A gene has been cloned from the marine bacterium Vibrio alginolyticus that functionally complements a mutant strain of Escherichia coli, TO114, defective in three Na+/H+ antiport genes (nhaA, nhaB, chaA). The nucleotide sequence of the cloned fragment revealed an open reading frame, which encodes a protein with a predicted 528 amino acid sequence and molecular mass of 57212 Da. This gene has 62% identity to nhaB gene at the DNA level from Escherichia coli and the deduced amino acid sequence is 67% identical with E. coli NhaB. This gene is presumably the V. alginolyticus nhaB gene and will be named nhaBv.