Isolation and characterization of a car gene cluster from the naphthalene, phenanthrene, and carbazole-degrading marine isolate Lysobacter sp. strain OC7.

The novel carbazole (CAR)-degrading bacterium Lysobacter sp. strain OC7 has been isolated from seawater and can also utilize naphthalene and phenanthrene as its sole carbon and energy source. The CAR-degradative gene cluster was isolated and encoded five complete open reading frames (ORFs) and two truncated ORFs. Among them, four ORFs showed 40-50% similarity with previously reported CAR-degradative genes. Ferredoxin (carAc) and ferredoxin reductase (carAd) genes, which are necessary for the CAR 1,9a-dioxygenase system, were not found in this car gene cluster. The car (OC7) gene transcripts were strongly detected when CAR was provided. However, these transcripts were also detected when naphthalene was provided. The resting cell reaction with Escherichia coli revealed that CarAa(OC7) can use CarAc and CarAd of Pseudomonas resinovorans CA10 as ferredoxin and ferredoxin reductase, respectively, and converted CAR to 2'-aminobiphenyl-2,3-diol. In 13 marine CAR-degrading isolates, only Caulobacter sp. strain OC6 hybridized with the car (OC7) gene cluster probe. This is the first report showing CAR-degradative genes from the genus Lysobacter.