Abstract
The growth of Vibrio alginolyticus and V. costicola, which possess respiration-dependent Na+ pumps, was highly resistant to the proton conductor carbonyl cyanide-m-chlorophenyl hydrazone (CCCP), in alkaline growth media, even though the membrane was rendered permeable to H+. The pH dependence of CCCP-resistant growth was similar to that of the Na+ pump. In contrast, Escherichia coli ML308-225 showed neither Na+ pump activity nor CCCP-resistant growth, even when grown in alkaline, Na+-rich media. These results suggest that certain bacteria possess the Na+ pump and are thus able to grow under the conditions where H+ circulation across the membrane does not take place. Moreover, V. alginolyticus growing in the presence of CCCP maintains normal levels of internal K+, Na+, and H+. The Na+ pump, therefore, makes the growth of these organisms resistant to CCCP by maintaining the intracellular cation environments.