Multi-omics reveal an overlooked pathway for H₂S production induced by bacterial biogenesis from composting

Sulfate reduction has long been considered a leading cause of hydrogen sulfide (H₂S) emissions from composting, causing serious air pollution and health threats. H₂S biogenesis through cysteine cleavage is a known pathway for bacteria to resist oxidative stress. However, whether the biogenesis pathway exacerbates H₂S emission during composting with dramatic temperature changes and oxidative stress is largely unknown. Here, we used DL-propargylglycine (PAG), an inhibitor of cysteine lyase (cystathionine γ-lyase), to explore the contribution of biogenesis pathway to H₂S production during composting with different aeration rates. We found that PAG addition significantly inhibited H₂S emission by 45.52 % and 19.74 % at high and low aeration rates, respectively. PAG addition reduced the diversity of core bacteria associated with H₂S production. Metagenomic and metaproteomic analysis further revealed that PAG decreased the abundance of sulfate reduction genes, down-regulated the expression of cysteine lyases, and up-regulated the catalase expression. Therefore, both sulfate reduction and biosynthesis contributed to the H₂S production, and PAG inhibited both pathways. Finally, microbial pure culture experiment further verified the effectiveness of PAG in reducing H₂S emission of composting. This work reveals an overlooked pathway for H₂S production during composting, which fills the research gap in the role of the biogenesis pathway in composting H₂S emission. This provides breakthrough guidance for future environmental management and pollution control at source.