Abstract
On Mars, significant amounts (0.4–0.6%) of perchlorate ions were detected in dry soil by the Phoenix Wet Chemistry Laboratory and later confirmed with the Mars Science Laboratory. Therefore, the ability of Hydrogenothermus marinus, a desiccation tolerant bacterium, to survive and grow in the presence of perchlorates was determined. Results indicated that H. marinus was able to tolerate concentrations of sodium perchlorate up to 200 mM ( 1.6%) during cultivation without any changes in its growth pattern. After the addition of up to 440 mM ( 3.7%) sodium perchlorate, H. marinus showed significant changes in cell morphology; from single motile short rods to long cell chains up to 80 cells. Furthermore, it was shown that the known desiccation tolerance of H. marinus is highly influenced by a pre-treatment with different perchlorates; additive effects of desiccation and perchlorate treatments are visible in a reduced survival rate. These data demonstrate that thermophiles, especially H. marinus, have so far, unknown high tolerances against cell damaging treatments and may serve as model organisms for future space experiments.
Highlights
Research on perchlorates has increased over the course of the last 30 years
Halophilic Archaea and Bacteria (e.g., Halobacterium salinarum; Halomonas elongata) are able to grow to some extent in perchlorate containing medium up to 0.4 M Na-perchlorate (Oren et al, 2014; Matsubara et al, 2017)
H. marinus was as tolerant as the halophilic strains to perchlorates and could grow in the presence of 0.45 M Na-perchlorate
Summary
The natural occurrence of perchlorates is in geographically limited very arid environments such as the Atacama Desert in Chile (Trumpolt et al, 2005; Catling et al, 2010). Perchlorate concentrations in nitrate mineral deposits in the Atacama Desert are known to be 0.028 wt % (Michalski et al, 2004). On Earth, and on our neighboring planet Mars, perchlorates have been detected, in much higher concentrations than on Earth. Significant amounts of perchlorate ions (0.4–0.6%) were first detected by the Phoenix lander in regolith in the northern polar region (Vastitas Borealis) (Hecht et al, 2009). Data from the Compact Reconnaissance Imaging Spectrometer on board the Mars Reconnaissance Orbiter detected a mixture of sodium perchlorate (Na-perchlorate) and Mg-perchlorate in the Palikir and Hale crater (Ojha et al, 2015), at Horowitz
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