On the metabolic radioprotection.

The effect of different factors (0.025 mol/l of cysteine, 0.0003 mol/l of iodoacetamide, 0.328 mol/l of hydroxyurea, deprivation of glucose or essential amino acid and uracil from the medium) on the resistance to gamma rays was studied in the cells of E. coli TAU- during the logarithmic phase. The resistance to gamma rays was also investigated during the stationary phase. It was established that treatments, including reversible inhibition of cell division and unbalance of macromolecular synthesis of a type in which the DNA synthesis was continued without a simultaneous RNA- and protein synthesis enhanced the radioresistance. This type of asynchrony of macromolecular synthesis could increase radioresistance by promotion of repair processes of single-strand breaks in DNA after a single dose of 15 krads irradiation. For this latter studies E. coli K12 (AB 2497) strain and the technique developed by McGrath and Williams was used.