Regulation of beta- and alpha-glycolytic activities in the sediments of a eutrophic lake

Temporal changes in alpha- and beta -glucosidase activities, dissolved orga nic matter content, and bacterial biomass were studied in the superficial s ediment layer of a eutrophic lake during the period of anoxia. The mean alp ha- and beta -glucosidase activities were 30.7 +/- 11.0 and 15.1 +/- 6.2 nm ol h(-1) g(-1) of dry sediment, respectively. The specific beta -glucosidas e activity seemed to be stimulated by carbohydrates (r = 0.80, P < 0.05), w hereas the specifc <alpha>-glucosidase activity was negatively correlated w ith the dissolved protein concentration (r = -0.72, P < 0.10). To test the effect of organic matter on hydrolytic activities under controlled conditio ns, changes in specifc activities were studied in relation to the concentra tions of different types of organic matter: phytoplankton, polymers (protei ns, cellobiose, and starch) and monomers (glucose and amino acids). The spe cifc <alpha>- and beta -glucosidase activities were strongly induced by the ir natural substrates (starch and cellobiose, respectively) (P < 0.05) and were not inhibited by glucose. Proteins inhibited these activities (P < 0.0 5), whereas supplementation with amino acids had no effect on specifc glyco lytic activities.