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J. Bacteriol. doi:10.1128/JB.01210-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Defects in error prevention GO system potentiate stationary-phase-mutagenesis in Bacillus subtilis

Department of Biology, University of Guanajuato, P.O. Box 187, Guanajuato, Gto. 36050 MEXICO; School of Life Sciences, University of Nevada - Las Vegas, 4505 Maryland Parkway, Box 454004, Las Vegas, NV 89154-4004 USA

^* To whom correspondence should be addressed. Email: pedrama{at}quijote.ugto.mx.

	Abstract

Previous studies showed that a B. subtilis strain deficient in mismatch repair (encoded by the mutSL operon) promoted the production of stationary-phase induced mutations. However, overexpression of the mutSL operon did not completely suppress this process suggesting that additional DNA repair mechanisms are involved in the generation of stationary-phase-associated mutants in this bacterium. In agreement with this hypothesis, results presented in this work revealed that starved B. subtilis cells lacking a functional error prevention GO (8-oxo-G) system (composed by YtkD, MutM and YfhQ) had a dramatic propensity to increase the number of stationary-phase-induced revertants. These results strongly suggest that the occurrence of mutations is exacerbated by reactive oxygen species (ROS) in non-dividing cells of B. subtilis having an inactive GO system. Interestingly, overexpression of the mismatch repair system (MMR) significantly diminished the accumulation of mutations in cells deficient in the GO repair system during stationary phase. These results suggest that the MMR system plays a general role in correcting base mispairing induced by oxidative stress during stationary phase. Thus, the absence or depression of both the MMR and GO systems contributes to the production of stationary-phase mutants in B. subtilis. In conclusion, our results support the idea that oxidative stress is a mechanism that generates genetic diversity in starved cells of B. subtilis promoting stationary-phase induced mutagenesis in this soil microorganism.