Dividing subpopulation of Escherichia coli in stationary phase.

The bacterial growth cycle contains different phases: after the growth substrate is exhausted or the toxic waste products accumulate the growth stops. In this non-growing culture the number of colony forming bacteria remains constant or starts to decrease. It has been shown that during prolonged incubation there is constant growth and death of bacteria and certain mutant populations take over the culture. Here we show that the dynamic cell division and death balance can be obtained even before the appearance of mutants. The possible presence of different subpopulation should be considered when analyzing physiological states of bacterial cultures.