Numerical models of iron uptake by phytoplankton cells

Two common strategies for acquisition of iron by terrestrial plants, fungi and bacteria are the excretion of siderophores and the reduction of organic iron-complexes at the cell surface. We investigate the feasibility of thes e strategies for single phytoplankton cells in a marine environment, where diffusion plays a much larger role. Using numerical models we determine the efficiency of both mechanisms, wher e efficiency is defined as the ratio between the increase in iron uptake ra tes and the excretion rate of either siderophores or electrons required to obtain this increase. This allows an estimation of the physiological cost o f either mechanism. Based on our results we discuss how the maximum possibl e efficiency depends on the chemical kinetics of iron coordination reaction s, on the biological kinetics of iron uptake, and on other parameters.