Transcriptional regulation of several genes for bacteriochlorophyll biosynthesis in Rhodopseudomonas capsulata in response to oxygen.

Although it has been shown that bacteriochlorophyll synthesis in Rhodopseudomonas capsulata is repressed by oxygen and high light intensity, few details of regulation by these environmental factors are known, primarily owing to a lack of assays for the biosynthetic enzymes. We have examined regulation at the transcriptional level by isolating and studying fusions between the Mu d1(Apr lac) phage and various bch genes. In these strains, the lacZ gene of the phage is under the control of bch gene promoters. We have found that atmospheric oxygen tension (20% O2) reduces the expression of these fusions at least twofold compared with low oxygen tension (2% O2). Therefore, transcription of the bchA, bchB, bchC, bchG, and bchH genes is regulated in response to oxygen.