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Title: Measurements of microbial community activities in individual soil macroaggregates

item BAILEY, VANESSA - Pacific Northwest National Laboratory
item BILSKIS, CHRISTINA - Pacific Northwest National Laboratory
item FANSLER, SARAH - Pacific Northwest National Laboratory
item MCCUE, LEE ANN - Pacific Northwest National Laboratory
item Smith, Jeffrey
item KONOPKA, ALLEN - Pacific Northwest National Laboratory

Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2012
Publication Date: 1/19/2012
Citation: Bailey, V.L., Bilskis, C.L., Fansler, S.J., McCue, L., Smith, J.L., Konopka, A. 2012. Measurements of microbial community activities in individual soil macroaggregates. Soil Biology and Biochemistry. Volume 48, Pages 192–195.

Interpretive Summary: Nutrient cycling, such as nitrogen, in soils occurs mainly in small and medium size particles called aggregates. Traditional soil microbiology studies the microbial community and processes in gram- and larger quantities of soil. However, studying soil aggregates as discrete entities may better reflect soil as a habitat. Many studies have analyzed pools of aggregate size fractions and there has been some success reported in profiling those in individual aggregates. In this study we looked at microbial enzymes, which mediate nitrogen cycling, in individual aggregates of different sizes. We found that the smallest aggregates had the greatest enzyme activity. However the range of enzyme activity in all aggregates suggest that enzyme activity and nutrient cycling is distributed in a patchy fashion in soil. This research can be used by scientists interested in small scale nutrient cycling.

Technical Abstract: The functional potential of single soil aggregates 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 ß-glucosidase, N-acetyl-ß-D-glucosaminidase, lipase, and leucine aminopeptidase to measure of the enzyme potential of individual aggregates (250-1000 µm diameter). Across all enzymes, the smallest aggregates had the greatest activity and the range of enzyme activities observed in all aggregates 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 ß-glucosidaseon the same aggregates suggest the presence of both extracellular ß-glucosidase functioning in aggregates with no detectable ATP and also of relatively active microbial communities (high ATP) that have low ß-glucosidase potentials. Studying function at a scale more consistent with microbial habitat presents greater opportunity to link microbial community structure to microbial community function.