Biological treatment of waste polychlorinated biphenyls (PCBs) mixed with organic solvents (OSs) requires bacteria that have both OS tolerance and PCB-degrading capacity . Therefore, we tried to find such bacteria strongly capable of both tolerating OS and degrading PCBs . We screened eleven bacteria capable of degrading more than 70% (w/v) of KC-300 containing 10ppm PCB from 200 samples of soil and sea water taken from the mouth of Sagami river and elsewhere. We selected six of the 11 strains

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... hat could degrade more than 50 % (w/v) of KC-500 (10 ppm) . The six strains were subjected to experiments using high concentrations of PCBs (HC-PCBs) and OS tolerance tests. Of these six , a strain that could degrade HC-PCBs was selected, and identified by physiological , biological and electron microscopic examinations as Pseudomonas putida. The isolate was then named SN-4992. SN-4992 degraded more than 60% of PCBs at 100 ppm (KC-400) over 15 d, and 86.8 % of very toxic coplanar PCBs (c-PCBs) in KC-400 (100 ppm) .