Divergent structures of carbazole degradative car operons isolated from gram-negative bacteria

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 Pseudonomas 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 CAN and K23, carEF genes did not exist downstream of the car gene cluster of Janthinobacterium sp. strain P. 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 car(J3) and car(KA1) gene clusters, ORFs whose deduced amino acid sequences showed homology to GmR-family transcriptional regulators were identified.