title: Induction of the homologous recombination system by hexavalent chromium in Rhizobium etli.
abstract: Induction of homologous recombination in Rhizobium etli to repair the DNA damage caused by hexavalent chromium (Cr) was evaluated. Mutants in recombination genes such as addA, recF, recA, ruvB, recG, and a double mutant ruvBrecG showed different sensitivity levels to Cr. As expected, the recA mutant showed the highest susceptibility, while complementation restored the Cr-resistant phenotype, similar to the wild-type strain. Small plasmid recombination increased up to 30-fold in the presence of Cr (0.05 mM) in the wild-type strain, while no change was observed in the recA mutant. A 20-fold increase in small plasmid recombination was also observed in the addA mutant in the presence of Cr. In addition, the ruvB mutant showed similar increases with Cr exposure to the wild-type strain, suggesting that other genetic elements may substitute its important role during recombination. Interestingly, continuous Cr exposure (0.05 mM) clearly induced the genetic expression of addA, recA, and ruvB genes. Finally, recombination mutants also showed susceptibility to other DNA-damaging agents such as tellurite and selenite. Together, these results confirm the induction and significance of the R. etli homologous recombination system to repair DNA damage caused by hexavalent Cr.
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, Mexico. Electronic address: gsantoyo@umich.mx.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Santoyo
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, Mexico.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Orozco-Mosqueda
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, Mexico.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Valdez-Martínez
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, Mexico.
authors.forename: Ma Del Carmen
authors.initials: Mdel C
authors.lastname: Orozco-Mosqueda
mesh_terms: D002857:Chromium / Q000494:pharmacology* / Q000633:toxicity; D004249:DNA Damage; D004260:DNA Repair; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D059765:Homologous Recombination / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D008954:Models, Biological; D042163:Rhizobium etli / Q000187:drug effects* / Q000235:genetics*; D012643:Selenium / Q000494:pharmacology; D013691:Tellurium / Q000494:pharmacology
chemical_list: D002857:Chromium; C074702:chromium hexavalent ion; D012643:Selenium; D013691:Tellurium
keywords: Hexavalent chromium; Homologous recombination; Rhizobium etli