A GENETIC AND MOLECULAR CHARACTERIZATION OF THE RECA GENE FROM STAPHYLOCOCCUS-AUREUS

Previous studies have identified mutant strains of Staphylococcus aure us that have deficiencies in genetic recombination and DNA repair. Alt hough these phenotypes were tentatively attributed to mutations within the S. aureus recA gene, experimental evidence to confirm this has ne ver been reported. To characterize recA from S. aureus, we first isola ted transposon insertion mutations that were in close proximity to the rec-A-like mutation (uvs-568) in strain 112 UVS-1. This allowed for t he mobilization of the uvs-568 mutation into strain RN4220. the common laboratory strain of S. aureus. Next, using Bacillus subtilis recA as a probe, we cloned S. aureus recA and determined its nucleotide seque nce. The deduced amino acid (aa) sequence of RecA contained 347 aa and was 74% identical to B. subtilis RecA. Using a cloned DNA fragment or iginating from within S. aureus recA, we then constructed a recA null mutant strain, designated KB103, which exhibited the same phenotypic c haracteristics imposed by the uvs-568 mutation in the same background. Furthermore, genetic and physical mapping of S. aureus recA placed it in the same region as the uvs-568 mutation. These data strongly sugge st that these mutations represent different alleles of the same recA g ene.