Developing a biosensor for estrogens in water samples: study of the real-time response of live cells of the estrogen-sensitive yeast strain RMY/ER-ERE using fluorescence microscopy.

Using a fluorescein di-beta-D-galactopyranoside (FDG) substrate we show that in live cells of an estrogen-sensitive yeast strain RMY/ER-ERE with human estrogen receptor (ERalpha) gene and the lacZ gene which encodes beta-galactosidase, the uptake of 17beta-estradiol (E2) and the subsequent production of beta-galactosidase enzyme occur quite rapidly, with maximal enzyme-catalyzed product formation evident after about 30 min of exposure to E2. This finding which agrees with the well-known rates of enzyme-catalyzed reactions could have implications for shortening the duration of environmental sample screening and monitoring regimes using yeast-based estrogen assays, and the development of biosensors for environmental estrogens to complement quantification methods.