Regulation of β- and α-glycolytic activities in the sediments of a eutrophic lake

Temporal changes in alpha- and beta -glucosidase activities, dissolved organic matter content, and bacterial biomass were studied in the superficial sediment layer of a eutrophic lake during the period of anoxia. The mean alpha- and beta -glucosidase activities were 30.7 +/- 11.0 and 15.1 +/- 6.2 nmol h(-1) g(-1) of dry sediment, respectively. The specific beta -glucosidase activity seemed to be stimulated by carbohydrates (r = 0.80, P < 0.05), whereas the specifc <alpha>-glucosidase activity was negatively correlated with the dissolved protein concentration (r = -0.72, P < 0.10). To test the effect of organic matter on hydrolytic activities under controlled conditions, changes in specifc activities were studied in relation to the concentrations of different types of organic matter: phytoplankton, polymers (proteins, cellobiose, and starch) and monomers (glucose and amino acids). The specifc <alpha>- and beta -glucosidase activities were strongly induced by their natural substrates (starch and cellobiose, respectively) (P < 0.05) and were not inhibited by glucose. Proteins inhibited these activities (P < 0.05), whereas supplementation with amino acids had no effect on specifc glycolytic activities.