vasiliev G. (2018 ). Survival of Radioresistant Bacteria on Europa’s Surface after Pulse Ejection of Subsurface Ocean Water. Geosciences 9:9
Not in our library10.3390/geosciences9010009
219.
Phoenix V. R. Bennett P. C. Engel A. S. Tyler S. W. Ferris F. G. (2006 ). Chilean high-altitude hot-spring sinters: a model system for UV screening mechanisms by early Precambrian cyanobacteria. Geobiology 4 15–28.
Not in our library10.1111/j.1472-4669.2006.00063.x
220.
Picard A. Daniel I. (2013 ). Pressure as an environmental parameter for microbial life - A review. Biophys. Chem. 183 30–41.
Not in our library10.1016/j.bpc.2013.06.019
221.
Pikuta E. Lysenko A. Chuvilskaya N. Mendrock U. Hippe H. Suzina N. (2000 ). Anoxybacillus pushchinensis gen. nov., sp. nov., a novel anaerobic, alkaliphilic, moderately thermophilic bacterium from manure, and description of Anoxybacillus flavithermus comb. nov. Int. J. Syst. Evol. Microbiol. 50 2109–2117.
Not in our library10.1099/00207713-50-6-2109
222.
Plümper O. King H. E. Geisler T. Liu Y. Pabst S. Savov I. P. (2017 ). Subduction zone forearc serpentinites as incubators for deep microbial life. Proc. Natl. Acad. Sci. U.S.A. 114 4324–4329.
Not in our library10.1073/pnas.1612147114
223.
Microbial Diversity in a Hypersaline Sulfate Lake: A Terrestrial Analog of Ancient Mars · 2017
Not checked
224.
Postberg F. Kempf S. Schmidt J. Brilliantov N. Beinsen A. Abel B. (2009 ). Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus. Nature 459 1098–1101.
Not in our library10.1038/nature08046
225.
Postberg F. Khawaja N. Abel B. Choblet G. Glein C. R. Gudipati M. S. (2018 ). Macromolecular organic compounds from the depths of Enceladus. Nature 558 564–568.
Not in our library10.1038/s41586-018-0246-4
226.
Price P. B. Sowers T. (2004 ). Temperature dependence of metabolic rates for microbial growth, maintenance, and survival. Proc. Natl. Acad. Sci. U.S.A. 101 4631–4636.
Not in our library10.1073/pnas.0400522101
227.
Price R. E. Giovannelli D. (2017 ). “A review of the geochemistry and microbiology of marine shallow-water hydrothermal vents,” in Reference Module in Earth Systems and Environmental Sciences ed. Elias S. A. (Amsterdam: Elsevier).
Not in our library
228.
Prieto G. A. Froment B. Yu C. Poli P. Abercrombie R. (2017 ). Earthquake rupture below the brittle-ductile transition in continental lithospheric mantle. Sci. Adv. 3:e1602642.
Not in our library10.1126/sciadv.1602642
229.
Purcell D. Sompong U. Yim L. C. Barraclough T. G. Peerapornpisal Y. Pointing S. B. (2007 ). The effects of temperature, pH and sulphide on the community structure of hyperthermophilic streamers in hot springs of northern Thailand. FEMS Microbiol. Ecol. 60 456–466.
Not in our library10.1111/j.1574-6941.2007.00302.x
230.
Qi J. Xu M. An C. Wu M. Zhang Y. Li X. (2017 ). Characterizations of geothermal springs along the Moxi deep fault in the western Sichuan plateau, China. Phys. Earth Planet. Inter. 263 12–22.
Not in our library10.1016/j.pepi.2017.01.001
231.
Quehenberger J. Shen L. Albers S. V. Siebers B. Spadiut O. (2017 ). Sulfolobus - A potential key organism in future biotechnology. Front. Microbiol. 8:2474.
Not in our library10.3389/fmicb.2017.02474
232.
