Uptake of Lipophilic Organic Cu, Cd, and Pb Complexes in the Coastal Diatom Thalassiosira weissflogii

Abstract

Short-term uptake experiments using the coastal diatom Thalassiosira weissflogii demonstrated that low molecular weight, lipophilic, organic Cu, Cd, and Pb complexes enter the cell by diffusion across the plasma membrane. This passive uptake mechanism acts in parallel to facilitated transport, which involves an equilibrium between free metal ions in solution and surface transport sites. Neither the observed permeability coefficents nor the calculated theoretical permeability coefficents for these lipophilic organic compleres account for the increased cellular Cu concentration observed over 5 h. Furthermore, permeability measwements cannot explain the discrepancy in cellular concentrations between Cu, Cd, and Pb in the lipophilic organic metal treatments