DNA recombination in Escherichia coli and Pseudomonas aeruginosa

CAMILA MORO; MARIA VICTORIA BORGOGNO; MARIELA R. MONTI; CARLOS E. ARGARAÑA

Córdoba

Congreso; LII Reunión Anual de SAIB; 2016

MI-P19DNA RECOMBINATION INEscherichia coliAND Pseudomonas aeruginosaMoro C, Borgogno MV, Monti MR, Argaraña CE.CIQUIBIC-CONICET, Dpto de Química Biológica, Fac de Cs Químicas, UNC. Córdoba, República Argentina.E-mail: camimoro17@gmail.comRecA is a central factor in the recombination between DNA molecules containing perfect homology (homologous, HO) or very low divergence (homeologous, HE). Recombination of sequences containing low divergence is inhibited by the action of the mismatch repair proteins MutS and MutL. We have built a genetic system to determine HO and HE recombination in Gram-negative bacteria. Using this system, we determined the recombination rate in the wild-type (WT) and mutant strains (recAandmutS) ofPseudomonasaeruginosaandEscherichiacoli. In both bacteria, HO recombination rates were approximately 60-200-fold higher than HE recombination rates. The absence of MutS did not affect HO recombination, but raised HE recombination to values close to that of HO recombination, indicating that MutS controls the exchange between divergent sequences. In theE. coliRecA-deficient strain, both HO and HE recombination rates were 60-fold lower than that obtained for the WT strain. TherecAdeletion mutant of P. aeruginosashowed that HO and HE recombination rates decreased 15 and 3-fold respectively, compared with the WT strain. These results suggested the existence inP. aeruginosa, of an additional recombination system independent of RecA. At present, we are analyzing the molecular structure of the recombinant products with the aim to elucidate this alternative mechanism.