Rainey F. A. Ray K. Ferreira M. Gatz B. Z. Nobre M. F. Bagaley D. (2005 ). Extensive diversity of ionizing-radiation-resistant bacteria recovered from Sonoran Desert soil and description of nine new species of the genus Deinococcus obtained from a single soil sample. Appl. Environ. Microbiol. 71 5225–5235.
Not in our library10.1128/aem.71.9.5225-5235.2005
233.
Reid I. N. Sparks W. B. Lubow S. McGrath M. Livio M. Valenti J. (2006 ). Terrestrial models for extraterrestrial life: methanogens and halophiles at Martian temperatures. Int. J. Astrobiol. 5 89–97.
Not in our library10.1017/s1473550406002916
234.
Resing J. A. Baker E. T. Lupton J. E. Embley R. W. Massoth G. J. Chadwick J. W. (2007 ). Venting of acid-sulfate fluids in a high-sulfidation setting at NW Rota-1 submarine volcano on the Mariana Arc. Econ. Geol. 102 1047–1061.
Not in our library10.2113/gsecongeo.102.6.1047
235.
Rivkina E. M. Friedmann E. I. McKay C. P. Gilichinsky D. A. (2000 ). Metabolic activity of Permafrost Bacteria below the freezing point. Appl. Environ. Microbiol. 66 3230–3233.
Not in our library10.1128/aem.66.8.3230-3233.2000
236.
Roadcap G. S. Sanford R. A. Jin Q. Pardinas J. R. Bethke C. M. (2006 ). Extremely alkaline (pH > 12) ground water hosts diverse microbial community. Ground Water 44 511–517.
Not in our library10.1111/j.1745-6584.2006.00199.x
237.
Rohwerder T. Gehrke T. Kinzler K. Sand W. (2003 ). Bioleaching review part A: progress in bioleaching: fundamentals and mechanisms of bacterial metal sulfide oxidation. Appl. Microbiol. Biotechnol. 63 239–248.
Not in our library10.1007/s00253-003-1448-7
238.
Rosso L. Lobry J. R. Bajard S. Flandrois J. P. (1995 ). Convenient model to describe the combined effects of temperature and pH on microbial growth. Appl. Environ. Microbiol. 61 610–616.
Not in our library10.1128/aem.61.2.610-616.1995
239.
Rothschild L. J. Mancinelli R. L. (2001 ). Life in extreme environments. Nature 409 1092–1101.
Not in our library10.1038/35059215
240.
Rousk J. Bååth E. Brookes P. C. Lauber C. L. Lozupone C. Caporaso J. G. (2010 ). Soil bacterial and fungal communities across a pH gradient in an arable soil. ISME J. 4 1340–1351.
Not in our library10.1038/ismej.2010.58
241.
Russell M. J. Barge L. M. Bhartia R. Bocanegra D. Bracher P. J. Branscomb E. (2014 ). The drive to life on wet and icy worlds. Astrobiology 14 308–343.
Not in our library10.1089/ast.2013.1110
242.
Russell M. J. Hall A. J. Martin W. (2010 ). Serpentinization as a source of energy at the origin of life. Geobiology 8 355–371.
Not in our library10.1111/j.1472-4669.2010.00249.x
243.
Russell M. J. Murray A. E. Hand K. P. (2017 ). The possible emergence of life and differentiation of a shallow biosphere on irradiated icy worlds: the example of Europa. Astrobiology 17 1265–1273.
Not in our library10.1089/ast.2016.1600
244.
Samarkin V. A. Madigan M. T. Bowles M. W. Casciotti K. L. Priscu J. C. McKay C. P. (2010 ). Abiotic nitrous oxide emission from the hypersaline Don Juan Pond in Antarctica. Nat. Geosci. 3 341–344.
Not in our library10.1038/ngeo847
245.
Scambelluri M. Piccardo G. Philippot P. Robbiano A. Negretti L. (1997 ). High salinity fluid inclusions formed from recycled seawater in deeply subducted alpine serpentinite. Earth Planet. Sci. Lett. 148 485–499.
