The nitrite-dependent anaerobic methane oxidation (n-damo), which couples the anaerobic oxidation of methane to denitrification, is a recently discovered process mediated by "Candidatus Methylomirabilis oxyfera".Until know, M.oxyfera-like bacteria have only been detected in limited lakes and wetlands, and its currently unknown if these bacteria occur in estuarine habitats.In the present study, the distribution, diversity and abundance of M.oxyfera-like bacteria were studied in the Jiaojiang Estuary of the East Sea (China) by molecular methods.Both the 16S rRNA and pmoA molecular biomarkers confirmed the occurrence of M.oxyfera-like bacteria in the examined estuary.The recovered 16S rRNA gene sequences showed 91.5-97.2% identity to the M.oxyfera 16S rRNA gene, and the recovered pmoA gene sequences showed 85.1-95.4% identity to the pmoA gene of M.oxyfera.Real-time quantitative PCR further confirmed the occurrence of M.oxyfera-like bacteria in this estuary, varied from 5.80× 104 to 8.35 × 107 copies g (dry weight)-1.Correlation analysis demonstrated that the organic content of the sediment was the most important factor affecting the distribution of M.oxyfera-like bacterial communities in the examined estuarine sediments.This study demonstrated for the first time the existence ofM.oxyfera-like bacteria in estuarine environments, and proved the relationships between the distribution of these bacteria and the estuarine environmental conditions.