TRANSPORT OF GLYCINE-BETAINE BY LISTERIA-MONOCYTOGENES

Uptake of [C-14]glycine-betaine by Listerin monocytogenes was stimulated by NaCl with optimal stimulation at 0.4-0.5 M. The glycine-betaine transport system had a K-m of 22 mu M and a V-max of 11.7 nmol(-1) min(-1) mg(-1) protein when grown in the absence of NaCl. When grown in the presence of 0.8 M NaCl the V-max increased to 27.0 nmol(-1) min(-1) mg(-1) protein in 0.8 M NaCl. At NaCl concentrations above 0.5 M the uptake rate of glycine-betaine was reduced. Measurement of intracellular K+ concentrations and fluorescent dye quenching indicated that higher NaCl concentrations also led to a decrease in the electrochemical potential difference across the cytoplasmic membrane. Uptake of glycine was also observed, but this was not stimulated by NaCl.