Not in our library10.1016/s0012-821x(97)00043-5
246.
Scambos T. A. Campbell G. G. Pope A. Haran T. Muto A. Lazzara M. (2018 ). Ultralow surface temperatures in East Antarctica from satellite thermal infrared mapping: the coldest places on earth. Geophys. Res. Lett. 45 6124–6133.
Not in our library10.1029/2018gl078133
247.
Schleper C. Puehler G. Holz I. Gambacorta A. Janekovic D. Santarius U. (1995 ). Picrophilus gen. nov., fam. nov.: a novel aerobic, heterotrophic, thermoacidophilic genus and family comprising archaea capable of growth around pH 0. J. Bacteriol. 177 7050–7059.
Not in our library10.1128/jb.177.24.7050-7059.1995
248.
Schleper C. Puhler G. Klenk H.-P. Zillig W. (1996 ). Picrophilus oshimae and Picrophilus torridus fam. nov., gen. nov., sp. nov., two species of hyperacidophilic, thermophilic, heterotrophic, aerobic archaea. Int. J. 46 814–816.
Not in our library10.1099/00207713-46-3-814
249.
Schrenk M. O. Brazelton W. J. Lang S. Q. (2013 ). Serpentinization, carbon, and deep life. Rev. Mineral. Geochem. 75 575–606.
Not in our library10.2138/rmg.2013.75.18
250.
Schrenk M. O. Edwards K. J. Goodman R. M. Hamers R. J. Banfield J. F. (1998 ). Distribution of Thiobacillus ferrooxidans and Leptospirillum ferrooxidans: implications for generation of acid mine drainage. Science 279 1519–1522.
Not in our library10.1126/science.279.5356.1519
251.
Schuerger A. C. Mancinelli R. L. Kern R. G. Rothschild L. J. McKay C. P. (2003 ). Survival of endospores of Bacillus subtilis on spacecraft surfaces under simulated martian environments: implications for the forward contamination of Mars. Icarus 165 253–276.
Not in our library10.1016/s0019-1035(03)00200-8
252.
Schuerger A. C. Nicholson W. L. (2016 ). Twenty species of hypobarophilic bacteria recovered from diverse soils exhibit growth under simulated Martian conditions at 0.7kPa. Astrobiology 16 964–976.
Not in our library10.1089/ast.2016.1587
253.
Schulze-Makuch D. (2013 ). “Extremophiles on alien worlds: what types of organismic adaptations are feasible on other planetary bodies,” in Habitability of Other Planets and Satellites eds de Vera J.-P. Seckbach J. (Berlin: Springer) 253–265.
Not in our library10.1007/978-94-007-6546-7_14
254.
The Adaptability of Life on Earth and the Diversity of Planetary Habitats · 2017
Not checked
255.
Schulze-Makuch D. Grinspoon D. H. Abbas O. Irwin L. N. Bullock M. A. (2004 ). A sulfur-based survival strategy for putative phototrophic life in the venusian atmosphere. Astrobiology 4 11–18.
Not in our library10.1089/153110704773600203
256.
Schwieterman E. W. Kiang N. Y. Parenteau M. N. Harman C. E. DasSarma S. Fisher T. M. (2018 ). Exoplanet biosignatures: a review of remotely detectable signs of life. Astrobiology 18 663–708.
Not in our library10.1089/ast.2017.1729
257.
Seager S. (2013 ). Exoplanet habitability. Science 340 577–581.
Not in our library10.1126/science.1232226
258.
Seckbach J. Oren A. Stan-Lotter H. (eds) (2013 ). Polyextremophiles. Dordrecht: Springer
Not in our library10.1007/978-94-007-6488-0
259.
Segerer A. Neuner A. Kristjansson J. K. Stetter K. O. (1986 ). Acidianus infernus gen. nov., sp. nov., and Acidianus brierleyi Comb. nov.: facultatively aerobic, extremely acidophilic thermophilic sulfur-metabolizing archaebacteria. Int. J. Syst. Bacteriol. 36 559–564.
