CLONING, SEQUENCING, AND CHARACTERIZATION OF THE RECA GENE FROM RHODOPSEUDOMONAS-VIRIDIS AND CONSTRUCTION OF A RECA STRAIN

A recombination-deficient strain of the phototrophic bacterium Rhodops eudomonas viridis was constructed for the homologous expression of mod ified photosynthetic reaction center genes. The R. viridis recA gene w as cloned and subsequently deleted from the R. viridis genome. The clo ned R. viridis recA gene shows high identity to known recA genes and w as able to complement the Rec(-) phenotype of a Rhizobium meliloti rec A strain. The constructed R. viridis recA strain showed the general Re c(-) phenotype, i.e., increased sensitivity to DNA damage and severely impaired recombination ability. The latter property of this strain wi ll be of advantage in particular for expression of modified, nonfuncti onal photosynthetic reaction centers which are not as yet available.