Effect of the Na+ channel inhibitor EIPA on motility. Wild-type, MotAB and MotPB-M strains were grown overnight on TY medium, pH 6.0, at 37 C and the MotPS and MotAS-M strains were grown overnight on TY medium, pH 8.5, at 37 C. Each strain was then inoculated into fresh TY medium at the same pH and grown for 6 hours at 37 C. During this growth period 0.6 mM IPTG was added to the culture medium for MotAS-M and MotPB-M. After 6 hours, each culture was dilute 50-fold into TY medium that was prepared as follows for particular strains: MotAB, TY medium, pH 6.0; MotPB-M, TY medium, pH 6.0, with/without 1.5% (w/v) PVP; MotPS, TY medium, pH 8.5, containing 50 mM NaCl; and MotAS-M, TY medium, pH 8.5, containing 100 mM NaCl. The swimming speed of each strain was measured in the presence of EIPA at concentrations over a range from 0-100 μM. The results represent the averages of three independent experiments in which the swimming speed of twenty independent cells was calculated by each experiment.