Respiration-Dependent Proton and Sodium Pumps in a Psychrophilic Bacterium, Vibrio Sp. Strain ABE-1

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Respiration-dependent proton and sodium flows in a psychrophilic bacterium, Vibrio sp. strain ABE-1, were examined. At alkaline pH, this bacterium grew without being affected by a proton conductor, carbonylcyanide m-chlorophenylhydrazone (CCCP). O_2-pulse into anaerobic cell suspensions prepared with Na^+-free buffers induced transient alkalization in the presence of CCCP and acidification at pH 8.5 and 6.5, respectively. However, using cells prepared with Na^+-containing buffer, the transient pH changes of the cell suspension could be simultanously detected at both pHs. Several inhibitory experiments suggested that the acidification and alkalization should be attributed to a respiration-dependent primary H^+ pump and Na^+ pump, respectively, and that the latter was similar to that first reported in a marine bacterium, Vibrio alginolyticus. This Na^+ pump may have supported the CCCP-resistant growth at alkaline pH. The H^+ and Na^+ pumps operated very actively at low temperatures, such as 5℃, and should markedly help sustain bacterial growth at low temperatures.
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