Salt Tolerance and UV Protection of Bacillus subtilis and Enterococcus faecalis under Simulated Martian Conditions

Godin Paul J.; Schuerger Andrew C.; Moores John E.

摘要

Ultraviolet (UV) irradiation on the surface of Mars is an important factor that affects the survivability of microorganisms on Mars. The possibility of martian brines made from Fe-2(SO4)(3), MnSO4, and MgSO4 salts providing a habitable niche on Mars via attenuation of UV radiation was investigated on the bacteria Bacillus subtilis and Enterococcus faecalis. Results demonstrate that it is possible for brines containing Fe-2(SO4)(3) on Mars to provide protection from harmful UV irradiation, even at concentrations as low as 0.5%. Brines made from MnSO4 and MgSO4 did not provide significant UV protection, and most spores/cells died over the course of short-term experiments. However, Fe-2(SO4)(3) brines are strongly acidic and thus were lethal to E. faecalis, when cells were exposed for 7 days. In contrast, B. subtilis, a spore-forming bacterium resistant to pH extremes, was unaffected by the acidic conditions of the brines and did not experience any significant lethal effects in Fe-2(SO4)(3). Any extant microbial life in martian Fe-2(SO4)(3) brines (if present) would need to be capable of surviving acidic environments, if these brines are to be considered a possible habitable niche. The results from this work are important to the search for life on planets with atmospheres that do not significantly attenuate UV radiation (i.e., like Mars) and to planetary protection, since it is possible that terrestrial bacteria in the genus Bacillus are likely to survive in Fe-sulfate brines on Mars.

机译：MARS表面上的紫外（UV）辐照是影响MARS上微生物活性的重要因素。在细菌芽孢杆菌和肠球菌粪便中，研究了由Fe-2（SO4）（3），MnSO4，MgSO4和MgSO4盐制成的Martian Brine的可能性在MARS上，在芽孢杆菌和肠球菌粪便中，在MARS上为MARS提供了可居住的利基。结果表明，含有Fe-2（SO4）（3）的盐水可以在MARS上提供免受有害的紫外线照射的保护，即使浓度低至0.5％。由MnSO4和MgSO4制成的盐水没有提供显着的UV保护，大多数孢子/细胞在短期实验过程中死亡。然而，Fe-2（SO4）（3）盐水是强烈酸性的，因此当细胞暴露7天时，粪便致死。相比之下，B.枯草芽孢杆菌，抗磷酸盐对磷酸盐抗极端抗性，不受盐酸酸性条件的影响，并且在Fe-2（SO 4）（3）中没有经历任何显着的致命作用。如果这些盐水被认为是可能的居住的利基，则需要在Martian Fe-2（SO4）（3）盐水（如果存在）中的任何现存的微生物寿命都需要能够存活酸性环境。这项工作的结果对于在具有大气的行星上寻找生命，这些行星不会显着衰减紫外线辐射（即火星）和行星保护，因为芽孢杆菌属的陆地细菌可能会存活火星上的Fe-硫酸盐水。

Salt Tolerance and UV Protection of Bacillus subtilis and Enterococcus faecalis under Simulated Martian Conditions

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