Characteristics of ion tranport systems in Vibrio parahaemolyticus and Staphylococcus aureus

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Vabrio parahaemolyticus and Staphylococcus aureus are two major causes of food poisoning in Japan. S.aureus is also a major cause of infection in hospitals. The former requires Na^+ for its growth, and the latter is a Na^+-torelant microorganism. Base on these characteristics, we investigated ion transport systems, especially Na^+ transport systems, in these microorganisms. We biochemically and molecular biologically characterized such transport systems, and investigated relationship between halophilicity or halotorelance of these bacteria and Na^+ transport.We characterized the Na^+/H^+ antiporter in V.parahaemolyticus and cloned gene for the antiporter. We thereafter sequenced the gene and revealed the primary structure of the antiporter. We found sequence similarity between the Na^+/H^+ antiporter and the NhaB Na^+/H^+ antiporter of Escherichia coli. Thus, we designated the antiporter of V.parahaemolyticus as NhaB.We identified several functional amino acid residues of the Na^+/H^+ antiporters. We also found the third Na^+/H^+ antiporter NhaD and characterized it. The gene was cloned and sequenced. We found that it was a new type of Na^+/H^+ antiporter. It became claer that the Na^+/H^+ antiporters are very important for halophilicity and halotorelance. The Na^+/glucose symporter (SglS) was also characterized. We cloned the structural gene and sequenced it. We found sequence similarity between the SglS and human SGLT,Na^+/glucose symporter.We developed a method for the preparation of everted membrane vesicles of S.aureus. We found that Na^+/H^+ antiporter is present in this microorganism. We characterized it, cloned the structural genes and sequenced them. This Na^+/H^+ antiporter was revelaed to be a novel type of antiporter. We found that this antiporter is involved in halotorelance and intracellular pH regulation.