PMID:16824196

Citation	Sakai, A, Nakanishi, M, Yoshiyama, K and Maki, H (2006) Impact of reactive oxygen species on spontaneous mutagenesis in Escherichia coli.Genes Cells 11:767-78
Abstract	Reactive oxygen species (ROS) are potent oxidants that attack chromosomal DNA and free nucleotides, leading to oxidative DNA damage that causes genetic alterations. To avoid the ROS-mediated mutagenesis, cells have elaborate mechanisms including powerful antioxidant components and repair pathways that eliminate oxidative DNA damage. Because of the effective anti-mutagenic functions, it has been unclear to what extent the ROS contribute to spontaneous mutagenesis. Here we show that a significant portion of spontaneous mutations is actually caused by the ROS in aerobically growing Escherichia coli cells. Using the rpsL gene as a mutational target sequence, we established an experimental procedure to analyze spontaneous mutations occurring under a strictly anaerobic condition. Strong mutator phenotypes of cells defective in both mutM and mutY genes or ones lacking mutT gene were completely suppressed under the anaerobic condition, indicative of an absence of hydroxyl radicals in the cells. From a series of analyses with wild-type E. coli cells grown under different redox conditions, it appeared that 89% of base substitutions were caused by the ROS, especially hydroxyl radicals, in cells growing in the atmosphere. The ROS-mediated spontaneous mutations included highly site-specific base substitutions, two types of randomly occurring transversions, G:C-->C:G and A:T-->T:A, and -1 frameshifts at non-iterated base sequences.
Links	PubMed Online version:10.1111/j.1365-2443.2006.00982.x
Keywords	Aerobiosis; Anaerobiosis; Base Sequence; Escherichia coli; Escherichia coli Proteins; Hydrogen Peroxide; Hydroxyl Radical; Molecular Sequence Data; Mutation; Reactive Oxygen Species; Ribosomal Proteins
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Materials and Methods Used

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Phenotype Annotations

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Phenotype of	Taxon Information	Genotype Information (if known)	Condition Information	OMP ID	OMP Term Name	ECO ID	ECO Term Name	Notes	Status
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: MK6168 NCBI Taxon ID: 83333	Genotype of Reference Strain: fur+ Genotype of Experimental Strain : fur(del)::kan	Reference Condition:	OMP:0005068	increased mutation frequency			Figure 4: aerobic growth conditions. MK6168 = MK811 fur(del)::kan The fur(del)::kan allele was transduced from QC1732.
a single strain under different conditions	Taxon: Escherichia coli Strain: K-12 Substrain: MK811 NCBI Taxon ID: 83333	Genotype of Reference Strain:	Reference Condition: aerobic Experimental Condition: anaerobic	OMP:0005069	decreased mutation frequency			Figure 1: decreased frequency of base substitution mutations MK811 = MG1655 cysE::rpsL (735 bp DNA fragment containing rpsL+)
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