[Survival of Escherichia coli cells during storage in suspensions of varying concentrations]

The presence of positive correlative connection between death rate of Escherichia coli M-17 cells and the density of their suspension have been estimated. It has been shown, that the accumulation in extracellular medium (ECM) of death-stimulating (DS) metabolites, the concentration of which was higher in the suspensions of higher densities, was the immediate cause of the acceleration of death in suspensions with densities higher than 1 x 10(9) cells/ml. DS metabolites could be removed from ECM by adsorption or dialysis, and, thus, they had comparably low molecular mass. The presence of DS metabolites led to the acceleration of death of test-cultures E. coli M-17. The filtrates of ECM of suspensions with density lower than 1 x 10(9) cells/ml did not accelerate the death rate of test-cultures, and, most probably, did not contain any DS-substances. It is supposed, that the role of DS-substances is the maintenance of optimal size of the population of bacteria. The low effective concentrations of these substances make it possible to consider that their functions are nothing but regulatory.