Ecoenzymatic stoichiometry of microbial organic nutrient acquisition in soil and sediment

The flow of energy and nutrients through an ecosystem is governed by both metabolic limitations and nutrient availability. A study of the external 'ecoenzymes' released into the environment by microbes to digest organic matter now shows that the activity of these enzymes follows a consistent scaling relationship that is independent of microbial community composition. The four enzymes mediating a large fraction of carbon, nitrogen and phosphorus acquisition by heterotrophic microbial communities were measured in soil and freshwater sediments, and the ratio of C to N to P assimilation activity was close to 1:1:1 in all habitats. Ecoenzyme activity can be seen as linking the two principal unifying theories of ecology — stoichiometric and metabolic theories — since enzyme expression is a product of cellular metabolism specifically regulated by the random nature of environmental nutrient availability.