Increased Resistance to Ionizing and Ultraviolet Radiation in Escherichia coliJM83 Is Associated with a Chromosomal Rearrangement

摘要

Cells cope with radiation damage through several mechanisms: (1) increased DNArepair activity, (2) scavenging and inactivation of radiation-induced radical molecules, and (3) entry into a Go-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 pheno-type 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