Oxygen-associated differentiation of TBBPA-transforming activated sludge consortia and characterization of a cultivable Klebsiella degrader.

Tetrabromobisphenol A (TBBPA), a widely used brominated flame retardant, poses increasing environmental and health concerns, yet how oxygen availability is associated with the assembly and degradation potential of TBBPA-transforming microbiomes remains poorly resolved. Here, ten enrichment consortia (six aerobic and four anaerobic) were established from activated sludge collected at six municipal wastewater treatment plants, achieving up to 63.46% TBBPA removal at an initial concentration of 5 mg/L. Metagenomic analysis revealed marked community divergence between the aerobic and anaerobic enrichment conditions, with Burkholderia predominating in the aerobic consortia and Klebsiella predominating in the anaerobic consortia. Read-mapping-based abundance profiling detected the HY4.102-affiliated Klebsiella pneumoniae population under both oxygen conditions, with higher relative abundance in the anaerobic consortia. Strain NCHT, isolated from the aerobic consortium NC_H, shared >99% ANI and AAI with HY4.102 and transformed TBBPA under both aerobic and anaerobic batch conditions. During aerobic incubation, strain NCHT transformed 51.0-68.4% of TBBPA across the tested concentrations, and UHPLC-MS/MS analysis yielded 17 putatively identified transformation intermediates consistent with an interconnected network involving debromination, hydroxylation, O-methylation, and β-scission. Molecular docking further prioritized DhmA, GSTs, CbdA/B, and PobB as candidate enzymes for debromination and downstream aromatic transformation, broadly consistent with the dehalogenation-related genes annotated in MAG HY4.102. Together, these findings provide an integrated community-to-strain framework for investigating TBBPA transformation.