Isolation of highly efficient microorganism strains for degrading chlorinated compounds is the key to successful bioremediation of highly chlorinated contaminants in the environment.A gram-negative bacterium,Enterobacter sp LY402,was isolated from soil contaminated with electric transformer oil.The results of 16S rDNA analysis showed the bacterium is 99% homology to Enterobacter hormaechei.Laboratory experiments have showed that the strain LY402 was capable of aerobically transforming 79 of the 91 major congeners of a polychlorinated biphenyl (PCB) mixture of Aroclor 1242,1254,and 1260 within a short period of time.