INHIBITORY EFFECT OF SODIUM-CHLORIDE ON METHYLAMMONIUM UPTAKE BY A SALT-TOLERANT YEAST - ZYGOSACCHAROMYCES-ROUXII

Uptake of methylammonium, an analogue of ammonium, by Zygosaccharomyces rouxii cells grown without sodium chloride (NaCl) was found to be reduced by the presence of NaCl in the uptake-reaction mixtures. The reduced uptake was almost inversely proportional to NaCl concentration, up to 15%. As for Saccharomyces cerevisiae, in Z. rouxii cells grown with NaCl, however, high activities of methylammonium uptake and ammonium consumption even in the presence of NaCl was found. Kinetic analysis of methylammonium uptake by Z. rouxii showed that the cells grown with NaCl provided an uptake system with a large V(max) value. It was thought that an enhanced uptake system enabled Z. rouxii to incorporate enough ammonium to support its vigorous growth in the presence of NaCl. Attempts were made to discover the mechanism for the increase in V(max), but no evidence for the induction by NaCl of a new transport system for methylammonium or ammonium was obtained.