Direct Measurements of Natural Planktonic Bacterial Community Viability by Flow Cytometry

A range of fluorescent viability dyes were used in conjunction with flow cytometry to rapidly enumerate viable bacteria from freshwater environments. Optimal labelling was achieved by using carboxyfluorescein diacetate or chemchrome B with a detergent-mediated permeabilization step. The viable bacterial count under optimal conditions was 7% in oligotrophic lake water and 75% in polluted river water.