Direct differential counting compared with testing of isolates as means of assessing hydrolytic capacities of natural microbial populations.

The abundance of microorganisms with characteristic, physiological activities in aquatic sediment communities can be estimated either by direct differential counting on selective media or by making isolations followed by testing of the isolates. The two methods have been compared with regard to microorganisms performing hydrolyses of different compounds. The first method was used to examine the effect of a model ecocontaminant on the hydrolytic activities of the sediment population.