Not in our library10.1099/00207713-36-4-559
260.
Sghaier H. Thorvaldsen S. Saied N. M. (2013 ). There are more small amino acids and fewer aromatic rings in proteins of ionizing radiation-resistant bacteria. Ann. Microbiol. 63 1483–1491.
Not in our library10.1007/s13213-013-0612-2
261.
Sharma A. Scott J. H. Cody G. D. Fogel M. L. Hazen R. M. Hemley R. J. (2002 ). Microbial activity at gigapascal pressures. Science 295 1514–1516.
Not in our library10.1126/science.1068018
262.
Sharp C. E. Brady A. L. Sharp G. H. Grasby S. E. Stott M. B. Dunfield P. F. (2014 ). Humboldt’s spa: microbial diversity is controlled by temperature in geothermal environments. ISME J. 8 1166–1174.
Not in our library10.1038/ismej.2013.237
263.
Shock E. L. Boyd E. S. (2015 ). Principles of geobiochemistry. Elements 11 395–401.
Not in our library10.2113/gselements.11.6.395
264.
Siegert M. J. Ellis-Evans J. C. Tranter M. Mayer C. Petit J. R. Salamatin A. (2001 ). Physical, chemical and biological processes in Lake Vostok and other Antarctic subglacial lakes. Nature 414 603–609.
Not in our library10.1038/414603a
265.
Singh D. Takahashi K. Kim M. Chun J. Adams J. M. (2012 ). A Hump-backed trend in bacterial diversity with elevation on Mount Fuji, Japan. Microb. Ecol. 63 429–437.
Not in our library10.1007/s00248-011-9900-1
266.
Sinha N. Nepal S. Kral T. Kumar P. (2017 ). Survivability and growth kinetics of methanogenic archaea at various pHs and pressures: implications for deep subsurface life on Mars. Planet. Space Sci. 136 15–24.
Not in our library10.1016/j.pss.2016.11.012
267.
Smith D. J. Schuerger A. C. Davidson M. M. Pacala S. W. Bakermans C. Onstott T. C. (2009 ). Survivability of Psychrobacter cryohalolentis K5 under simulated martian surface conditions. Astrobiology 9 221–228.
Not in our library10.1089/ast.2007.0231
268.
Soderlund K. M. Schmidt B. E. Wicht J. Blankenship D. D. (2014 ). Ocean-driven heating of Europa’s icy shell at low latitudes. Nat. Geosci. 7 16–19.
Not in our library10.1038/ngeo2021
269.
Sohl F. Solomonidou A. Wagner F. W. Coustenis A. Hussmann H. Schulze-Makuch D. (2014 ). Structural and tidal models of Titan and inferences on cryovolcanism. J. Geophys. Res. Planets 119 1013–1036.
Not in our library10.1002/2013je004512
270.
Spencer J. R. Tamppari L. K. Martin T. Z. Travis L. D. (1999 ). Temperatures on Europa from Galileo photopolarimeter-radiometer: nighttime thermal anomalies. Science 284 1514–1516.
Not in our library10.1126/science.284.5419.1514
271.
Steinle L. Knittel K. Felber N. Casalino C. De Lange G. Tessarolo C. (2018 ). Life on the edge: active microbial communities in the Kryos MgCl2-brine basin at very low water activity. ISME J. 12 1414–1426.
Not in our library10.1038/s41396-018-0107-z
272.
Stetter K. O. (1982 ). Ultrathin mycelia-forming organisms from submarine volcanic areas having an optimum growth temperature of 105°C. Nature 300 258–260.
Not in our library10.1038/300258a0
273.
Is there a common water-activity limit for the three domains of life? · 2014
No notice
274.
Suzuki S. Ishii S. Wu A. Cheung A. Tenney A. Wanger G. (2013 ). Microbial diversity in The Cedars, an ultrabasic, ultrareducing, and low salinity serpentinizing ecosystem. Proc. Natl. Acad. Sci. U.S.A. 110 15336–15341.
