Beta-Galactosidase activity of Escherichia coli under long-term starvation, alterations in temperature, and different nutrient conditions in lake water

ABSTRACT

beta-Galactosidase activity of Escherichia coli was investigated in response to long-term starvation, changes in temperature and the presence of certain nutrient sources in lake water. beta-Galactosidase activity decreased markedly in filtered-autoclaved lake water at 25 degrees C and 37 degrees C, whereas it remained almost constant at 4 degrees C and 15 degrees C for 60 days. Increases in beta-galactosidase activity were observed in response to the following nutrient sources glycine, serine, methionine and ammonium sulfate at 4 degrees C; glycine and ammonium sulfate at 15 degrees C; glycine, serine, methionine and ammonium sulfate at 30 degrees C. Glycine addition led to an increase in beta-galactosidase activity of almost five and seven orders of magnitude at 15 degrees C and 30 degrees C, respectively. In addition, L-methionine had the strongest influence on beta-galactosidase activity, which was detected as an increase of seven and eleven orders of magnitude at 4 degrees C and 30 degrees C, respectively. The effect of several amino acids and other nitrogen sources depended on the concentration of the nutrient source and the temperature. The results showed that, in lake water, long-term starvation, temperature change, and variations in nitrogen sources alter beta-galactosidase activity. Those effects should be taken into account when monitoring coliforms from the environment (AU)

RESUMEN

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