Effect of KCl and NaCl on Uptake of Proline in Staphylococcus aureus

Effect of KCl and NaCl on Uptake of Proline in Staphylococcus aureus

Staphylococcus aureus, the most salt-tolerant food-borne pathogen, produces enterotoxins which may cause symptoms such as vomiting, diarrhea, nausea, and cramps. Since this bacterium has been able to grow at extremely high osmolarity its identity in foods with low water activity values such as salted or dried foods is of great concern. In this study, the growth of S. aureus at high osmolarity has been studied and the doubling time of S. aureus grown at TSB medium containing 15% NaCl has been found to be increased to 4∼5 hours. The stimulation of proline uptake after exposure of cells to high concentration of both extracellular KCl and sucrose was not increased. Stimulation of proline uptake at these environment only occured when 25mM NaCl was present I transport buffer. In additional experiments, the time required to reach mid-logarithmic phase in defined medium of high osmolarity found to be reduce by the presence of glycine betaine, proline, and choline.