Not in our library10.1073/pnas.1302426110
275.
Suzuki S. Kuenen J. G. Schipper K. Van Der Velde S. Ishii S. Wu A. (2014 ). Physiological and genomic features of highly alkaliphilic hydrogen-utilizing Betaproteobacteria from a continental serpentinizing site. Nat. Commun. 5:3900.
Not in our library10.1038/ncomms4900
276.
Swan B. K. Ehrhardt C. J. Reifel K. M. Moreno L. I. Valentine D. L. (2010 ). Archaeal and bacterial communities respond differently to environmental gradients in anoxic sediments of a California hypersaline lake, the Salton Sea. Appl. Environ. Microbiol. 76 757–768.
Not in our library10.1128/aem.02409-09
277.
Takai K. Nakamura K. Toki T. Tsunogai U. Miyazaki M. Miyazaki J. (2008 ). Cell proliferation at 122 C and isotopically heavy CH4 production by a hyperthermophilic methanogen under high-pressure cultivation. Proc. Natl. Acad. Sci. U.S.A. 105 10949–10954.
Not in our library10.1073/pnas.0712334105
278.
Tambekar D. H. Pawar A. L. Dudhane M. N. (2010 ). Lonar lake water: past and present. Nat. Envion. Pollut. Tech. 9 217–221.
Not in our library
279.
Taran Y. A. (2009 ). Geochemistry of volcanic and hydrothermal fluids and volatile budget of the Kamchatka-Kuril subduction zone. Geochim. Cosmochim. Acta 73 1067–1094.
Not in our library10.1016/j.gca.2008.11.020
280.
Biological methane production under putative Enceladus-like conditions · 2018
Not checked
281.
Teolis B. D. Wyrick D. Y. Bouquet A. Magee B. A. Waite J. H. (2017 ). Plume and surface feature structure and compositional effects on Europa’s global exosphere: preliminary Europa mission predictions. Icarus 284 18–29.
Not in our library10.1016/j.icarus.2016.10.027
282.
Toner J. D. Catling D. C. Sletten R. S. (2017 ). The geochemistry of Don Juan Pond: evidence for a deep groundwater flow system in Wright Valley Antarctica. Earth Planet. Sci. Lett. 474 190–197.
Not in our library10.1016/j.epsl.2017.06.039
283.
Torii T. Murata S. Yamagata N. (1981 ). Geochemistry of the Dry Valley lakes. J. R. Soc. New Zeal. 11 387–399. 25674080
Not in our library10.1080/03036758.1981.10423329
284.
Trapeznikov A. (1983 ). Radioactivity in the Canadian environment. Natl. Res. Counc. Canada 19250:292.
Not in our library
285.
Travis B. J. Palguta J. Schubert G. (2012 ). A whole-moon thermal history model of Europa: impact of hydrothermal circulation and salt transport. Icarus 218 1006–1019.
Not in our library10.1016/j.icarus.2012.02.008
286.
Tutu H. McCarthy T. S. Cukrowska E. (2008 ). The chemical characteristics of acid mine drainage with particular reference to sources, distribution and remediation: the Witwatersrand Basin, South Africa as a case study. Appl. Geochem. 23 3666–3684.
Not in our library10.1016/j.apgeochem.2008.09.002
287.
Van Der Wielen P. W. J. J. Bolhuis H. Borin S. Daffonchio D. Corselli C. Giuliano L. (2005 ). The enigma of prokaryotic life in deep hypersaline anoxic basins. Science 307 121–123.
Not in our library10.1126/science.1103569
288.
Van Dover C. L. Humphris S. E. Fornari D. Cavanaugh C. M. Collier R. Goffredi S. K. (2001 ). Biogeography and ecological setting of Indian Ocean hydrothermal vents. Science 294 818–823.
Not in our library10.1126/science.1064574
289.
