Staining procedures for flow cytometric monitoring of bacterial populations

Dual or multiple parameter flow cytometric analysis is developing into a powerful method for characterizing microbial populations. The distinguishing of the populations only by assignment of size/shape measurements by scattered ligth renders as not satisfactory. To differentiate between the cells, the employment of a specific fluorescence marker is absolutely necessary. Methods are presented for the flow cytometric determination of DNA and the polymer poly-β-hydroxybutyrate (PHB) content in three different bacterial strains. The measurement of the 3β-hydroxysterol content enables the differentation between yeast and bacterial organisms in mixed microbial populations. Monitoring the ratio of live to dead bacterial cells in soil or water samples, e.g. in pure culture systems, is shown.