Drinking water is rich in microbial life

Flow cytometry (FCM) studies have been used for the quantification of microbial cells in drinking water. A recent study has shown that drinking water contains100 to 10,000 times more living cells than the conventional plate count method would suggest.

The microbial content of water is normally assessed using the heterotrophic plate count (HPC). The HPC method involves growing any bacteria present in a sample of water onto solid nutrient media (incubated at a warm temperature), and the colonies formed are then counted.

The weakness with the HPC method are the incubation time and the fact that only a fraction of the living cells actually present in samples are counted (the so-termed ‘viable but non-culturable’ microorganisms).

The utilisation of FCM methodology can be used to determine, more accurately, the total cell count in a water sample within a matter of minutes.

FCM works by staining any cells contained in a sample 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. The resultant scatter and fluorescence signals are picked up by detectors, and analytical software is used to classify each individual particle (cell).

To read more about this technology and the associated research, visit EAWAG: Swiss Federal Institute of Aquatic Scienceand Technology.

Posted by Tim Sandle