title: Role of Bacillus subtilis DNA Glycosylase MutM in Counteracting Oxidatively Induced DNA Damage and in Stationary-Phase-Associated Mutagenesis.
abstract: Reactive oxygen species (ROS) promote the synthesis of the DNA lesion 8-oxo-G, whose mutagenic effects are counteracted in distinct organisms by the DNA glycosylase MutM. We report here that in Bacillus subtilis, mutM is expressed during the exponential and stationary phases of growth. In agreement with this expression pattern, results of a Western blot analysis confirmed the presence of MutM in both stages of growth. In comparison with cells of a wild-type strain, cells of B. subtilis lacking MutM increased their spontaneous mutation frequency to Rif(r) and were more sensitive to the ROS promoter agents hydrogen peroxide and 1,1'-dimethyl-4,4'-bipyridinium dichloride (Paraquat). However, despite MutM's proven participation in preventing ROS-induced-DNA damage, the expression of mutM was not induced by hydrogen peroxide, mitomycin C, or NaCl, suggesting that transcription of this gene is not under the control of the RecA, PerR, or σ(B) regulons. Finally, the role of MutM in stationary-phase-associated mutagenesis (SPM) was investigated in the strain B. subtilis YB955 (hisC952 metB5 leuC427). Results revealed that under limiting growth conditions, a mutM knockout strain significantly increased the amount of stationary-phase-associated his, met, and leu revertants produced. In summary, our results support the notion that the absence of MutM promotes mutagenesis that allows nutritionally stressed B. subtilis cells to escape from growth-limiting conditions.
  
  
  OBJECTIVE
  The present study describes the role played by a DNA repair protein (MutM) in protecting the soil bacterium Bacillus subtilis from the genotoxic effects induced by reactive oxygen species (ROS) promoter agents. Moreover, it reveals that the genetic inactivation of mutM allows nutritionally stressed bacteria to escape from growth-limiting conditions, putatively by a mechanism that involves the accumulation and error-prone processing of oxidized DNA bases.
authors.affiliation: Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, Guanajuato, Mexico.
authors.forename: Martha
authors.initials: M
authors.lastname: Gómez-Marroquín
authors.affiliation: Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, Guanajuato, Mexico.
authors.forename: Luz E
authors.initials: LE
authors.lastname: Vidales
authors.affiliation: Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, Guanajuato, Mexico.
authors.forename: Bernardo N
authors.initials: BN
authors.lastname: Debora
authors.affiliation: Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, Guanajuato, Mexico.
authors.forename: Fernando
authors.initials: F
authors.lastname: Santos-Escobar
authors.affiliation: Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, Guanajuato, Mexico.
authors.forename: Armando
authors.initials: A
authors.lastname: Obregón-Herrera
authors.affiliation: School of Life Sciences, University of Nevada, Las Vegas, Nevada, USA.
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Robleto
authors.affiliation: Department of Biology, Division of Natural and Exact Sciences, University of Guanajuato, Guanajuato, Mexico pedrama@ugto.mx.
authors.forename: Mario
authors.initials: M
authors.lastname: Pedraza-Reyes
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D045647:DNA Glycosylases / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D016296:Mutagenesis; D018384:Oxidative Stress; D013312:Stress, Physiological
chemical_list: D001426:Bacterial Proteins; D045647:DNA Glycosylases
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