CORRELATION BETWEEN THE RESPIRATION-DRIVEN NA-DEPENDENT AMINO-ACID-TRANSPORT IN MODERATELY HALOPHILIC BACTERIA( PUMP AND NA+)

The effect of Na+ on amino acid uptake by moderately halophilic bacter ia was examined using alpha-aminoisobutyric acid (AIB) as a nonmetabol izable amino acid analogue. Of the eight moderate halophiles investiga ted, 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 s howed 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 .