Exploration of the metabolic flexibility of glycogen accumulating organisms through metatranscriptome analysis and metabolic characterization

Glycogen accumulating organisms (GAOs) are closely related to the deterioration of en-hanced biological phosphorus removal systems. However, the metabolic mechanisms that drive GAOs remain unclear. Here, the two-thirds supernatant of a reactor were decanted fol-lowing the anaerobic period to enrich GAOs. Long-term monitoring demonstrated that the system was stable and exhibited typical characteristics of GAOs metabolism. Acetate was completely consumed after 60 min of the anaerobic phase. The level of glycogen decreased from 0.20 to 0.14 g/gSS during the anaerobic phase, whereas the level of glycogen signifi-cantly increased to 0.21g/gSS at the end of the aerobic period. Moreover, there was almost no phosphate release and absorption in the complete periods, thus confirming the success-ful construction of a GAOs enrichment system. Microbial community analysis demonstrated that Ca. Contendobacter was among the core functional genera and showed the highest ac-tivity among all of the communities. Furthermore, our study is the first to identify the in-volvement of the ethyl-malonyl-CoA pathway in the synthesis of polyhydroxyvalerate via croR, ccr, ecm, mcd, mch and mcl genes. The Embden-Meyerhof-Pamas (EMP) pathway was preferentially used via glgP. Furthermore, the glyoxylate cycle was the main source of ATP under anaerobic conditions, whereas the tricarboxylic acid cycle provided ATP under aero-bic conditions. aceA and mdh appeared to be major modulators of the glyoxylate pathway for controlling energy flow. Collectively, our findings not only revealed the crucial metabolic mechanisms in a GAOs enrichment system but also provided insights into the potential application of Ca. Contendobacter for wastewater treatment. (c) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

This study investigates the metabolic mechanisms of glycogen accumulating organisms (GAOs) and reveals the crucial metabolic pathways in a GAOs enrichment system. It also provides insights into the potential application of Ca. Contendobacter for wastewater treatment.