Tellurite uptake by cells of the facultative phototroph Rhodobacter capsulatus is a ΔpH-dependent process

The uptake by light-grown cells of Rhodobacter capsulatus of the highly toxic metalloid oxyanion tellurite (TeO32-) was examined. We show that tellurite is rapidly taken up by illuminated cells in a process which is inhibited by the protonophore carbonyl cyanide-p-trifluoromethoxyphenyl-hydrazone (FCCP) and by the K+/H+ exchanger nigericin. Notably, the light-driven membrane potential (Deltapsi) is enhanced by K2TeO3 greater than or equal to 200 muM. Further, tellurite uptake is largely insensitive to valinomycin, strongly repressed by the sulfhydryl reagent N-ethylethylmaleimide (NEM) and competitively inhibited by phosphate. We conclude that tellurite is transported into cells by a DeltapH-dependent, non-electrogenic process which is likely to involve the phosphate transporter (PiT family). (C) 2003 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.