Toxicity measurements using fluorogenic compounds

Toxicity testing using fluorogenic compounds offers a number of advantages. These include a small sample volume, low cost, rapidity, and applicability to both a micro-organism monoculture and a biocenosis. The method relies on measuring the rate of enzymatic intracellular conversion of a fluorogenic substrate into a fluorochrome. We show how the rate of conversion depends on the substrate concentration, the biomass concentration and pH. We also show how the method can be used to measure the toxicities of several different toxicants, to study antagonistic and synergistic effects of different metal combinations and to study inhibition mechanisms. We then show that it is also possible to measure the cytoplasmic viscosity by exciting the fluorescein molecules in the cytoplasm with polarized light and measuring the polarization of the emitted fluorescence.