Spontaneous and UV-induced mutations in Escherichia coli K-12 strains with altered or absent DNA polymerase I

Journal Article · Mon May 01 00:00:00 EDT 1989 · J. Bacteriol.; (United States)

OSTI ID:5901826

Bates, H; Randall, S K; Rayssiguier, C; Bridges, B A; Goodman, M F; Radman, M

The induction of mutations to valine resistance and to rifampin resistance occurs after UV irradiation in bacteria carrying a deletion through the polA gene (delta polA), showing that DNA polymerase I (PolI) is not an essential enzyme for this process. The PolI deletion strain showed a 7- to 10-fold-higher spontaneous mutation frequency than the wild type. The presence in the deletion strain of the 5'----3' exonuclease fragment on an F' episome caused an additional 10-fold increase in spontaneous mutation frequency, resulting in mutation frequencies on the order of 50- to 100-fold greater than wild type. The mutator effect associated with the 5'----3' exonuclease gene fragment together with much of the effect attributable to the polA deletion was blocked in bacteria carrying a umuC mutation. The mutator activity therefore appears to reflect constitutive SOS induction. Excision-proficient polA deletion strains exhibited increased sensitivity to the lethal effect of UV light which was only partially ameliorated by the presence of polA+ on an F' episome. The UV-induced mutation rate to rifampin resistance was marginally lower in delta polA bacteria than in bacteria carrying the polA+ allele. This effect is unlikely to be caused by the existence of a PolI-dependent mutagenic pathway and is probably an indirect effect caused by an alteration in the pattern of excision repair, since it did not occur in excision-deficient (uvrA) bacteria.

• Research Organization: Univ. of Sussex, Brighton (England)
• OSTI ID: 5901826
• Journal Information: J. Bacteriol.; (United States), Vol. 171:5
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
DNA POLYMERASES
BIOLOGICAL FUNCTIONS
ESCHERICHIA COLI
RADIOSENSITIVITY
DNA REPAIR
GENETIC RADIATION EFFECTS
MUTATION FREQUENCY
SPONTANEOUS MUTATIONS
ULTRAVIOLET RADIATION
VALINE
AMINO ACIDS
BACTERIA
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CARBOXYLIC ACIDS
ELECTROMAGNETIC RADIATION
ENZYMES
FUNCTIONS
GENETIC EFFECTS
MICROORGANISMS
MUTATIONS
NUCLEOTIDYLTRANSFERASES
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHOSPHORUS-GROUP TRANSFERASES
POLYMERASES
RADIATION EFFECTS
RADIATIONS
RECOVERY
REPAIR
TRANSFERASES
560130* - Radiation Effects on Microorganisms