Adaptation of Cornamonas testosteroni TAM1 to utilize phenol: organization and regulation of the genes involved in phenol degradatio

Abstract

SUMMARY: Comamonas testosteroni TAU1 was not able to grow on phenol as a sole carbon and energy source, but it gained the ability to utilize phenol after a 2-3-week incubation in a medium containing phenol. Phenol hydroxylase (PH) and catechol2,3-dioxygenase (C230) were highly induced by phenol in the adapted strain designated as strain P1, suggesting that phenol was degraded via the meta-pathway. Gene clusters for phenol degradation were isolated from both strains TAU1 and P1. The structural genes encoding multi- component PH and C230 (aphKLMNOPQB), and a regulatory gene of the NtrC family (aphR), were located in a divergent transcriptional organization. The cloned aphKLMNOPQl3 genes from either strain TAU1 or strain P1 produced active PH and C230 enzymes in strain TA441. No difference was found between the strains in the sequences of aphR and the intergenic promoter region of aphK and aphR. However, the transcriptional activities of the aphK and aphR promoters were higher in strain P1 than in strain TA441. The aphK-promoter activity was not observed in aphR mutant strains and these strains could not grow on phenol. The aphR mutant of strain P1 was able to grow on phenol after transformation with a recombinant aphR gene but strain TAM1 was not, suggesting that the expression of the aph genes is silenced by an unidentified repressor in strain TAU1 and that this repressor is modified in strain P1.