Degradation of highly chlorinated PCBs byPseudomonas strain LB400

Abstract

Congeners of polychlorinated biphenyl (PCB) differ in the number and position of chlorine substituents. Although PCBs are degraded, those congoners with five or more chlorines have been considered resistant to bacterial degradation. Metabolism byPseudomonas strain LB400 of PCBs representing a broad spectrum of chlorination patterns and having from two to six chlorines was investigated. Degradation of pure PCB congeners and synthetic congener mixes was measured in resting cell assays with biphenyl- or Luria broth-grown cells. In addition, the appearance of metabolites was followed using HPLC purification, and GC and GC-MS characterization. 2,4,5,2′,4′,5′-[¹⁴C]hexachlorobiphenyl was also used to follow the accumulation of¹⁴C-labeled metabolites. Evidence indicates that LB400 aerobically metabolizes representatives of all major structural classes of PCB's including several congeners which lack adjacent unchlorinated carbon atoms. The mechanisms by which many of these congeners are degraded are not fully understood, but it is apparent that aerobic bacteria can degrade a broader spectrum of PCB congeners than previously believed and that this broad spectrum of degradative competence can exist in a single strain.