Novel Antarctic chemolithotroph drives iron biomineralization.

In Holocene sediments beneath the Larsen C Ice Shelf, Candidatus Mariimomonas ferrooxydans is linked to Fe(II) oxidation via the Cyc2 outer-membrane oxidase, experimentally confirmed.

• Why it matters: Iron oxidation mechanisms and the microbes driving iron biomineralization remain incompletely resolved, and modern settings can reveal processes relevant to ancient banded iron formation.
• What they did: The study profiled stratigraphic microbiomes across laminated facies with iron-containing crystalline illite, then used metagenomics and metagenome-assembled genomes to identify Cyc2 and confirm its Fe(II)-oxidation activity experimentally.
• The result: Microbial community phases tracked environmental transitions, and chemolithotrophic metabolisms in largely anoxic sub-ice shelf sediments imply LCIS preserves a dynamic record of microbial iron mineralization.

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