PDF(Pubmed)
Abstract：
Past and present habitability of Mars have been intensely studied in the context of the search for signals of life. Despite the harsh conditions observed today on the planet, some ancient Mars environments could have harbored specific characteristics able to mitigate several challenges for the development of microbial life. In such environments, Fe2+ minerals like siderite (already identified on Mars), and vivianite (proposed, but not confirmed) could sustain a chemolithoautotrophic community. In this study, we investigate the ability of the acidophilic iron-oxidizing chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans to use these minerals as its sole energy source. A. ferrooxidans was grown in media containing siderite or vivianite under different conditions and compared to abiotic controls. Our experiments demonstrated that this microorganism was able to grow, obtaining its energy from the oxidation of Fe2+ that came from the solubilization of these minerals under low pH. Additionally, in sealed flasks without CO2, A. ferrooxidans was able to fix carbon directly from the carbonate ion released from siderite for biomass production, indicating that it could be able to colonize subsurface environments with little or no contact with an atmosphere. These previously unexplored abilities broaden our knowledge on the variety of minerals able to sustain life. In the context of astrobiology, this expands the list of geomicrobiological processes that should be taken into account when considering the habitability of environments beyond Earth, and opens for investigation the possible biological traces left on these substrates as biosignatures.
摘要：
在寻找生命信号的背景下，对火星过去和现在的可居住性进行了深入研究。尽管今天在地球上观察到恶劣的条件，一些古老的火星环境可能具有特定的特征，能够减轻微生物生命发展的几个挑战。在这样的环境中,Fe2+矿物，如菱铁矿（已经在火星上发现），和vivianite(提议，但尚未确认）可以维持化学自养社区。在这项研究中,我们研究了嗜酸性铁氧化化学自养细菌嗜酸氧化亚铁硫杆菌使用这些矿物质作为其唯一能源的能力。氧化亚铁在不同条件下在含有菱铁矿或vivianite的培养基中生长，并与非生物对照进行比较。我们的实验表明这种微生物能够生长，从Fe2的氧化中获得能量，该氧化来自这些矿物质在低pH下的溶解。此外,在没有二氧化碳的密封烧瓶中，氧化亚铁氧能够直接从菱铁矿释放的碳酸根离子中固定碳，用于生物质生产，表明它可以在很少或根本没有接触大气的情况下定居地下环境。这些以前未开发的能力扩大了我们对能够维持生命的各种矿物质的知识。在天体生物学的背景下，这扩大了在考虑地球以外环境的可居住性时应考虑的地球微生物学过程的列表，并打开调查这些底物上可能留下的生物痕迹作为生物特征。
