Correlation between the respiration-driven Na+ pump and Na+-dependent amino acid transport in moderately halophilic bacteria

Abstract

The effect of Na+ on amino acid uptake by moderately halophilic bacteria was examined using α-aminoisobutyric acid (AIB) as a nonmetabolizable amino acid analogue. Of the eight moderate halophiles investigated, the six Gram-negative bacteria that have a respiration-driven Na+ pump specifically required Na+ for AIB uptake. On the other hand, the two Gram-positive bacteria that have no respiration-driven Na+ pump showed no requirement for Na+ for AIB uptake. Thus, the mode of energy coupling to amino acid transport was quite different between the Gram-negative and Gram-positive moderate halophiles tested: the former, but not the latter, utilized Na+ circulation for the active uptake of AIB.