THE ROLE OF PROTONIC AND SODIUM POTENTIALS IN THE MOTILITY OF ESCHERICHIA-COLI AND BACILLUS FTU

The motility of Escherichia coli and of alkalo- and halotolerant Bacil lus FTU has been studied. It is found that Bac. FTU motility (i) requi res Na+, (ii) is resistant to the protonophorous uncoupler pentachloro phenol (PCP) if cells grow at high pH, and is sensitive to the uncoupl ers at neutral pH, (iii) is sensitized to the uncouplers with the addi tion 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 no t require Na+, (b) is always uncoupler-sensitive, (c) is amiloride-res istant, and (d) can be supported by an artificially-imposed gradient o f 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, respective ly. In Bac. FTU growing at alkaline pH, the Na+ motors arc assumed to be energized by DELTAmu(Na+)BAR produced by the Na+-motive respiratory chain, and therefore DELTAmu(H+)BAR is not involved in the motility p rocess. As to Bac. FTU growing in a neutral medium, DELTAmu(Na+)BAR is produced secondarily, via the Na+/H+-antiporter, i.c., at the expense of DELTAmu(H+)BAR formed by the H+-motive respiratory chain.