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Responses of extracellular enzymes to simple and complex nutrient inputs Steven D. Allison*, Peter M. Vitousek

Summary: Responses of extracellular enzymes to simple and complex nutrient inputs
Steven D. Allison*, Peter M. Vitousek
Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA
Received 26 February 2004; received in revised form 16 September 2004; accepted 21 September 2004
Soil microbes produce extracellular enzymes that mineralize organic matter and release carbon and nutrients in forms that can be
assimilated. Economic theories of microbial metabolism predict that enzyme production should increase when simple nutrients are scarce
and complex nutrients are abundant; however, resource limitation could also constrain enzyme production. We tested these hypotheses by
monitoring enzyme activities and nutrient pools in soil incubations with added simple and complex nutrient compounds. Over 28 days of
incubation, we found that an enzyme's activity increased when its target nutrient was present in complex but not simple form, and carbon and
nitrogen were available. b-Glucosidase and acid phosphatase activities also increased in treatments where only carbon and nitrogen were
added. Glycine aminopeptidase and acid phosphatase activities declined in response to ammonium and phosphate additions, respectively. In
some cases, mineralization responses paralleled changes in enzyme activity--for example, b-glucosidase activity increased and respiration
was 5-fold greater in soil incubations with added cellulose, ammonium, and phosphate. However, a doubling of acid phosphatase activity in
response to collagen addition was not associated with any changes in phosphorus mineralization. Our results indicate that microbes produce
enzymes according to `economic rules', but a substantial pool of mineral stabilized or constitutive enzymes mediates this response. Enzyme
allocation patterns reflect microbial nutrient demands and may allow microbes to acquire limiting nutrients from complex substrates
available in the soil.
q 2004 Elsevier Ltd. All rights reserved.
Keywords: Decomposition; Extracellular enzymes; Microbes; Carbon; Nitrogen; Phosphorus


Source: Allison, Steven D. - Departments of Ecology and Evolutionary Biology & Earth System Science, University of California, Irvine


Collections: Environmental Sciences and Ecology