Cloning and sequencing the recA+ genes of Acetobacter polyoxogenes and Acetobacter aceti: construction of recA- mutants of by transformation-mediated gene replacement.

The recA+ gene of Acetobacter polyoxogenes was cloned as a gene that conferred methyl methanesulfonate resistance (MMSR) on the RecA- Escherichia coli HB101. The cloned recA+ gene also conferred (i) resistance to UV irradiation, (ii) enhanced intrachromosomal recombination, and (iii) permitted prophage phi 80 induction in E. coli recA- lysogens. Nucleotide sequence determination revealed that the recA product consists of 348 amino acids (aa) corresponding to 38 kDa, and shows significant similarity to RecA proteins from other Gram- bacteria. Next, a portion of recA from Acetobacter aceti was cloned by using polymerase chain reaction with oligodeoxyribonucleotide primers design based on the A. polyoxogenes recA sequence. Due to availability of efficient host-vector and transformation systems in A. aceti, recA mutants of A. aceti were obtained by transformation-mediated gene replacement with the cloned A. aceti recA gene which was inactivated by insertion of the kanamycin-resistance-encoding gene from pACYC177. The recA mutants obtained in this way showed similar phenotypes to those of E. coli recA strains, such as increased sensitivity to MMS and to UV irradiation, and decreased homologous recombination.