NOVEL CARBAZOLE DEGRADATION GENES OF SPHINGOMONAS CB3 - SEQUENCE-ANALYSIS, TRANSCRIPTION, AND MOLECULAR ECOLOGY

The degradation of aromatic compounds by bacteria is dependent upon sp ecific catabolic operons, The unique car locus isolated from Sphingomo nas CB3 encodes the first four enzymes involved in the catabolism of t he azaarene carbazole, These include a class II three-component dioxyg enase enzyme system, a dihydrodiol dehydrogenase, an extradiol (meta-c leavage) dioxygenase, and a hydrolase, Homology of deduced amino acid sequences is closer to corresponding biphenyl catabolic genes than to previously characterised carbazole degradation genes. Gene arrangement is also identical to that found in some bph loci, The car genes are t ranscribed when carbazole is utilised as a sole carbon source, and alt hough biphenyl does not serve as a growth substrate for Sphingomonas C B3 it is able to act as a non-metabolisable inducer of the car locus. Ecologically the car genes were detected in polycyclic aromatic hydroc arbon (PAH) contaminated soil associated with a former town gas site. (C) 1998 Academic Press.