Growth of the genetically engineered strain Cupriavidus necator RW112 with chlorobenzoates and technical chlorobiphenyls.

Cupriavidus necator (formerly Ralstonia eutropha) strain H850 is known to grow on biphenyl, and to co-oxidize congeners of polychlorinated biphenyls (PCBs). Using a Tn5-based minitransposon shuttle system and the TOL plasmid, the rational construction of hybrids of H850 was achieved by subsequent introduction of three distinct elements carrying 11 catabolic loci from three other biodegrading bacteria into the parent strain, finally yielding C. necator RW112. The new genetic elements introduced into H850 and its derivatives were tcbRCDEF, which encode the catabolic enzymes needed for chlorocatechol biodegradation under the control of a transcriptional regulator, followed by cbdABC, encoding a 2-halobenzoate dioxygenase, and xylXYZ, encoding a broad-spectrum toluate dioxygenase. The expression of the introduced genes was demonstrated by measuring the corresponding enzymic activities. The engineered strain RW112 gained the ability to grow on all isomeric monochlorobenzoates and 3,5-dichlorobenzoate, all monochlorobiphenyls, and 3,5-dichloro-, 2,3'-dichloro- and 2,4'-dichlorobiphenyl, without accumulation of chlorobenzoates. It also grew and utilized two commercial PCB formulations, Aroclor 1221 and Aroclor 1232, as sole carbon and energy sources for growth. This is the first report on the aerobic growth of a genetically improved bacterial strain at the expense of technical Aroclor mixtures.