Vance S. D. Hand K. P. Pappalardo R. T. (2016 ). Geophysical controls of chemical disequilibria in Europa. Geophys. Res. Lett. 43 4871–4879.
Not in our library10.1002/2016gl068547.received
290.
Vanlint D. Mitchell R. Bailey E. Meersman F. McMillan P. F. Michiels C. W. (2011 ). Rapid acquisition of gigapascal-high-pressure resistance by Escherichia coli. mBio 2:e00130-10.
Not in our library10.1128/mbio.00130-10
291.
Varnes E. S. Jakosky B. M. McCollom T. M. (2003 ). Biological potential of Martian hydrothermal systems. Astrobiology 3 407–414.
Not in our library10.1089/153110703769016479
292.
Villarreal M. N. Russell C. T. Luhmann J. G. Thompson W. T. Prettyman T. H. A’Hearn M. F. (2017 ). The dependence of the cerean exosphere on solar energetic particle events. Astrophys. J. 838:L8
Not in our library10.3847/2041-8213/aa66cd
293.
Vu T. H. Hodyss R. Johnson P. V. Choukroun M. (2017 ). Preferential formation of sodium salts from frozen sodium-ammonium-chloride-carbonate brines – Implications for Ceres’ bright spots. Planet. Space Sci. 141 73–77.
Not in our library10.1016/j.pss.2017.04.014
294.
Waite J. H. Lewis W. S. Magee B. A. Lunine J. I. McKinnon W. B. Glein C. R. (2009 ). Liquid water on Enceladus from observations of ammonia and40Ar in the plume. Nature 460 487–490.
Not in our library10.1038/nature08153
295.
Waldron P. J. Petsch S. T. Martini A. M. Nüslein K. (2007 ). Salinity constraints on subsurface archaeal diversity and methanogenesis in sedimentary rock rich in organic matter. Appl. Environ. Microbiol. 73 4171–4179.
Not in our library10.1128/aem.02810-06
296.
Walsh E. A. Kirkpatrick J. B. Rutherford S. D. Smith D. C. Sogin M. D’Hondt S. (2016 ). Bacterial diversity and community composition from seasurface to subseafloor. ISME J. 10 979–989.
Not in our library10.1038/ismej.2015.175
297.
Wayne R. P. (2000 ). Chemistry of Atmospheres 3rd Edn. Oxford: Clarendon Press.
Not in our library
298.
Webb K. M. DiRuggiero J. (2013 ). “Radiation resistance in extremophiles: fending off multiple attacks,” in Polyextremophiles: Life Under Multiple Forms of Stress eds Seckbach J. Oren A. Stan-Lotter H. (Dordrecht: Springer) 249–267.
Not in our library10.1007/978-94-007-6488-0_10
299.
Weiss B. P. Fong L. E. Vali H. Lima E. A. Baudenbacher F. J. (2008 ). Paleointensity of the ancient Martian magnetic field. Geophys. Res. Lett. 35:L23207
Not in our library10.1029/2008gl035585
300.
Wheeler K. A. Hurdman B. F. Pitt J. I. (1991 ). Influence of pH on the growth of some toxigenic species of Aspergillus, Penicillium and Fusarium. Int. J. Food Microbiol. 12 141–149.
Not in our library10.1016/0168-1605(91)90063-u
301.
Wordsworth R. (2016 ). The climate of early mars. Annu. Rev. Earth Planet. Sci. 44 381–408.
Not in our library10.1146/annurev-earth-060115-012355
302.
Xiao X. Wang P. Zeng X. Bartlett D. H. Wang F. (2007 ). Shewanella psychrophila sp. nov. and Shewanella piezotolerans sp. nov., isolated from west Pacific deep-sea sediment. Int. J. Syst. Evol. Microbiol. 57 60–65.
Not in our library10.1099/ijs.0.64500-0
303.
Geographic distance and pH drive bacterial distribution in alkaline lake sediments across Tibetan Plateau · 2012
No notice
304.
