Genetic-physical mapping of a photosynthetic gene cluster from R. capsulata.

Transposon mutagenesis and complementation analysis of the photosynthesis genes in Rhodopseudomonas capsulata is presented utilizing Tn5.7 mutagenized R-primes. The R-prime pRPS404 contains many of the genes necessary for the differentiation of the photosynthetic apparatus. Utilizing homologous recombination, 30 independent copies of Tn5.7 were inserted into the R. capsulata chromosome with subsequent deletion of wild-type alleles. Mutants were characterized by absorption spectroscopy, SDS-PAGE, and determination of capability for photosynthetic growth. Many mutations in the bacteriochlorophyll and carotenoid biosynthetic pathways were isolated. A regulatory mutation was isolated affecting reaction-center synthesis as well as a 44 kd heme-containing polypeptide. Complementation analysis using various pRPR404::Tn5.7 plasmids has led to the postulation of transcriptional units.