Metabolic versatility of aerobic methane‐oxidizing bacteria under anoxia in aquatic ecosystems.

The potential positive feedback between global aquatic deoxygenation and methane (CH4) emission emphasizes the importance of understanding CH4 cycling under O2‐limited conditions. Increasing observations for aerobic CH4‐oxidizing bacteria (MOB) under anoxia have updated the prevailing paradigm that MOB are O2‐dependent; thus, clarification on the metabolic mechanisms of MOB under anoxia is critical and timely. Here, we mapped the global distribution of MOB under anoxic aquatic zones and summarized four underlying metabolic strategies for MOB under anoxia: (a) forming a consortium with oxygenic microorganisms; (b) self‐generation/storage of O2 by MOB; (c) forming a consortium with non‐oxygenic heterotrophic bacteria that use other electron acceptors; and (d) utilizing alternative electron acceptors other than O2. Finally, we proposed directions for future research. This study calls for improved understanding of MOB under anoxia, and underscores the importance of this overlooked CH4 sink amidst global aquatic deoxygenation. [ABSTRACT FROM AUTHOR]