Bacterial growth tolerance to concentrations of chlorate and perchlorate salts relevant to Mars
Bacterial growth tolerance to concentrations of chlorate and perchlorate salts relevant to Mars
复制标题
DOI：
10.1017/s1473550416000434
复制
发表时间：
2017-07-01
影响因子：
1.7
通讯作者：
Schneegurt, Mark A.
中科院分区：
文献类型：
--
作者：
Al Soudi, Amer F.;Farhat, Omar;Schneegurt, Mark A.
凤凰号着陆器在火星极地帽发现了相当含量的氯酸盐，这是一种高氯酸盐和Ca， Fe， Mg和Na的氯酸盐的混合物，含量接近0.6%。这些盐具有很强的吸湿性，可以通过潮解形成饱和盐水，很可能在火星上产生冰点非常低的水溶液。为了支持保护地球的努力，我们测量了细菌对氯酸盐的生长耐受性。对俄克拉何马州大盐平原（富含nacl）和华盛顿热湖（富含mgso4）现有的细菌分离株进行了高浓度Mg、K和Na盐（氯酸盐和高氯酸盐）的测试。几乎所有这些耐盐菌株在1%（类似于0.1 M）（每）氯酸盐的浓度下都观察到强劲的生长，与火星上大块土壤中观察到的浓度相似。在高氯酸盐浓度至少为10%（类似于1.0 M）时观察到生长。对氯酸盐的耐受性更强，其生长达到2.75 M（>25%）。对钾盐的耐受性最大，其次是镁盐，然后是钠盐。不同分离株之间的耐受性不同，甚至在相同的系统发育分支中也是如此。耐受性细菌包括在航天器组装设施中发现的属。微生物对氯酸盐的大量耐受性是行星保护的一个问题，因为尽管火星表面附近存在恶劣的化学条件，但污染航天器的耐受性微生物将有更大的生存和扩散机会。
The Phoenix lander at Mars polar cap found appreciable levels of (per)chlorate salts, a mixture of perchlorate and chlorate salts of Ca, Fe, Mg and Na at levels of similar to 0.6% in regolith. These salts are highly hygroscopic and can form saturated brines through deliquescence, likely producing aqueous solutions with very low freezing points on Mars. To support planetary protection efforts, we have measured bacterial growth tolerance to (per)chlorate salts. Existing bacterial isolates from the Great Salt Plains of Oklahoma (NaCl-rich) and Hot Lake in Washington (MgSO4-rich) were tested in high concentrations of Mg, K and Na salts of chlorate and perchlorate. Strong growth was observed with nearly all of these salinotolerant isolates at 1% (similar to 0.1 M) (per)chlorate salts, similar to concentrations observed in bulk soils on Mars. Growth in perchlorate salts was observed at concentrations of at least 10% (similar to 1.0 M). Greater tolerance was observed for chlorate salts, where growth was observed to 2.75 M (>25%). Tolerance to K salts was greatest, followed by Mg salts and then Na salts. Tolerances varied among isolates, even among those within the same phylogenetic clade. Tolerant bacteria included genera that also are found in spacecraft assembly facilities. Substantial microbial tolerance to (per)chlorate salts is a concern for planetary protection since tolerant microbes contaminating spacecraft would have a greater chance for survival and proliferation, despite the harsh chemical conditions found near the surface of Mars.