Cometabolism of polychlorinated biphenyls: enhanced transformation of Aroclor 1254 by growing bacterial cells

Acinetobacter sp. strain P6 and a soil isolate, Arthrobacter sp. strain B1B, were tested for their ability to transform Aroclor 1254 as washed resting cells and as growing cells with biphenyl as the substrate. Growing cells were far superior to resting-cell suspensions in terms of total polychlorinated biphenyl (PCB) transformation, transformation of specific PCB congeners, and diversity of congeners that were attacked. Growing cells of Acinetobacter sp. strain P6 and Arthrobacter sp. strain B1B transformed 32 and 23% of the [14C]Aroclor 1254, respectively, whereas resting cells of the same respective cultures transformed only 17 and 8%. Transformation was significantly greater with resting cells in only 2 of 39 cases in which congeners were transformed by both growing and resting cells of both cultures. The components of 19 and 12 capillary gas-chromatographic peaks of Aroclor 1254 were transformed by biphenyl-grown resting cells of Acinetobacter sp. strain P6 and Arthrobacter sp. strain B1B, respectively, whereas the components of an additional 6 and 7 peaks were attacked by growing cells of the same respective cultures. Biphenyl oxidation by resting cells of both cultures decreased with time to less than 8% in 28 h. In addition to the normal 2,3-dioxygenase attack on PCBs, Acinetobacter sp. strain P6 also attacked congeners lacking an open 2,3-position. The ability of Acinetobacter sp. strain P6 to transform the components of 25 of the 40 largest peaks of Aroclor 1254 makes it one of the most versatile PCB-transforming organisms yet reported.