Subbacterial vesicles capable of generating delta psi during NADH oxidation were obtained. The oxidation of NADH was stimulated by Na+ and inhibited by 2-heptyl-4-oxyquinoline-N-oxide (HQNO) in submicromolar concentrations. The generation of delta psi was inhibited by HQNO in low concentrations, cyanide, gramicidine D and carbonyl cyanide-m-chlorophenylhydrazone (CCCP) in combination with monensine. At the same time, in the absence of monensine CCCP influenced the delta psi generation in a much lesser degree. In subbacterial vesicles delta psi generation coupled with NADH oxidation necessitated Na+. Experiments with intact cells of V. alginolyticus revealed that cell motility depends on Na+, is sensitive to CCCP + monensine as well as to arsenate + HQNO, cyanide or anaerobiosis. In the absence of arsenate, the inhibition of respiration partly decreased the rate of bacterial movement. In the presence of HQNO and arsenate, NaCl addition to K+-loaded cells led to the monensine preventing restoration of the cell motility during a few minutes. However, no stimulating effect was observed in the case of artificial delta pH formation as a result of acidification of the medium (from pH 8.6 to pH 6.5). The experimental results suggest that delta mu Na+ generated by the respiratory chain and by the arsenate-sensitive enzymatic system (presumably, glycolysis and Na+-ATPase) can be utilized by the Na+-driven molecular motor responsible for the motility of V. alginolyticus cells.