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.
The carbazole-degrading marine bacterium OC6ST was isolated from seawater collected off the coast of Kobe, Japan. Phylogenetic analysis of 16S rRNA revealed that this strain is distinct from other known orders of class ‘Alphaproteobacteria’. The closest related bacterium was Kordiimonas gwangyangensis GW14-5T, although 16S rRNA similarity was only 90.1%. Strain OC6ST was Gram-negative, motile, rod-shaped, catalase-positive, oxidase-positive, nitrate-reducing, and mesophilic. Respiratory quinone was Q-10 for both aerobic and anaerobic growth, and the DNA G+C content was 58.3 mol%. Optimal cell growth was observed at 16-37 °C, pH 5.5-10, and at NaCl concentrations up to 5%. The dominant fatty acids were C18 : 1 ω7c (41.54%), C14 : 0 2-OH (14.21%), and C17 : 1 ω6c (10.10%). The results suggest that this marine bacterium may be representing a novel genus and species within ‘Alphaproteobacteria’.
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