Drinking water unexpectedly rich in microbial life

FCM, short for‘flow cytometry’is a new analytical method for the quantification of microbial cells in drinking water. Developed at Swiss Federal Institute of Aquatic Science and Technology, the method provides much more realistic results than the conventional microbiological tests. In flow cytometry, the cells in a sample are first stained with fluorescent dyes, which bind to DNA. The cells are then passed in single file through a glass capillary, where they are exposed to a beam of light from a laser. Detectors pick up the resulting scatter and fluorescence signals, and analytical software is used to classify each individual particle. The results demonstrate that even good-quality drinking water harbours 100 to 10,000 times more living cells than the conventional plate count method would suggest.