Psychrotolerant bacteria isolated from arctic soil that degrade polychlorinated biphenyls at low temperatures

Psychrotolerant polychlorinated biphenyl (PCB)-degrading bacteria were isolated at 7 degreesC from PCB-contaminated Arctic soil by using biphenyl as the sole organic carbon source. These isolates were distinguished from each other by differences in substrates that supported growth and substrates that were oxidized. 16S ribosomal DNA sequences suggest that these isolates are most closely related to the genus Pseudomonas. Total removal of Aroclor 1242, and rates of removal of selected PCB congeners, by cell suspensions of Arctic soil isolates and the mesophile Burkholderia cepacia LB400 were determined at 7, 37, and 50 degreesC. Total removal values of Aroclor 1242 at 7 degreesC by LB400 and most Arctic soil isolates were similar (between 2 and 3.5 &mgr;g of PCBs per mg of cell protein). However the rates of removal of some individual PCB congeners by Arctic isolates were up to 10 times higher than corresponding rates of removal by LB400. Total removal of Aroclor 1242 and the rates of removal of individual congeners by the Arctic soil bacteria were higher at 37 degreesC than at 7 degreesC but as much as 90% lower at 50 degreesC than at 37 degreesC. In contrast, rates of PCB removal by LB400 were higher at 50 degreesC than at 37 degreesC. In all cases, temperature did not affect the congener specificity of the bacteria. These observations suggest that the PCB-degrading enzyme systems of the bacteria isolated from Arctic soil are cold adapted.