A mixed culture performing nitrite-dependent anaerobic methane oxidation and the nitrite removal mechanism revealed by high-throughput sequencing

Abstract

Nitrite-dependent anaerobic methane oxidation (n-DAMO) has been regarded as a promising effective approach to nitrogen removal from wastewater. However, n-DAMO bacteria are very difficult to be enriched in biological wastewater treatment processes. An anaerobic sequencing batch reactor (AnSBR) was introduced in the present study for the enrichment of n-DAMO bacteria with cornfield soil as inoculum. Fed with nitrite (NO2−) and methane as the specific substrates, a NO2− load removal as high as 46.16 mg/(L·d) was obtained in the AnSBR since the 232nd day of enrichment culturing, though the relative abundance of Candidatus Methylomirabilis referring to n-DAMO bacteria was 2.37% in the acclimatized mixed culture. High-throughput sequencing of the obtained mixed culture revealed that the community structure was complex with the coexistence of n-DAMO bacteria, methanotrophs, heterotrophic denitrifying bacteria and hydrolytic fermentation bacteria. Analysis of interactions among the prevalent microbial populations suggested that Candidatus Methylomirabilis had played a key role in the metabolic network of the mixed culture. The research work presented a novel approach to the enrichment of n-DAMO bacteria from cornfield soil and was helpful in understanding the role of n-DAMO bacteria in complex matrices.