Multi-omics analysis of nitrifying sludge under carbon disulfide stress: Nitrification performance and molecular...

Carbon disulfide (CS₂) is a widely used enzyme inhibitor with cytotoxic properties, commonly employed in viscose fibers and cellophane production due to its non-polar characteristics. In industry, CS₂ is often removed by aeration, however, residual CS₂ may enter the wastewater treatment plants, impacting the performance of nitrifying sludge. Currently, there is a notable dearth of research on the response of nitrifying sludge to CS₂-induced stress. This study delves into the alterations in the performance of nitrifying sludge under short-term and long-term CS₂ stress, scrutinizes the toxic effects of CS₂ on microbial cells, elucidates the succession of microbial community structure, and delineates changes in microbial metabolic products. The findings from short-term CS₂ stress revealed that low concentrations of CS₂ induced oxidative stress damage, which was subsequently repaired in cells. However, at concentrations of 100-200 mg/L, CS₂ inhibited reactive oxygen species, superoxide dismutase, and catalase, which are associated with metabolic and antioxidant activities. The inhibition of nitrite oxidoreductase activity by high concentrations of CS₂ was attributed to its impact on the enzyme's conformation. Prolonged CS₂ stress resulted in an increase in the secretion of soluble extracellular polymeric substances in sludge, while CS₂ was assimilated into sulfate. The analysis of sludge microbial community structure revealed a decline in the relative abundance of Rhodanobacter, which is associated with nitrification, and an increase in Sinomonas, involved in sulfur oxidation. Metabolite analysis results demonstrated that high concentrations of CS₂ affect pantothenate and CoA biosynthesis, purine metabolism, and glutathione metabolism. This study elucidated the microbial response mechanism of nitrifying sludge under short-term and long-term CS₂ stress. It also clarified the composition and function of microbial ecosystems, and identified key bacterial species and metabolites. It provides a basis for future research to reduce CS₂ inhibition through approaches such as the addition of metal ions, the selection of efficient CS₂-degrading strains, and the modification of strain metabolic pathways.