Halophiles: A Terrestrial Analog for Life in Brines on Mars

Mancinelli, Rocco L.

doi:10.1007/1-4020-3633-7_10

Cited by 4 publications

(2 citation statements)

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“…Dispersal mechanisms of viable microbes away from landed or crashed spacecraft on Mars have not been adequately studied and remain significant black boxes in any Mars microbial survival and proliferation model. Long-term survival on Mars is unlikely if microbes are directly exposed to solar UV irradiation (11,37,47,49,50) but likely if the microbes are protected from UV irradiation by thin dust layers or embedded within UV-protected niches in spacecraft (33,39,47). In contrast, the greatest unknown in any Mars microbial survival and proliferation model is whether terrestrial microorganisms found on spacecraft are capable of growth and replication under Mars conditions.…”

Section: Discussionmentioning

confidence: 99%

“…Although controversial, halotolerant bacteria have been isolated from inclusions within 250-million-year-old salt crystals (58). While this is an extreme example of bacterial survival within inclusions, microbes commonly become entrapped within salt crystals (2,33). Though salts may aid cells in survival against desiccation or growth at subzero temperatures, there is a balance between these benefits and the cost of high osmolarity on cell survival, metabolism, and replication.…”

Section: Discussionmentioning

confidence: 99%

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Effects of Simulated Mars Conditions on the Survival and Growth of Escherichia coli and Serratia liquefaciens

Berry

Jenkins

Schuerger

2010

Appl Environ Microbiol

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Escherichia coli and Serratia liquefaciens, two bacterial spacecraft contaminants known to replicate under low atmospheric pressures of 2.5 kPa, were tested for growth and survival under simulated Mars conditions. Environmental stresses of high salinity, low temperature, and low pressure were screened alone and in combination for effects on bacterial survival and replication, and then cells were tested in Mars analog soils under simulated Mars conditions. Survival and replication of E. coli and S. liquefaciens cells in liquid medium were evaluated for 7 days under low temperatures (5, 10, 20, or 30°C) with increasing concentrations (0, 5, 10, or 20%) of three salts (MgCl 2 , MgSO 4 , NaCl) reported to be present on the surface of Mars. Moderate to high growth rates were observed for E. coli and S. liquefaciens at 30 or 20°C and in solutions with 0 or 5% salts. In contrast, cell densities of both species generally did not increase above initial inoculum levels under the highest salt concentrations (10 and 20%) and the four temperatures tested, with the exception that moderately higher cell densities were observed for both species at 10% MgSO 4 maintained at 20 or 30°C. Growth rates of E. coli and S. liquefaciens in low salt concentrations were robust under all pressures (2.5, 10, or 101.3 kPa), exhibiting a general increase of up to 2.5 orders of magnitude above the initial inoculum levels of the assays. Vegetative E. coli cells were maintained in a Mars analog soil for 7 days under simulated Mars conditions that included temperatures between 20 and ؊50°C for a day/night diurnal period, UVC irradiation (200 to 280 nm) at 3.6 W m ؊2 for daytime operations (8 h), pressures held at a constant 0.71 kPa, and a gas composition that included the top five gases found in the martian atmosphere. Cell densities of E. coli failed to increase under simulated Mars conditions, and survival was reduced 1 to 2 orders of magnitude by the interactive effects of desiccation, UV irradiation, high salinity, and low pressure (in decreasing order of importance). Results suggest that E. coli may be able to survive, but not grow, in surficial soils on Mars.The search for extant life on Mars remains a stated goal of NASA's Mars Exploration Program and Astrobiology Institutes (13,17). Intrinsic within such a life detection strategy is a requirement to understand how terrestrial life might survive, replicate, and proliferate on Mars. To mitigate the risks of the forward contamination of Mars, the bioloads on spacecrafts targeted for landing must be reduced to low density and diversity (4, 7). Planetary protection guidelines are designed to prevent both the forward contamination of the martian surface and to ensure the scientific integrity of any deployed life detection experiments. To date, 12 spacecraft have landed or crashed onto the Mars surface as a result of U.S., Russian, and European space program missions, but it is currently unknown if terrestrial microorganisms typically found on spacecraft surfaces can grow and replicate under con...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Effects of Simulated Mars Conditions on the Survival and Growth of Escherichia coli and Serratia liquefaciens

Berry

Jenkins

Schuerger

2010

Appl Environ Microbiol

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Terrestrial Martian Analog Heritage of Kachchh Basin, Western India

et al. 2022

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The affect of the space environment on the survival ofHalorubrum chaoviatorandSynechococcus(Nägeli): data from the Space Experiment OSMO on EXPOSE-R

Mancinelli

2014

International Journal of Astrobiology

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We have shown using ESA's Biopan facility flown in Earth orbit that when exposed to the space environment for 2 weeks the survival rate of Synechococcus (Nägeli), a halophilic cyanobacterium isolated from the evaporitic gypsum-halite crusts that form along the marine intertidal, and Halorubrum chaoviator a member of the Halobacteriaceae isolated from an evaporitic NaCl crystal obtained from a salt evaporation pond, were higher than all other test organisms except Bacillus spores. These results led to the EXPOSE-R mission to extend and refine these experiments as part of the experimental package for the external platform space exposure facility on the ISS. The experiment was flown in February 2009 and the organisms were exposed to low-Earth orbit for nearly 2 years. Samples were either exposed to solar ultraviolet (UV)-radiation (λ > 110 nm or λ > 200 nm, cosmic radiation (dosage range 225-320 mGy), or kept in darkness shielded from solar UV-radiation. Half of each of the UV-radiation exposed samples and dark samples were exposed to space vacuum and half kept at 10 5 pascals in argon. Duplicate samples were kept in the laboratory to serve as unexposed controls. Ground simulation control experiments were also performed. After retrieval, organism viability was tested using Molecular Probes Live-Dead Bac-Lite stain and by their reproduction capability. Samples kept in the dark, but exposed to space vacuum had a 90 ± 5% survival rate compared to the ground controls. Samples exposed to full UV-radiation for over a year were bleached and although results from Molecular Probes Live-Dead stain suggested *10% survival, the data indicate that no survival was detected using cell growth and division using the most probable number method. Those samples exposed to attenuated UV-radiation exhibited limited survival. Results from of this study are relevant to understanding adaptation and evolution of life, the future of life beyond earth, the potential for interplanetary transfer of viable microbes via meteorites and dust particles as well as spacecraft, and the physiology of halophiles.

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Halophiles: A Terrestrial Analog for Life in Brines on Mars

Cited by 4 publications

References 40 publications

Effects of Simulated Mars Conditions on the Survival and Growth of Escherichia coli and Serratia liquefaciens

Effects of Simulated Mars Conditions on the Survival and Growth of Escherichia coli and Serratia liquefaciens

Terrestrial Martian Analog Heritage of Kachchh Basin, Western India

The affect of the space environment on the survival ofHalorubrum chaoviatorandSynechococcus(Nägeli): data from the Space Experiment OSMO on EXPOSE-R

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