*Strahlenbiologisches Institut der Universitat München, 8 München 2, Bavariaring 19, W. Germany.
PROTECTION OF ESCHERICHIA COLI CELLS AGAINST THE LETHAL EFFECTS OF ULTRAVIOLET AND X IRRADIATION BY PRIOR X IRRADIATION: A GENETIC AND PHYSIOLOGICAL STUDY
Article first published online: 2 JAN 2008
Photochemistry and Photobiology
Volume 24, Issue 6, pages 515–523, December 1976
How to Cite
Smith, K. C. and Martignoni, K. D. (1976), PROTECTION OF ESCHERICHIA COLI CELLS AGAINST THE LETHAL EFFECTS OF ULTRAVIOLET AND X IRRADIATION BY PRIOR X IRRADIATION: A GENETIC AND PHYSIOLOGICAL STUDY. Photochemistry and Photobiology, 24: 515–523. doi: 10.1111/j.1751-1097.1976.tb06868.x
- Issue published online: 2 JAN 2008
- Article first published online: 2 JAN 2008
- Received 1 April 1976; accepted 21 June 1976
Abstract— When log phase cells of wild-type E. coli K-12 were maintained in growth medium after X irradiation, they became progressively more resistant to a subsequent exposure to UV or X radiation. The time to achieve maximum resistance was about 60 min. The uvrB, uvrD, polA and certain exrA strains (W3110 background) also demonstrated this X ray-induced resistance to subsequent UV or X irradiation but recA, recB, lex (AB1157 or W3110 backgrounds) and other exrA strains (AB1157 background) did not. The resistance induced in wild-type, uvrB and uvrD cells was characterized by the production or enhancement of a shoulder on the survival curves obtained for the second irradiation, while the resistance induced in the W3110 exrA strains was expressed only as a change in slope. The induction of resistance in the W3110 exrA strain was not inhibited by the presence of chloramphenicol, but that in the wild-type cells appeared to be. The production or enhancement of a shoulder on the survival curves of the rec+lex+exr+ cells is consistent with the concept of the radiation induction of repair enzymes. Alternative explanations, however, are discussed.