Glycine betaine transport by Staphylococcus aureus: evidence for feed back regulation of the activity of two transport systems, Microbiology 140:3131–3138

The transport of glycine betaine by Stuphyfococcus uureus was investigated. Two transport systems were found that could be differentiated on the basis of their affinity for glycine betaine and their activation by osmotic pressure. The high-affinity system was relatively independent of osmotic pressure and exhibited a K, of approximately 3 VM. This system was not inhibited by proline, for which a separate high-affinity transport system has been recently discovered. The low-affinity system was activated approximately 35-fold by an increase in osmotic pressure and exhibited a K, of approximately 1 3 0 ~ ~ for glycine betaine. This system is partially inhibited by excess proline and may be identical to the low-affinity system recently described for proline. Both glycine betaine transport systems are Na+-dependent