Distinct Microbial Communities Within and On Seep Carbonates Support Long-term Anaerobic Oxidation of Methane and Divergent pMMO Diversity

Methane-seep carbonates, precipitated by anaerobic methane-oxidizing archaea and sulfate-reducing bacteria (ANME-SRB), can harbor active ANME-SRB communities within their interior, acting as methane sink and carbon storage. Carbonates with low methane oxidation activity can reactivate when methane resurges, suggesting carbonates serve as potential long-term methane sinks. Surface communities vary from diverse assemblages to sulfide-oxidizer dominance, or ANME-SRB biofilms, and contain diverse particulate methane monooxygenases, enzymes catalyzing methane, alkane, or ammonia oxidation.