抄録
Xenobiotic degraders play an important role in decomposition of various contaminants in natural environment. We isolated various degraders of carbazole, which is nitrogen-containing heteroaromatic compound contained in coal-tar, creosote, and crude oil, and isolated carbazole degradative car gene clusters from several carbazole-degraders. Among the carbazole degradation pathway reactions, initial deoxygenation catalyzed by carbazole 1,9a-dioxygeanse (CARDO) is very interesting because of its novel regio-selectivity in dioxygenation of carbazole and dioxins. X-ray crystallographic study of the components of CARDO followed by biochemical investigation revealed the mechanisms of substrate recognition by terminal oxygenase component of CARDO and electron transfer from NADH to terminal oxygenase via ferredoxin reductase and ferredoxin. On the other hand, car gene cluster is located on the IncP-7 group conjugative plasmid pCAR1. To understand the behavior of pCAR1 and its molecular mechanism, we carried out the monitoring of pCAR1 itself and pCAR1-having host Pseudomonas strains, and transcriptome analyses of several hosts with or without pCAR1. As the results, we succeeded in detecting novel host responses to having pCAR1. Further analyses suggested the new mechanisms determining the plasmid effects on host cell phenotype.
