School of Life Sciences, Arizona State University, Tempe, AZ, 85287, USA.
School of Earth and Space Exploration, Arizona State University, Tempe, AZ, 85287, USA.
Nat Commun. 2017 Oct 18;8(1):1025. doi: 10.1038/s41467-017-00703-4.
Photoautotrophs assimilate oxidized carbon obtained from one of two sources: dissolved or atmospheric. Despite its size, the pool of lithospheric carbonate is not known to be a direct source for autotrophy. Yet, the mechanism that euendolithic cyanobacteria use to excavate solid carbonates suggests that minerals could directly supply CO for autotrophy. Here, we use stable isotopes and NanoSIMS to show that the cyanobacterium Mastigocoleus testarum derives most of its carbon from the mineral it excavates, growing preferentially as an endolith when lacking dissolved CO. Furthermore, natural endolithic communities from intertidal marine carbonate outcrops present carbon isotopic signatures consistent with mineral-sourced autotrophy. These data demonstrate a direct geomicrobial link between mineral carbonate pools and reduced organic carbon, which, given the geographical extent of carbonate outcrops, is likely of global relevance. The ancient fossil record of euendolithic cyanobacteria suggests that biological fixation of solid carbonate could have been relevant since the mid-Proterozoic.
溶解的或大气的。尽管其规模庞大，但地壳碳酸盐库并非已知的自养直接来源。然而，蓝细菌 euendolith 挖掘固体碳酸盐的机制表明，矿物质可以直接为自养提供 CO。在这里，我们使用稳定同位素和 NanoSIMS 表明，蓝藻 Mastigocoleus testarum 的大部分碳来自于它挖掘的矿物质，当缺乏溶解的 CO 时，它更喜欢作为内生菌生长。此外，来自潮间带海洋碳酸盐露头的天然内生群落呈现出与矿物源自养一致的碳同位素特征。这些数据表明了矿物碳酸盐库和还原有机碳之间的直接地质微生物联系，鉴于碳酸盐露头的地理范围，这种联系可能具有全球相关性。蓝细菌 euendolith 的古老化石记录表明，自中元古代以来，固体碳酸盐的生物固定可能就具有相关性。
