Metagenomics analysis of ecosystem integrating methane and sulfide generation in urban sewer systems

Simultaneous generation of methane and sulfide is a major concern affecting sewer system operations, and the methanogenic archaea and sulfate-reducing bacteria may increase methane and sulfide production via their symbiotic activities. However, interactions between methane and sulfide metabolism are unclear. In this study, 18 high-quality draft genomes from sewer biofilms were obtained via genome-resolved metagenomics (Binning). The assembled bins 1, 5, 10, 12 and 15 contained abundant ackA, mcrA, mtsA, mtsB and serA genes were involved in methane generation, sulfide consumption via methane metabolism and sulfide metabolism to promote methane generation. Because of the independent and single functionality of these bins, they formed a bio-symbiotic system to promote methane and sulfide generation. Interestingly, for bins 2, 3, 8 and 9, the functions of methane generation, sulfide generation and sulfide consumption via methane metabolism occurred simultaneously. The community affiliations of the assembled bins were also unusual. For instance, bin 9 (Ignavibacteria bacterium) was derived from the Ignavibacteriae supercluster that was not been detected in sewer biofilms, but participated in both methane generation and sulfide consumption. Therefore, these bins formed another biological system with multiple functional aggregates. Two types of ecosystems integrating methane and sulfide generation in sewers were proposed. Our results improve the understanding of toxic gas emissions in sewers and provide a theoretical foundation for studies on gas suppression.