Studies on the transformation of selected polychlorinated biphenyl congeners by Pseudomonas strain LB 400

Abstract

Resting cells of Pseudomonas strain LB400 are known to transform polychlorinated biphenyls (PCBs) when the cells are previously grown on biphenyl. In this study, PCB transformation was also observed in resting cells grown on other substrates such as glucose and glycerol. The presence of PCB congeners in the growth medium increased the lag phase for the growth of cells on a biphenyl substrate but not on a glycerol substrate. Supplementation of the degradation medium with biphenyl dramatically decreased the rate of PCB congener transformation, while the presence of glycerol or glucose had little or no effect on PCB transformation rates. Removal rates with biphenyl-grown cells in the standard degradation medium for 2,4,2′,4′-tetrachlorobiphenyl, 2,4,5,2′,5′-pentachlorobiphenyl, and 2,3-dichlorobiphenyl were 1.06, 1.66, and 224 μmol/(L∙h), respectively. Relative rates of transformation of 2,3-dichlorobiphenyl by biphenyl-, glucose-, and glycerol-grown cells were 100:36:36 and were similar to the relative rates of transformation of 2,4,5,2′,5′-pentachlorobiphenyl (100:33:42). The presence of PCBs adversely affected cell viability of biphenyl-grown cells over a 48-h incubation period and may explain the decline observed in PCB conversion capacity over the same incubation period. A major objective of this study was to investigate the significance of using biphenyl as the carbon source for growth of Pseudomonas strain LB400 cells capable of PCB transformation. Our findings indicate that, whereas higher rates of transformation of PCBs are observed with biphenyl-grown cells, cells grown on other carbon sources retain PCB-transforming enzymes. In addition, it has been demonstrated that biphenyl inhibits transformation of PCBs by the organism, whereas glycerol or glucose does not.Key words: Pseudomonas strain LB400, polychlorinated biphenyls, degradation, biphenyl.