Polyphosphate metabolism genes are associated with hydroxyapatite biomineralization capacity in a novel hydrogenotrophic methanogen Methanobacterium AMB_03

Methanobacterium AMB_03 from a serpentinizing environment precipitates carbonate-substituted hydroxyapatite, with early onset at ≥3 mM phosphate and eventual precipitation by 49 weeks.

• Why it matters: Methanogenic archaea are important in sedimentary phosphorus cycling, yet which lineages can biomineralize phosphate as hydroxyapatite is not well resolved.
• What they did: Comparative genomics links AMB_03’s hydroxyapatite capacity to ppk1-mediated polyphosphate synthesis from ATP, while non-mineralizing strains lack ppk1; 320 Methanobacteriota genomes show complete polyP cycling in ~25%.
• The result: In phosphate gradients (0–6 mM), HAp precipitation is preferential at ≥3 mM, correlates with extracellular polymeric substance production and localized pH increases up to 8.08, and Raman spectra confirm carbonate-substituted HAp.

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