Characterization and genetic analyses of a carbazole-degrading gram-positive marine isolate, Janibacter sp. strain OC11

Strain OC11 was isolated from seawater sampled at the coast of Chiba, Japan, in artificial seawater medium with carbazole (CAR) as the sole carbon source. Its 16S ribosomal RNA gene sequence suggested that strain OC11 belongs to the genus Janibacter. The CAR-degradation genes (car genes) of strain OC11 were PCR amplified, using degenerate primers designed based on the car gene sequences of other CAR-degrading bacteria. Complete nucleotide sequences encoding six complete open reading frames were determined, and the first known ferredoxin reductase gene (carAd) was found from a CAR-degrading bacterium isolated from the marine environment. An experiment using a mutant strain suggested that the car genes of strain OC11 are functional in CAR degradation. Southern hybridization indicated that strain OC11 had one car gene cluster in vivo. RT-PCR revealed that transcription of carOC11 constitutes an operon.