Lambda-prophage induction in repair-deficient and wild type E. coli strains by gamma-rays and heavy ions.

Lambda-prophage induction in repair-deficient and wild-type E. coli strains by heavy ions and gamma-rays has been investigated. The dose dependence of the fraction of induced cells has been measured and its initial slope (lambda-induction potency) determined. The induction by gamma-rays was found to be more efficient in a polA-repair-deficient strain; the value of lambda-induction potency is zero in lexA- and recA- strains. The lambda-induction potency increased with LET for wild-type cells but remained constant in the case of polA- mutant cells. It is suggested that the DNA damage triggering the lambda-prophage induction in the case of ionizing radiation could be a type of DNA single-strand break with complex structure which cannot be repaired by fast repair processes, and which requires a substantial level of energy deposition for induction in a DNA molecule.

[The modifying effect of glycerine and cysteamine on prophage lambda induction in E. coli cells under gamma irradiation]. / Modifitsiruiushchee vliianie glitserina i tsisteamina na induktsiiu profaga lambda u kletok E. coli pri gamma-obluchenii.

In studying the modifying influence of glycerol and cysteamine of gamma radiation induction of lambda prophage it was shown that dose curves for lambda prophage induced upon irradiation in normal conditions and in the presence of glycerol are those with a maximum. In the presence of cysteamine, the prophage induction is inhibited significantly.

[The effect of genotype on the induction of prophage lambda in E. coli cells by ionizing radiation of various LET]. / Vliianie genotipa na induktsiiu profaga lambda u kletok E. coli ionisiruirshdhimi izlucheniiami s raznoi LPE.

A study was made of the influence of the repair genotype on lambda prophage induction by ionizing radiation of different LET in lysogenic E. coli cells. Bacterial strains W3110, P3478, GC244, and 30SO were exposed to gamma-rays and helium ions of 22 keV/microns. Induction of the prophage in GC244 and 30SO strains deficient by lexA and recA genes was either inhibited (GC244) or lacking (30SO). Inducibility of P3478 carrying polA mutation was 12 and 5 times as high as that of the wild type strain after exposure to gamma-radiation and helium ions, respectively.

[The role of sensitive bacteria in determining the count of phage negative colonies on solid growth media]. / Rol' chuvstvitel'nykh bakterii v opredelenii chisla negativnykh kolonii faga na plotnykh pitatel'nykh sredakh.

The purpose of the work was to study how the number of phage negative colonies on a solid growth medium depended on the concentration of a sensitive bacterial strain. For the system of phage lambda and a sensitive E. coli cell, the number of negative colonies was maximal at a concentration of ca. 4 X 10(8) cells/ml.