EVIDENCE FOR FEEDBACK (TRANS) REGULATION OF, AND 2 SYSTEMS FOR, GLYCINE BETAINE TRANSPORT BY STAPHYLOCOCCUS-AUREUS

Previous reports are in conflict as to the number of transport systems for glycine betaine in Staphylococcus aureus. Cells grown in complex medium exhibited a single transport system of moderate affinity. Cells grown in defined medium in the absence of glycine betaine showed a hi gh affinity and a low affinity transport system. Cells grown in the pr esence of glycine betaine in the presence of osmotic stress in either complex or defined media accumulated large pools of internal glycine b etaine. Smaller, but still significant, amounts of glycine betaine wer e accumulated by cells grown in its presence in either complex or defi ned media in the absence of osmotic stress. Cells grown in defined med ium in the presence of glycine betaine in the presence or absence of o smotic stress showed lower rates of glycine betaine transport than cel ls grown in its absence. This suggests that glycine betaine transport is subject to feedback or trans inhibition by internal glycine betaine . This can explain the difference in observed kinetics in cells grown in complex or defined media, the high affinity system being predominan tly inhibited in cells grown in complex medium.