We present the hypothesis that microorganisms can change the freezing/melting curve of cold salty solutions by protein expression, as it is known that proteins can affect the liquid-to-ice transition, an ability that could be of ecological advantage for organisms on Earth and on Mars. We tested our hypothesis by identifying a suitable candidate, the well-known psycrophile and halotolerant bacteria Rhodococcus sp. JG3, and analyzing its response in culture conditions that included specific hygroscopic salts relevant to Mars—that is, highly concentrated magnesium perchlorate solutions of 20 wt % and 50 wt % Mg(ClO₄)₂ at both end members of the eutectic concentration (44 wt %)—and subfreezing temperatures (263 K and 253 K). Using a combination of techniques of molecular microbiology and aqueous geochemistry, we evaluated the potential roles of proteins over- or underexpressed as important players in different mechanisms for the adaptability of life to cold environments. We recorded the changes observed by micro-differential scanning calorimetry. Unfortunately, Rhodococcus sp. JG3 did not show our hypothesized effect on the melting characteristics of cold Mg-perchlorate solutions. However, the question remains as to whether our novel hypothesis that halophilic/psychrophilic bacteria or archaea can alter the freezing/melting curve of salt solutions could be validated. The null result obtained after analyzing just one case lays the foundation to continue the search for proteins produced by microorganisms that thrive in very cold, high-saline solutions, which would involve testing different microorganisms with different salt components. The immediate implications for the habitability of Mars are discussed.

中文翻译：

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嗜盐和嗜冷微生物能否改变冷咸溶液的冻结/融化曲线？对火星宜居性的影响。

我们提出了这样的假设：微生物可以通过蛋白质表达来改变冷盐溶液的冻结/融化曲线，因为众所周知，蛋白质可以影响液体向冰的转变，这种能力可能对地球上的生物具有生态优势。在火星上。我们通过鉴定合适的候选物，即众所周知的嗜热菌和嗜盐细菌Rhodococcus sp ，检验了我们的假设。JG3，并分析其在培养条件下的反应，其中包括与火星有关的特定吸湿盐，即高浓度的Mg（ClO ₄）₂和50 wt％的高氯酸镁溶液在共晶浓度（44 wt％）和亚冰点温度（263 K和253 K）的两端。通过结合分子微生物学和含水地球化学技术，我们评估了蛋白质过表达或过表达在不同机制下对生命适应寒冷环境的重要作用的潜在作用。我们记录了通过微差示扫描量热法观察到的变化。不幸的是，红球菌sp。JG3并未显示出我们对冷的高氯酸镁溶液的熔融特性的假设影响。但是，关于我们的新假设，即嗜盐/嗜冷细菌或古细菌可以改变盐溶液的冻结/融化曲线，仍然存在疑问。仅分析一种情况后获得的无效结果为继续寻找在极冷，高盐溶液中壮成长的微生物产生的蛋白质奠定了基础，这将涉及测试具有不同盐分的不同微生物。讨论了对火星宜居性的直接影响。