Metabolic exploration of glycogen accumulating organisms' sludge with Candidatus Contendobacter in enhanced...

Competition between glycogen-accumulating organisms (GAOs) and polyphosphate-accumulating organisms (PAOs) may significantly contribute to the deterioration of enhanced biological phosphorus removal (EBPR). However, the metabolic shift of GAOs sludge from glycogen accumulating metabolism (GAM) to polyphosphate accumulating metabolism (PAM) through operational mode conversion still remains unclear. Here, the model of metabolic shift was constructed by altering the operational mode, and the metabolic characteristic was investigated. Our findings indicated a gradual increase in intracellular poly-P from 0.0125 to 0.0300 g/g SS during mode conversion. Phosphorus release during the anaerobic period surged from 1.739 to 30 mg/L. The system demonstrated the typical characteristics of biological phosphorus removal for 41 days, with 99 % phosphorus consumption occurring within the initial 2 h of the aerobic period. Batch experiments and stoichiometric ratios further validated the phosphorus removal performance, confirming the successful transition of GAOs sludge metabolism from GAM to PAM. Community structure analysis revealed a gradual increase in the highest abundance of Candidatus Accumulibacter to 4.73 %, which was consistently lower than that of Candidatus Contendobacter. The analysis of key genes revealed high expression of ppk, ppa, and hppA genes associated with phosphorus metabolism in Ca. Contendobacter, indicating its involvement in the PAM. Additionally, seven key genes, including phbB, phaJ, ccr, ecm, mcd, mch, and mcl were identified to regulate the synthesis of intracellular storage substances, polyhydroxybutyrate (PHB), and polyhydroxyvalerate (PHV) in Ca. Contendobacter. This study can offer novel insights into the metabolic behavior of Ca. Contendobacter and the optimization of EBPR deterioration.