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

Sulfate reduction has long been considered a leading cause of hydrogen sulfide (HS) emissions from composting, causing serious air pollution and health threats. HS biogenesis through cysteine cleavage is a known pathway for bacteria to resist oxidative stress. However, whether the biogenesis pathway exacerbates HS 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 HS production during composting with different aeration rates. We found that PAG addition significantly inhibited HS emission by 45.52 % and 19.74 % at high and low aeration rates, respectively. PAG addition reduced the diversity of core bacteria associated with HS 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 HS production, and PAG inhibited both pathways. Finally, microbial pure culture experiment further verified the effectiveness of PAG in reducing HS emission of composting. This work reveals an overlooked pathway for HS production during composting, which fills the research gap in the role of the biogenesis pathway in composting HS emission. This provides breakthrough guidance for future environmental management and pollution control at source.