FIG. 20.

Transcriptional organization and regulation of the bzd cluster of Azoarcus sp. strain CIB. The genes are grouped into two operons, the bzdR regulatory operon (blue) and the bzdNOPQMSTUVWXYZA catabolic operon (orange), controlled by the P_R and P_N promoters, respectively. Both promoters are repressed by the BzdR protein (blue), with benzoyl-CoA being the inducer molecule. The activation of the P_N promoter under anaerobic conditions is also dependent on the AcpR protein (violet). Some carbon sources, such as organic acids, cause catabolite repression at the P_N promoter via BzdR and a still-unknown factor (?). The − and + symbols represent transcriptional repression and activation, respectively.