FIG. 3.

Effects of the Na⁺ channel inhibitor EIPA, the uncoupler CCCP, and PVP-mediated viscosity increase on swimming speed. (A) Swimming speeds were assayed for the wild type (○), CPS-M with the wild-type motAB locus and an up-motile ccpA-motPS operon expressed from the amyE locus (•), and the ΔPS strain that is deleted for motPS and wild type for motAB (▵) after pregrowth without (left) or with (right) 200 mM added Na⁺ at pH 6.0, 7.0, 8.0, and 8.5 in the presence or absence of EIPA. The values shown are the percent inhibition by EIPA calculated from data shown in the supplemental material (see Fig. S2 in the supplemental material). (B) The same strains used in A were pregrown overnight in TY medium plus 200 mM NaCl (pH 7.0) at 37°C. A 20-μl sample was used to inoculate 1 ml of fresh medium. After 6 h, each culture was diluted 50-fold with TY medium plus 200 mM NaCl (pH 8.5), with a range of CCCP (left) or PVP (right) concentrations.