Increased resistance to ionizing and ultraviolet radiation in Escherichia coli JM83 is associated with a chromosomal rearrangement.
Cells cope with radiation damage through several mechanisms: (1) increased DNA repair activity, (2) scavenging and inactivation of radiation-induced radical molecules, and (3) entry into a G0-like quiescent state. We have investigated a chromosomal rearrangement to elucidate further the molecular and genetic mechanisms underlying these phenomena. A mutant of Escherichia coli JM83 (phi 80dlacZ delta M15) was isolated that demonstrated significantly increased resistance to both ionizing and ultraviolet radiation. Surviving fractions of mutant and wild-type cells were measured following exposure to standardized doses of radiation. Increased radioresistance was directly related to a chromosomal alteration near the bacteriophage phi 80 attachment site (attB), as initially detected by the LacZ- phenotype of the isolate. Southern hybridization of chromosomal DNA from the mutant and wild-type E. coli JM83 strains indicated that a deletion had occurred. We propose that the deletion near the attB locus produces the radioresistant phenotype of the E. coli JM83 LacZ- mutant, perhaps through the alteration or inactivation of a gene or its controlling element(s).
McLean
K M
KM
Armed Forces Radiobiology Research Institute, Bethesda, Maryland 20889-5145.
Gutman
P D
PD
Minton
K W
KW
Clark
E P
EP
D002470:Cell Survival / Q000528:radiation effects; D002875:Chromosomes / Q000648:ultrastructure*; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics / Q000528:radiation effects*; D009154:Mutation; D011831:Radiation Genetics; D011836:Radiation Tolerance / Q000235:genetics*; D014466:Ultraviolet Rays