Influence of Soluble and Mineral Sources of Cobalt on Methanogenesis and Growth in Methanosarcina barkeri Fusaro and Methanococcus maripaludis S2.

Methanosarcina barkeri grown on methanol/acetate and Methanococcus maripaludis grown with sulphide both acquire cobalt, iron, and sulphur from cobaltoan pyrite [(Co,Fe)S2] as well as from soluble sources.

• Why it matters: Cobalt is essential for methanogen cofactors, yet sulphidic settings can lock Co into low-solubility minerals like pyrite, limiting one-carbon metabolism.
• What they did: Growth kinetics were tested for M. barkeri across methanogenesis substrates and for M. maripaludis across sulphur sources, then cobalt acquisition from (Co,Fe)S2 was assessed. Direct contact was required to reduce and solubilize Fe and S from (Co,Fe)S2.
• The result: Both strains grew with (Co,Fe)S2 comparable to soluble Co, Fe, and S, and M. barkeri produced an equal amount of cobamides under mineral versus soluble supply. This implies substrate- and sulphur-dependent Co demand and mineral-based nutrient acquisition.

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