New Paper in Ecology Letters: Optimal metabolic regulation along resource stoichiometry gradients


Most heterotrophic organisms feed on substrates that are poor in nutrients compared to their
demand, leading to elemental imbalances that may constrain their growth and function. Flexible
carbon (C)-use efficiency (CUE, C used for growth over C taken up) can represent a strategy to
reduce elemental imbalances. Here, we argue that metabolic regulation has evolved to maximise
the organism growth rate along gradients of nutrient availability and translated this assumption
into an optimality model that links CUE to substrate and organism stoichiometry. The optimal
CUE is predicted to decrease with increasing substrate C-to-nutrient ratio, and increase with
nutrient amendment. These predictions are generally confirmed by empirical evidence from a new
database of c. 2200 CUE estimates, lending support to the hypothesis that CUE is optimised
across levels of organisation (microorganisms and animals), in aquatic and terrestrial systems, and
when considering nitrogen or phosphorus as limiting nutrients.