Oxidative dehalogenation and mineralization of polychlorinated biphenyls by a resuscitated strain Streptococcus sp....

Most functional microorganisms cannot be cultivated due to entering a viable but non-culturable (VBNC) state, which limits the characterization and application of polychlorinated biphenyl (PCB)-degrading strains. Resuscitating VBNC bacteria could provide huge candidates for obtaining high-efficient PCB degraders. However, limited studies have focused on the ability of resuscitated strains for PCBs degradation. In the present study, whole-genome analysis of a resuscitated strain SPC0, and its performances in degradation of three prevalent PCB congeners (PCBs 18, 52 and 77) were investigated. The results indicate that the strain SPC0 belonged to the genus Streptococcus, possessed the degradation potential for aromatic xenobiotics. The SPC0 could effectively degrade PCBs 18 and 52, but exhibited lower degradation efficiency of PCB 77. Degradation of PCBs 18 and 52 could be fitted well by zero-order model, whereas the fittest model for PCB 77 degradation was pseudo second-order kinetics. The bph genes expression, chloride ions release and degradation metabolites identification, suggest that SPC0 possessed the capability of oxidative dehalogenation and mineralization of PCBs. Interestingly, SPC0 can degrade PCBs via the bph-encoded biphenyl pathway, and further mineralize metabolite dichlorobenzoate via protocatechuate pathway. This study is the first to show that a strain belonging to genus Streptococcus possessed PCB-degrading capability, which uncovered the powerful potential of resuscitated strains for bioremediation of PCB-contaminated sites.