期刊
DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS
卷 55, 期 10, 页码 1311-1317出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.dsr.2008.05.004
关键词
Nutrient uptake kinetics; Diffusion limitation; Porter limitation; Cell size; Pasciak-Gavis; Michaelis-Menten
类别
资金
- NSF [OCE 0049009]
- NOAA [DE-FG02-00ER63009]
Pasciak and Gavis were first to propose a model of nutrient uptake that includes both physical transport by diffusion and active biological transport across the cell membrane. While the Pasciak-Gavis model is not complicated mathematically (it can be expressed in closed form as a quadratic equation), its parameters are not so easily interpretable biologically as are the parameters of the Michaelis-Menten uptake model; this lack of transparency is probably the main reason the Pasciak-Gavis model has not been adopted by ecologically oriented modelers. Here I derive a Michaelis-like approximation to the Pasciak-Gavis model, and show how the parameters of the latter map to those of the Michaelis-like model. The derived approximation differs from a pure Michaelis-Menten model in a subtle but potentially critical way: in a pure Michaelis-Menten model, the half-saturation constant for nutrient uptake is independent of the density of transporter (or porter) proteins on the cell surface, while in the Pasciak-Gavis model and its Michaelis-like approximation, the half-saturation constant does depend on the density of porter proteins. The Pasciak-Gavis model predicts a unique relationship between cell size, nutrient concentration in the medium, the half-saturation constant of porter-limited nutrient uptake, and the resulting rate of uptake; the Michaelis-like approximation preserves the most important feature of that relationship, the size at which porter limitation gives way to diffusion limitation. Finally I discuss the implications for community structure that are implied by the Pasciak-Gavis model and its Michaelis-like approximation. (c) 2008 Published by Elsevier Ltd.
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