Department of Geological Sciences, The University of Alabama, Tuscaloosa, AL 35487.
Alabama Museum of Natural History, The University of Alabama, Tuscaloosa, AL 35487.
Proc Natl Acad Sci U S A. 2022 Aug 2;119(31):e2203758119. doi: 10.1073/pnas.2203758119. Epub 2022 Jul 28.
Biominerals are important archives of the presence of life and environmental processes in the geological record. However, ascribing a clear biogenic nature to minerals with nanometer-sized dimensions has proven challenging. Identifying hallmark features of biologically controlled mineralization is particularly important for the case of magnetite crystals, resembling those produced by magnetotactic bacteria (MTB), which have been used as evidence of early prokaryotic life on Earth and in meteorites. We show here that magnetite produced by MTB displays a clear coupled C-N signal that is absent in abiogenic and/or biomimetic (protein-mediated) nanometer-sized magnetite. We attribute the presence of this signal to intracrystalline organic components associated with proteins involved in magnetosome formation by MTB. These results demonstrate that we can assign a biogenic origin to nanometer-sized magnetite crystals, and potentially other biominerals of similar dimensions, using unique geochemical signatures directly measured at the nanoscale. This finding is significant for searching for the earliest presence of life in the Earth's geological record and prokaryotic life on other planets.
生物矿物是地质记录中生命存在和环境过程的重要档案。然而，要将具有纳米尺寸的矿物明确归因于生物成因，这一直具有挑战性。对于磁铁矿晶体来说，特别重要的是确定生物控制的矿化的特征标志，因为这些晶体类似于磁细菌 (MTB) 产生的磁铁矿，它们一直被用作地球上和陨石中早期原核生命的证据。我们在这里表明，MTB 产生的磁铁矿显示出明显的耦合 C-N 信号，而无生命的和/或仿生（蛋白质介导）的纳米级磁铁矿中则不存在这种信号。我们将这种信号的存在归因于与 MTB 形成磁小体有关的蛋白质相关的晶内有机成分。这些结果表明，我们可以使用在纳米尺度上直接测量的独特地球化学特征，将纳米级磁铁矿晶体以及类似尺寸的其他生物矿物赋予生物成因。这一发现对于在地球地质记录中寻找最早的生命存在以及其他行星上的原核生命具有重要意义。
