Map of genes for carotenoid and bacteriochlorophyll biosynthesis in Rhodopseudomonas capsulata.

The recently discovered gene transfer system of Rhodopseudomonas capsulata was used to construct a genetic map of a region concerned with bacteriochlorophyll and carotenoid production. Mutants blocked in the biosynthesis of these compounds were isolated, and each was characterized on the basis of pigments accumulated during growth under low pO2. One-point, two-point, three-point, and ratio test crosses were performed between various mutant strains, and the results were amenable to conventional genetic analyses. A mapping function was found that related cotransfer frequency to map distance. Seven clusters of mutations, five affecting carotenoid and two affecting bacteriochlorophyll biosynthesis, were arranged in one linkage group. Each cluster of mutations is thought to represent a gene. The length of the mapped region is estimated to be less than 1% of the genome. Cotransfer is observed between markers separated by about 5 to 10 genes.