The experimental showing, that reactivation viability phenomenon of E. coli B/r bacteria in phosphate buffer takes place only after irradiation under certain dose range of 60Co gamma-ray, induced the death of certain part of viable cell bacteria population, are presented. It was illustrated that intensity of reactivation viability phenomenon of bacteria do not depend on the concentration of viable microorganisms and the presence in suspension medium nutrient material, leaved of irradiated cells. The received data shown that in the base of the phenomenon there are the processes, distinguished from processes of usual cell reproduction, and may be the consequence of radiostimulate influence on the cell physiology, known from literature, as hormesis.