Characterization of spontaneous mutation in the ΔsoxR and SoxS overproducing strains of Escherichia coli

Eiji Yamamura, Eun Hye Lee, Akihiro Kuzumaki, Norio Uematsu, Tatsuo Nunoshiba, Masakado Kawata, Kazuo Yamamoto

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


To examine the role of the soxRS regulon in mutagenesis, we characterized the spontaneous mutations occurring in the endogenous tonB gene in the ΔsoxR strain and the SoxS overproducing strain of Escherichia coli. Neither the ΔsoxR strain nor the SoxS overproducing strain led to an enhancement or diminishment of the spontaneous mutation frequency. By DNA sequencing, we determined 50 spontaneous mutants from the ΔsoxR strains, and found that 36% were both base substitutions and IS insertions, 14% frameshifts and 10% deletions. Among the base substitutions, G:C→T:A transversions and G:C→A:T transitions predominated, followed by A:T→T:A transversions. We determined 54 spontaneous mutants from the SoxS overproducing strains, and found that 37% were IS insertions, 31% base substitutions, 17% frameshifts, 9% deletions and 6% duplications. Among the base substitutions, G:C→T:A transversions dominated, followed by A:T→T:A transversions and G:C→A:T transitions. These results were similar to those from the soxRS+ strains. Thus, it is suggested that the soxRS-regulated genes do not play a significant role in the defense against spontaneous mutagenesis.

Original languageEnglish
Pages (from-to)195-203
Number of pages9
JournalJournal of radiation research
Issue number2
Publication statusPublished - 2002 Jun


  • Reactive oxygen species
  • SoxRS
  • Spontaneous mutasenesis
  • TonB, E. coli

ASJC Scopus subject areas

  • Radiation
  • Radiology Nuclear Medicine and imaging
  • Health, Toxicology and Mutagenesis


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