Collection of Salmonella typhimurium strains for genotoxicologic and anti-genotoxicologic evaluation
Abstract
Homologous recombination is a DNA repair mechanism that additionally generates a biological diversity. Most of our knowledge about it was obtained from assays that used double strand ends as initiators of recombination. The present work is aimed at evaluating homologous recombination in bacteria, using an assay based on the segregation of chromosomal duplication. This assay measures exchanges between sister strands without favoring any pathway. A collection of strains of Salmonella enterica serovar typhimurium deficient in genes coding for proteins involved in homologous recombination was built. We evaluated spontaneous (SSR) and UV-induced segregation rate (UV-ISR). We demonstrated that the absence of RuvC resolvase did not affect SSR, while defects in RecA, RecQ and RecB/RecF decreased it and the lack of SbcCD or RuvAB stimulated it. In RecB null mutants, lesions that are not commonly sensed by RecFOR seem to have been recognized and repaired by this pathway. The methodology supported the corroboration of a RecA-independent pathway in Salmonella and suggests the existence of alternative recombination pathways in recB/recF double mutants.
