Resuscitation-promoting factor stimulates PCB dechlorination and mineralization by Stenotrophomonas sp. FS3 under alternating redox conditions

Bioremediation of highly chlorinated polychlorinated biphenyls (PCBs) typically requires sequential anaerobic-aerobic treatment, highlighting the need for robust facultative anaerobic degraders. In this study, a novel facultative anaerobic strain, Stenotrophomonas sp. FS3, was resuscitated with resuscitation-promoting factor (Rpf) under alternating anaerobic-aerobic conditions. Whole-genome sequencing revealed a comprehensive set of genes for biphenyl, benzoate, catechol, and protocatechuate catabolism, indicating strong intrinsic potential for PCB biodegradation. FS3 achieved 61.2 % removal of Aroclor 1260 at 10 mg/L after 30 days, and Rpf supplementation significantly enhanced both anaerobic dechlorination and aerobic degradation, resulting in a 1.66-fold increase in removal efficiency and greater chloride ion release relative to controls. Viability and morphophysiological analyses revealed that Rpf preserved cell integrity and metabolic activity, preventing the transition into a viable but non-culturable (VBNC) state. Transcriptomic analysis revealed that Rpf supplementation significantly upregulated bph cluster genes and downstream catabolic genes (e.g., pobA , ligB , pcaGH ) without altering the overall degradation pathway, which proceeded via the HOPDA-benzoate pathway followed by catechol- and protocatechuate-mediated mineralization. Collectively, this work establishes FS3 as a robust degrader suitable for PCB bioremediation under fluctuating redox conditions and underscore Rpf supplementation as a viable strategy to enhance the resilience and metabolic capacity of PCB-degrading bacteria.