Biphenyl Modulates the Expression and Function of Respiratory Oxidases in the Polychlorinated-Biphenyls Degrader Pseudomonas pseudoalcaligenes KF707.

Pseudomonas pseudoalcaligenes KF707 is a soil bacterium which is known for its capacity to aerobically degrade harmful organic compounds such as polychlorinated biphenyls (PCBs) using biphenyl as co-metabolite. Here we provide the first genetic and functional analysis of the KF707 respiratory terminal oxidases in cells grown with two different carbon sources: glucose and biphenyl. We identified five terminal oxidases in KF707: two c(c)aa ₃ type oxidases (Caa ₃ and Ccaa ₃ ), two cbb ₃ type oxidases (Cbb ₃ 1 and Cbb ₃ 2), and one bd type cyanide-insensitive quinol oxidase (CIO). While the activity and expression of both Cbb ₃ 1 and Cbb ₃ 2 oxidases was prevalent in glucose grown cells as compared to the other oxidases, the activity and expression of the Caa ₃ oxidase increased considerably only when biphenyl was used as carbon source in contrast to the Cbb ₃ 2 oxidase which was repressed. Further, the respiratory activity and expression of CIO was up-regulated in a Cbb ₃ 1 deletion strain as compared to W.T. whereas the CIO up-regulation was not present in Cbb ₃ 2 and C(c)aa ₃ deletion mutants. These results, together, reveal that both function and expression of cbb ₃ and caa ₃ type oxidases in KF707 are modulated by biphenyl which is the co-metabolite needed for the activation of the PCBs-degradation pathway.