Contrasting community stability and functional dynamics of denitrifying anaerobic methane-oxidizers in rivers

The denitrifying anaerobic methane oxidation (DAMO) process, driven by DAMO bacteria and DAMO archaea, plays a vital role in mitigating methane emissions in river ecosystems. However, the community stability and functional dynamics of these DAMO microorganisms under different hydrological conditions remain poorly understood. This study explored the community structure, metabolic activity, and functional gene expression of DAMO microorganisms in major rivers of the Taihu Basin across different hydrological seasons. Amplicon sequencing demonstrated the presence of diverse DAMO microorganisms in these rivers. The richness and community structure of DAMO archaea exhibited more significant variations than those of DAMO bacteria. Co-occurrence network analysis further indicated that DAMO bacterial communities were more robust and less vulnerable than their archaeal partners, thereby exhibiting a higher level of stability. Similar functional dynamics of DAMO microorganisms were revealed through microcosm incubations using isotopic labeling, along with transcriptional analysis of functional genes. Methane oxidation activity and mcrA gene expression in DAMO archaea varied significantly across seasons (p < 0.05), whereas DAMO bacterial activity and pmoA expression remained largely stable (p > 0.05). The redundancy analysis followed by the hierarchical partitioning analysis demonstrated that oxygen exerted more impact on DAMO archaeal communities (60.2 %) than on DAMO bacterial communities (28.0 %), indicating the oxygen tolerance might be a possible reason for divergent ecological patterns. Taken together, this study presented novel insights into the differential responses of DAMO microbial communities to hydrological fluctuations in river ecosystems.