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.