Carbon fixation from mineral carbonates.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 29044115.
- Also identified by DOI 10.1038/s41467-017-00703-4 and PMC identifier 5715163.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
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<sub>2</sub> 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<sub>2</sub>. 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.