Yakimov M. M. La Cono V. Slepak V. Z. La Spada G. Arcadi E. Messina E. (2013 ). Microbial life in the Lake Medee, the largest deep-sea salt-saturated formation. Sci. Rep. 3:3554.
Not in our library10.1016/0301-0104(89)87026-0
305.
Yakimov M. M. La Cono V. Spada G. L. Bortoluzzi G. Messina E. Smedile F. (2015 ). Microbial community of the deep-sea brine Lake Kryos seawater-brine interface is active below the chaotropicity limit of life as revealed by recovery of mRNA. Environ. Microbiol. 17 364–382.
Not in our library10.1111/1462-2920.12587
306.
Yamagishi A. Kawaguchi Y. Hashimoto H. Yano H. Imai E. Kodaira S. (2018 ). Environmental data and survival data of Deinococcus aetherius from the exposure facility of the Japan experimental module of the international space station obtained by the tanpopo mission. Astrobiology 18 1369–1374.
Not in our library10.1089/ast.2017.1751
307.
Salinity shapes microbial diversity and community structure in surface sediments of the Qinghai-Tibetan Lakes · 2016
No notice
308.
Yayanos A. A. Dietz A. S. Van Boxtel R. (1981 ). Obligately barophilic bacterium from the Mariana trench. Proc. Natl. Acad. Sci. U.S.A. 78 5212–5215.
Not in our library10.1073/pnas.78.8.5212
309.
Zhalnina K. Dias R. de Quadros P. D. Davis-Richardson A. Camargo F. A. O. Clark I. M. (2014 ). Soil pH determines microbial diversity and composition in the park grass experiment. Microb. Ecol. 69 395–406.
Not in our library10.1007/s00248-014-0530-2
310.
Zhang L. Su F. Kong X. Lee F. Day K. Gao W. (2016 ). Ratiometric fluorescent pH-sensitive polymers for high-throughput monitoring of extracellular pH. RSC Adv. 6 46134–46142.
Not in our library10.1039/c6ra06468j
311.
Zhou Z. Jiang F. Wang S. Peng F. Dai J. Li W. (2012 ). Pedobacter arcticus sp. nov., a facultative psychrophile isolated from Arctic soil, and emended descriptions of the genus Pedobacter, Pedobacter heparinus, Pedobacter daechungensis, Pedobacter terricola, Pedobacter glucosidilyticus and Pedobacter lentus. Int. J. Syst. Evol. Microbiol. 62 1963–1969.
Not in our library10.1099/ijs.0.031104-0
312.
Zhu P. Manucharyan G. E. Thompson A. F. Goodman J. C. Vance S. D. (2017 ). The influence of meridional ice transport on Europa’s ocean stratification and heat content. Geophys. Res. Lett. 44 5969–5977.
Not in our library10.1002/2017gl072996
313.
Zolotov M. Y. (2009 ). On the composition and differentiation of Ceres. Icarus 204 183–193.
Not in our library10.1016/j.icarus.2009.06.011
314.
Zolotov M. Y. (2017 ). Aqueous origins of bright salt deposits on Ceres. Icarus 296 289–304.
Not in our library10.1016/j.icarus.2017.06.018
315.
Zolotov M. Y. Kargel J. S. (2009 ). “On the chemical composition of Europa’s icy shell, ocean, and underlying rocks,” in Europa eds Pappalardo R. T. McKinnon W. B. Khurana K. (Tucson, AZ: University of Arizona Press) 431.
Not in our library
316.
Zolotov M. Y. Tobie G. Postberg F. Magee B. Waite J. H. Esposito L. (2011 ). Chemical and phase composition of Enceladus: insights from Cassini data. EPSC Abstracts 6:EPSC-DPS2011-1330
Not in our library10.1029/2011gl047415

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DNA Damage Protection for Enhanced Bacterial Survival Under Simulated Low Earth Orbit Environmental Conditions in Escherichia coli · 2021
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