Measurements of microbial community activities in individual soil macroaggregates

The functional potential of single soil macroaggregates may provide insights into the localized distribution of microbial activities better than traditional assays conducted on bulk quantities of soil. Thus, we scaled down enzyme assays for beta-glucosidase, N-acetyl-beta-D-glucosaminidase, lipase, and leucine aminopeptidase to measure of the enzyme potential of individual macroaggregates (250-1000 mu m diameter). Across all enzymes, the smallest macroaggregates had the greatest activity and the range of enzyme activities observed in all macroaggregates supports the hypothesis that functional potential in soil may be distributed in a patchy fashion. Paired analyses of ATP as a surrogate for active microbial biomass and beta-glucosidase on the same macroaggregates suggest the presence of both extracellular beta-glucosidase functioning in macroaggregates with no detectable ATP and also of relatively active microbial communities (high ATP) that have low beta-glucosidase potentials. Studying function at a scale more consistent with microbial habitat presents greater opportunity to link microbial community structure to microbial community function. Published by Elsevier Ltd.