RESEARCH ON THE HETEROGENEITY OF A MICROCOCCUS-LUTEUS CULTURE DURING AN EXTENDED STATIONARY-PHASE - SUBPOPULATION SEPARATION AND CHARACTERIZATION

After prolonged starvation, a population of stationary-phase Micrococc us luteus cells (containing dormant cells, as shown earlier) was inves tigated using a flow cytometer and the method of distributing cells in a two-phase system composed of aqueous solutions of polymers. Flow cy tometry revealed the existence of two cell subpopulations distinguishe d by their ability to bind the fluorescent probe rhodamine 123. In the two-phase system, the two subpopulations were located in the polyethy lene glycol (PEG) phase at the interface. The cell subpopulation with enhanced fluorescence, isolated with a cell sorter, contained viable ( colony-forming) cells and dormant cells which could be resuscitated. M ost viable cells stayed in the PEG fraction. Electron microscopy showe d that the PEG fraction predominantly contained intact cells.