Abstract:[Background] Most cold-tolerant bacteria are isolated from activated sludge. Understanding the response of activated sludge consortia to low temperatures contributes to the domestication of cold-tolerant bacteria. [Objective] Anammox consortia was studied as the research object to study the effects of decreasing temperature on metabolic pathways and metabolites of anammox consortia, in order to explain the response mechanism of anammox consortia to decreased temperature. [Methods] The anammox sludge was domesticated at 25 °C and 35 °C to study the effects of temperature on the nitrogen removal performance of the reactors, bacterial activity and biomass yield, and community structure. Metabolite abundance and metabolic pathway activity of anammox consortia were compared under two temperatures by metabolomics. [Results] Under decreased temperature, although CO2 fixation, TCA cycle and pyruvate metabolism of anammox consortia were down-regulated, which led to a significant decrease in nitrogen removal activity and biomass yield. However, RNA synthesis level, and synthesis of putrescine and signal molecules were up-regulated, thereby regulating the metabolism of the consortia to adapt to the low temperature through transcriptional regulation, regulation of membrane lipid composition and changes in membrane structure. [Conclusion] The physiological mechanism of anammox consortia adapting to low temperature was explored from the perspective of molecular mechanism, and the important role of putrescine and signal molecules in the adaptation of sludge consortia to low temperature was explained for the first time.
