NONRECIPROCAL REGULATION OF RHODOBACTER-CAPSULATUS AND RHODOBACTER-SPHAEROIDES RECA GENES EXPRESSION

The Rhodobacter capsulatus recA gene has been isolated and sequenced. Its deduced amino acid sequence showed the closest identity with the R hodobacter sphaeroides RecA protein (91% identity). However, the promo ter regions of both R. capsulatus and R. sphaeroides recA genes are on ly 64% similar. An Escherichia coli-like LexA binding site was not pre sent in the upstream region of the R. capsulatus recA gene. Neverthele ss, the R. capsulatus recA gene is inducible by DNA damage in both het ero- and phototrophically growing conditions. The R. capsulatus recA g ene is poorly induced when inserted into the chromosome of R. sphaeroi des, indicating that the recA gene of both bacteria possess different control sequences despite their phylogenetically close relationship.