ENZYMES AS RIVER POLLUTANTS AND THE RESPONSE OF NATIVE EPILITHIC EXTRACELLULAR-ENZYME ACTIVITY

Extracellular-enzyme activity was measured in three watercourses, in N orth East England, which received effluent from sewage-works. Beta-D-g lucosidase, leucine-aminopeptidase and phosphatase activities were mar kedly elevated in water downstream of outfalls. Despite subsequent dow nstream decrease, elevated activities persisted over several kilometre s. Thus the effluents not only increased the quantity of organic matte r in the rivers, they also increased enzymatic hydrolysis of polymeric compounds, thus increasing the supply of low-molecular-weight moietie s available for microbial uptake and hence facilitating biopurificatio n. Partitioning of river water, by 0.2 mum filtration, showed that fre e-enzyme activity was important as well as cell and particle-associate d activity. Extracellular-enzyme activity was measured on stones from the bed of one watercourse. There was no evidence of end-product repre ssion of native epilithic enzyme activity, even though enzyme activity in surrounding water was very high. Instead, beta-D-glucosidase and p hosphatase activity increased on stones downstream of the outfall, and this was accompanied by an increase in the percentage of culturable e pilithic bacteria capable of synthesizing extracellular beta-D-glucosi dase and phosphatase.