Microbial Mediation of Carbon, Nitrogen, and Sulfur Cycles During Solid Waste Decomposition

Landfills are a unique terrestrial ecosystem and serve as a significant carbon sink. Microorganisms convert biodegradable substances in municipal solid waste (MSW) to CH4, CO2, and microbial biomass, consisting of the carbon cycling in landfills. Microbial-mediated N and S cycles are also the important biogeochemical process during MSW decomposition, resulting in N2O and H2S emission, respectively. Meanwhile, microbial-mediated N and S cycles affect carbon cycling. How microbial community structure and function respond to C, N, and S cycling during solid waste decomposition, however, are not well-characterized. Here, we show the response of bacterial and archaeal community structure and functions to C, N, and S cycling during solid waste decomposition in a long-term (265 days) operation laboratory-scale bioreactor through 16S rRNA-based pyrosequencing and metagenomics analysis. Bacterial and archaeal community composition varied during solid waste decomposition. Aerobic respiration was the main pathway for CO2 emission, while anaerobic C fixation was the main pathway in carbon fixation. Methanogenesis and denitrification increased during solid waste decomposition, suggesting increasing CH4 and N2O emission. In contract, fermentation decreased along solid waste decomposition. Interestingly, Clostridiales were abundant and showed potential for several pathways in C, N, and S cycling. Archaea were involved in many pathways of C and N cycles. There is a shift between bacteria and archaea involvement in N-2 fixation along solid waste decomposition that bacteria Clostridiales and Bacteroidales were initially dominant and then Methanosarcinales increased and became dominant in methanogenic phase. These results provide extensive microbial mediation of C, N, and S cycling profiles during solid waste decomposition.

Automated summary

Landfills are important terrestrial ecosystems that act as significant carbon sinks. Microorganisms play a crucial role in the decomposition of solid waste, converting biodegradable substances into CH4, CO2, and microbial biomass. They also mediate the nitrogen and sulfur cycles, resulting in the emission of N2O and H2S. However, the response of microbial community structure and function to carbon, nitrogen, and sulfur cycling during solid waste decomposition is not well understood. In this study, we investigated the bacterial and archaeal community composition and functions during solid waste decomposition using molecular techniques. The results showed changes in the composition of bacterial and archaeal communities, as well as shifts in metabolic pathways and cycling processes. These findings highlight the extensive microbial mediation of carbon, nitrogen, and sulfur cycling profiles during solid waste decomposition.