Oxygen regulation of the ccoN gene encoding a component of the cbb3 oxidase in Rhodobacter sphaeroides 2.4.1T:: Involvement of the FnrL protein

The ccoNOQP gene cluster of Rhodobacter sphaeroides 2.4.1(T) encodes a cbb(3), cytochrome oxidase which is utilized in oxygen-limited conditions for aerobic respiration. The P-galactosidase activity of a ccoN::lacZ transcriptional fusion,vas low under high (30%)-oxygen and anaerobic growth conditions. Maximal ccoN::lacZ expression was observed when the oxygen concentration was lowered to 2%. In an FnrL mutant, ccoN::lacZ expression was significantly lower than in the wild-type pe strain, suggesting that FnrL is a positive regulator of genes encoding the cbb(3) oxidase.