A Locus That Controls Filament Formation and Sensitivity to Radiation in Escherichia Coli K-12

Long form radiosensitive mutants were selected from among the progeny of survivors of an ultraviolet irradiated parental strain of E. coli K-12 by their mucoid appearance on supplemented minimal agar. The parental strain was F/sup -/ and carried various auxotrophic markers. Crosses with Hfr strains revealed that all the long-form cells carried a mutation at a locus designated lon, which is situated between lac and gal, close to T6. The parental lon/sup +/ strain resembles B/r in survival following x or uv irradiation, while lon mutants are relatively sensitive and are similar to strain B. The greater radiosensitivity of the lon mutants is not due to the loss of the capacity to reactivate uv- photoproducts in DNA because equal numbers of plaques are found when uv irradiated Tl phage is plated on lon and lon/sup +/ strains. (auth)