PCB biodegradation and bphA1 gene expression induced by salicylic acid and biphenyl with pseudomonas fluorescence P2W and ralstonia eutropha H850

Organic carbon substrate amendments are promising bioremediation strategies to induce polychlorinated biphenyls (PCB) aerobic degradation. However, their selective induction on PCB degraders has not been well studied. In this study, the substrate interaction effects of salicylic acid and biphenyl on PCB biodegradation were investigated with pure cultured isolates, including a newly isolated Pseudomonas fluorescence (P2W) and the veteran PCB degrader Ralstonia eutropha (H850). A significant biodegradation of lower-chlorinated PCB in H850 was induced by both salicylic acid and biphenyl amendments, while the biodegradation in P2W was induced only by salicylic acid. The binary substrates of salicylic acid and biphenyl resulted in a significantly inhibited effect on PCB removal in both strains. The expression of the functional gene bphA1 in the upper biphenyl degradation pathway was further investigated by quantitative reverse transcription PCR. Compared to H850, P2W had higher expression in the bphA1 gene induced mainly by salicylic acid rather than biphenyl. Particularly, the binary substrate induction led to an excessive expression of bphA1 gene in both strains, which was in good agreement with their biomass growth. These results suggested that the special induction of PCB biodegradation depends on the selection of organic carbon substrates and the acclimation of degrader strains.