Jonathan Willett
Undergraduate Student

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Rhodobacter capsulatus is a purple photosynthetic bacterium that can survive in a variety of environmental conditions. Although R. capsulatus can respire under both aerobic and anaerobic growth conditions, it relies primarily on anoxygenic photosynthesis when illuminated under anaerobic conditions. Regulation of the photosystem is transcriptionally controlled, primarily in response to changes in availability of oxygen. Oxygen is sensed through a two-component regulatory system, RegB/RegA, which control photosynthesis, carbon fixation, nitrogen assimilation, formaldehyde dehydrogenase, hydrogenase, DMSO reductase, nitrite reductase, cytochrome oxidase and electron transport. In this study, we provide genetic and biochemical evidence that the RegB/RegA two-component system has a role in coordinating expression of genes encoding enzymes for bacteriochlorophyll, carotenoid and heme biosynthesis. Through DNase I protection assays, ß -galactosidase assays, and primer extension we show that RegB/RegA exerts transcriptional regulation of the bchE, crtI and bchD promoters. These results, coupled with previous studies indicates that RegB/RegA has a major role in coordinating expression of enzymes in the heme, bacteriochlorophyll and carotenoid biosynthetic pathways with cytochrome and photosystem apoproteins that bind these cofactors.