The ability of membrane potential dyes and calcafluor white to distinguish between viable and non-viable bacteria


Professor David Lloyd, School of Pure and Applied Biology, University of Wales College of Cardiff, PO Box 915, Cardiff CF1 3TL, UK.


Various dyes were assessed for their ability to discriminate between viable and non-viable bacteria. Two methods of killing were employed: by heat treatment or by gramicidin treatment. Staining was carried out in two ways; by staining directly in the medium or by washing cells prior to staining in buffer. Carbocyanine and rhodamine 123 dyes only exhibited small changes in fluorescence between viable and non-viable populations of bacteria. Both oxonol dye (bis 1,3-dibutylbarbituric acid trimethine oxonol) and calcafluor white proved much more useful.