VIABILITY ASSESSMENT OF BACTERIA IN MIXED POPULATIONS USING FLOW-CYTOMETRY

In microbiology cells are called viable when they can be shown to prol iferate. Due to long lag phases and the cells' sensitivity to the cond itions around them, this definition presents problems when investigati ng stressed or injured cells. Colony counts only show reproduction, wh ilst direct single-cell investigation can divide the status of cells i nto four stages: (i) reproductive viable cells, (ii) vital cells, (iii ) intact cells and (iv) dead cells. Multicolour staining now cytometry has been found to provide a powerful method for investigating these v arious states of viability. This is illustrated with examples with som e emphasis on mixed bacterial populations.