Vigour, vitality and viability of microorganisms

Assessment of the vigour, vitality or viability of microorganisms must be done on an individual basis and thus requires the non-invasive interrogation of single organisms. For suspended organisms, flow cytometry provides a powerful means of measurement of a wide range of characteristics. Similar information for microbes in aggregates or growing on surfaces may be obtained by use of confocal scanning laser microscopy. For instance, membrane potential-sensitive fluorophores can distinguish between vigorous, frail and dead cells.