DNA RECOMBINATION IN Escherichia coli AND Pseudomonas aeruginosa

MORO CAMILA; BORGOGNO MARÍA VICTORIA; MONTI MARIELA; ARGARAÑA CARLOS ENRIQUE

Córdoba

Congreso; LII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2016

RecA is a central factor in the recombination between DNA molecules containing perfect homology (homologous, HO) or very lowdivergence (homeologous, HE). Recombination of sequences containing low divergence is inhibited by the action of the mismatchrepair 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 thanHE recombination rates. The absence of MutS did not affect HO recombination, but raised HE recombination to values close to that ofHO recombination, indicating that MutS controls the exchange between divergent sequences. In theE. coliRecA-deficient strain, bothHO 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. Theseresults suggested the existence inP. aeruginosa, of an additional recombination system independent of RecA. At present, we areanalyzing the molecular structure of the recombinant products with the aim to elucidate this alternative mechanism.