The role of protonic and sodium potentials in the motility of E. coli and Bacillus FTU

Abstract

The motility of Escherichia coli and of alkalo- and halotolerant Bacillus FTU has been studied. It is found that Bac. FTU motility (i) requires Na +, (ii) is resistant to the protonophorous uncoupler pentachlorophenol (PCP) if cells grow at high pH, and is sensitive to the uncouplers at neutral pH, (iii) is sensitized to the uncouplers with the addition of monensin, (iv) sensitive to amiloride and (v) can be supported by an artificially imposed Na + gradient in the presence of uncoupler, cyanide and arsenate. On the other hand, E. coli motility (a) does not require Na +, (b) is always uncoupler-sensitive, (c) is amiloride-resistant, and (d) can be supported by an artificially-imposed gradient of H +, not Na +. It is concluded that the motilities of Bac. FTU and E. coli are due to the operation of the Na + and the H + motors, respectively. In Bac. FTU growing at alkaline pH, the Na + motors are assumed to be energized by Δ \\ ̄ gm Na + produced by the Na +-motive respiratory chain, and therefore Δ \\ ̄ gm H + is not involved in the motility process. As to Bac. FTU growing in a neutral medium, Δ \\ ̄ gm Na + is produced secondarily, via the Na + H +- antiporter , i.e., at the expense of Δ \\ ̄ gm H + formed by the H +-motive respiratory chain.