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

Abstract

The uptake by light-grown cells of Rhodobacter capsulatus of the highly toxic metalloid oxyanion tellurite (TeO 3 2−) 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 (Δ ψ) is enhanced by K 2TeO 3≥200 μM. 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 ΔpH-dependent, non-electrogenic process which is likely to involve the phosphate transporter (PiT family).