Multi-omics analysis reveals the mechanisms by which C6-HSL enhances the resistance of typical functional bacteria in activated sludge to low-temperature stress.

Signaling molecules, particularly acyl-homoserine lactones (AHLs), can enhance microbial activity under low-temperature stress. However, the specific mechanisms underlying this effect remain unclear. This study identified a typical activated sludge functional bacterium that is sensitive to low temperatures and regulated by hexanoyl-L-homoserine lactone (C6-HSL), a representative of AHLs. It elucidates how C6-HSL modulates the bacterium's resistance to low-temperature stress. Experimental results indicated that C6-HSL significantly increased the levels of adenosine triphosphate (ATP), superoxide dismutase (SOD), peroxidase (POD) and glutathione peroxidase (GSH-Px) in strain LB-001 under low-temperature stress, while also decreasing the levels of reactive oxygen species (ROS). Additionally, C6-HSL markedly repaired the damage to cell membrane structure caused by low-temperature stress. At the genetic level, C6-HSL upregulated the expression of 20 key genes related to energy metabolism, antioxidation, and fatty acid synthesis. At the metabolic level, C6-HSL increased the levels of metabolites related to energy metabolism and antioxidation, boosted the content of unsaturated fatty acids, and reduced the content of saturated fatty acids. This study utilized C6-HSL and low-temperature induction in conjunction with 16S microbial diversity sequencing, genomics, transcriptomics, and metabolomics. These methods were employed to elucidate the molecular mechanisms by which exogenous C6-HSL regulates the resistance of activated sludge microbial communities to low-temperature stress. This research lays the foundation for the application of AHLs and cell communication in wastewater biological treatment, fostering deeper exploration and further innovation in related academic research.