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A putative [Na.sup.+]/[H.sup.+] antiporter, Vc-NhaP2, which protects cells of Vibrio cholerae growing at pH 6.0 from high concentrations of external [K.sup.+] is demonstrated. The peculiar cation specificity of Vc-NhaP2 and the presence of its two additional paralogues in the same genome could find potential for the transporter as an effective model for detailed analysis of the structural determinants of the substrate specificity in alkali cation exchangers.

The article presents a study which examines the virulence of metalloproteases generated by various Vibrio species on Pacific oyster Crassostrea gigas larvae. Among the bacterial strains and plasmids examined were Vibrio tubiashii, Vibrio alginolyticus and Vibrio mimicus. Researchers found that culture supernatants of several Vibrio species were highly toxic to Pacific oyster larvae. Their analyses revealed that a non-pathogenic bacterial isolate lacked the ability to generate high levels of extracellular protease. They also found that culture supernatants of these Vibrio species were all toxic to oyster larvae.

Na(+)/H(+) antiporters are ubiquitous membrane proteins that play a central role in the ion homeostasis of cells. In this study, we examined the possible role of Na(+)/H(+) antiport in Yersinia pestis virulence and found that Y. pestis strains lacking the major Na(+)/H(+) antiporters, NhaA and NhaB, are completely attenuated in an in vivo model of plague. The Y. pestis derivative strain lacking the nhaA and nhaB genes showed markedly decreased survival in blood and blood serum ex vivo. Complementation of either nhaA or nhaB in trans restored the survival of the Y. pestis nhaA nhaB double deletion mutant in blood. The nhaA nhaB double deletion mutant also showed inhibited growth in an artificial serum medium, Opti-MEM, and a rich LB-based medium with Na(+) levels and pH values similar to those for blood. Taken together, these data strongly suggest that intact Na(+)/H(+) antiport is indispensable for the survival of Y. pestis in the bloodstreams of infected animals and thus might be regarded as a promising noncanonical drug target for infections caused by Y. pestis and possibly for those caused by other blood-borne bacterial pathogens.