Characterization of spontaneous mutation in the oxyR strain of Escherichia coli.
Escherichia coli K-12 strain EY5, deficient in oxyR, was constructed to assess the role of oxyR and oxyR-regulated regulon in spontaneous mutagenesis. Mutagenesis was monitored by selecting two forward mutations of colicin B-sensitive to resistance and valine-sensitive to resistance, one base substitution mutation of rifampicin-sensitive to resistance and one reversion of argE3 his-4 to Arg(+) His(+). Deficiency of oxyR did not lead to the enhancement of spontaneous mutation frequencies of the four markers tested. By DNA sequence analysis, we determined 49 colicin B-resistant mutants derived from EY5 and found that 37% were base substitutions, 29% IS element insertions, 20% deletions, and 14% single base frameshifts. Among the base substitutions, G:C-->T:A transversions predominated followed by G:C-->A:T transitions and A:T-->T:A transversions. These spectra were essentially the same as those from oxyR(+) strains. The results indicate that oxyR and oxyR-regulated genes do not play a significant role in the defense against spontaneous mutagenesis.
Yamamura
E
E
Biological Institute, Sendai, 980-8578, Japan.
Nunoshiba
T
T
Kawata
M
M
Yamamoto
K
K
D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D016368:Frameshift Mutation; D005838:Genotype; D008565:Membrane Proteins / Q000235:genetics*; D009154:Mutation; D020125:Mutation, Missense; D018085:Regulon; D012097:Repressor Proteins / Q000235:genetics*; D017384:Sequence Deletion; D014157:Transcription Factors / Q000235:genetics*
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C499299:oxyR protein, E coli; C057616:tonB protein, Bacteria; C489181:tonB protein, E coli