Microbes May Have Formed Iron Deposits During Snowball Earth
A team of researchers from Yonsei University and collaborators has uncovered evidence that chemolithotrophic bacteria may have played a crucial role in forming massive iron ore deposits during the Snowball Earth period. This discovery challenges the long-held belief that photosynthetic bacteria were primarily responsible for these formations.
The team retrieved a 2.4-meter sediment core from beneath Antarctica's Larsen C Ice Shelf. The core, spanning approximately 12,000 years, revealed a new lineage of bacteria, provisionally named Candidatus Mariimomonas ferrooxydans. These microbes were found to oxidize iron from Fe(II) to Fe(III) using a Cyc2 porin-cytochrome fusion protein, a process confirmed through experiments involving E. coli.
This finding suggests that during periods when sunlight and oxygen were scarce, such as the Snowball Earth glaciations, these bacteria may have facilitated iron oxidation and deposition independently of photosynthesis. The research supports a model where chemolithotrophic microbes could have driven banded iron formation (BIF) deposition under ice-covered oceans.