Uptake of sulphate, taurine, cysteine and methionine by symbiotic and free-living dinoflagellates

Abstract

Sulphate uptake by Amphidinium carterae, Amphidinium klebsii and Gymnodinium microadriaticum grown on artificial seawater medium with sulphate, cysteine, methionine or taurine as sulphur source occurred via an active transport system which conformed to Michaelis-Menten type saturation kinetics. Values for Km ranged from 0.18–2.13 mM and Vmax ranged from 0.2–24.2 nmol · 105 cells−1 · h−1. Km for symbiotic G. microadriaticum was 0.48 mM and Vmax was 0.2 nmol · 105 cells−1 · h−1. Sulphate uptake was slightly inhibited by chromate and selenate, but not by tungstate, molybdate, sulphite or thiosulphate. Cysteine and methionine (0.1 mM), but not taurine, inhibited sulphate uptake by symbiotic G. microadriaticum, but not by the two species of Amphidinium. Uptake was inhibited 45–97% under both light and dark conditions by carbonylcyanide 3-chlorophenylhydrazone (CCCP); under dark conditions sulphate uptake was 40–60% of that observed under light conditions and was little affected by 3-(3,4-dichlorophenyl) 1,1-dimethylurea (DCMU).