Abstract
In a polychlorinated biphenyl degrader Rhodococcus jostii RHA1, the transcription of bph genes, which are responsble for the degradation of biphenyl (BP)., is activated in the presence of biphenyl. In the previous syudies, it has been revealed that the transcriptional activation of bph genes by BP is repressed in the presence of benzoate (BA), which is one of the meatbolites of BP degradation by RHA1, and that the substrate taht caused the repression is catechol, a lower metabolite of benzoate. In this study, we introduced the catA gene encoding catechol 1, 2-dioxygenase into RHA1 using a plasmid vector, and observed the promoter activity the bphAa gene, which is one of the bph genes, in the presence of BP and BA. We also observed the growth of RHA1 expressing the catA gene in the minimum medium using BP as a sole carbon source. It was shown that the repression of the transcriptional activation by BP in the presence of BA was released by the expression of the catA gene. Moreover, the growth of RHA1 expressing the catA gene on BP was much faster than that of RHA1 with the vector control. From these results, it was shown that the overexpression of the catA gene released the repression of the transcriptional activation of bphAa by catechol, and improved the growth of RHA1 on BP.
