Program

Nitrite-dependent anaerobic methane oxidation (n-damo), a recently discovered process, which is mediated by “Candidatus Methylomirabilis oxyfera”, is unique in linking the carbon and nitrogen cycles,and may act as an important and overlooked sink of the greenhouse gas methane in the natural ecosystem. However, the niche and the activity of n-damo bacteria in the mangrove ecosystem have not been confirmed. Here, we report the occurrence of an n-damo process in the mangrove wetland of the Zhangjiang Estuary, China, using molecular and isotopic tracing technologies. The widespread occurrence of n-damo bacteria in mangrove wetland was confirmed using real-time quantitative polymerase chain reaction（qPCR）assay, and the results showed that the abundance of M. oxyfera-like bacterial 16S rRNA and pmoA genes ranged from 2.43×10⁶ to 2.09×10⁷,and 2.07×10⁶ to 3.38×10⁷ copies per gram of dry soil in the examined sediment cores, and the highest amount of targeting genes were all detected in the upper layer (0-20cm).Phylogenetic analyses of n-damo bacterial 16S rRNA and pmoA genes illustrated the depth-specific distribution and high diversity of n-damo bacteria in the mangrove wetland. Stable isotope experiments further confirmed the occurrence of n-damo in the examined mangrove sediments, and the potential n-damo rates ranged from 25.93 to 704.08nmol CO₂ per gram of dry soil per day at different depths of the sediment cores, with the n-damo being more active in the upper layer of the mangrove sediments.Correlation analysis demonstrated that the water content, total organic carbon and total nitrogen of the sediment were significant factors affecting the abundance and activity of n-damo bacteria in mangrove wetland.