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 Rhodopseudomonas viridis was constructed for the homologous expression of modified photosynthetic reaction center genes. The R. viridis recA gene was cloned and subsequently deleted from the R. viridis genome. The cloned R. viridis recA gene shows high identity to known recA genes and was able to complement the Rec⁻ phenotype of a Rhizobium meliloti recA strain. The constructed R. viridis recA strain showed the general Rec⁻ phenotype, i.e., increased sensitivity to DNA damage and severely impaired recombination ability. The latter property of this strain will be of advantage in particular for expression of modified, nonfunctional photosynthetic reaction centers which are not as yet available.