Southern hybridization analysis of the genomes from the newly-isolated 10 carbazole (CAR)-utilizing bacteria revealed that 8 of the isolates carried gene clusters homologous to the CAR-catabolic car operon of Pseudomonas resinovorans strain CA10. Sequencing analysis showed that two car operons and the neighboring regions of Pseudomonas sp. strain K23 are nearly identical to that of strain CA10. In contrast to strains CA10 and K23, carEF genes did not exist downstream of the car gene cluster of Janthinobacterium sp. strain J3. In the car gene clusters, strains CA10, K23 and J3 have Rieske-type ferredoxin as a component of carbazole dioxygenase, although Sphingomonas sp. strain KA1 possesses a putidaredoxin-type ferredoxin. We confirmed that this putidaredoxin-type ferredoxin CarAc can function as an electron mediator to CarAa of strain KA1. In the upstream regions of the carJ3 and carKA1 gene clusters, ORFs whose deduced amino acid sequences showed homology to GntR-family transcriptional regulators were identified.

Eleven carbazole (CAR)-degrading bacterial strains were isolated from seawater collected off the coast of Japan using two different media. Seven isolates were shown to be most closely related to the genera Erythrobacter, Hyphomonas, Sphingosinicella, Caulobacter, and Lysobacter. Meanwhile, strains OC3, OC6S, OC9, and OC11S showed low similarity to known bacteria, the closest relative being Kordiimonas gwangyangensis GW14-5 (90% similarity). Southern hybridization analysis revealed that only five isolates carried car genes similar to those reported in Pseudomonas resinovorans CA10 (car_CA10) or Sphingomonas sp. strain KA1 (car_KA1). The isolates were subjected to GC-MS and the results indicated that these strains degrade CAR to anthranilic acid.