Figure 3

Characterizations of the E144D mutant in Vibrio alginolyticus. The fliG/pomA/pomB mutant (NMB301) harboring pNT1 with a fliG mutation and pYA303 with a wild-type (WT)-pomA and pomB and the fliG mutant (NMB198) harboring pNT1 with a fliG-WT or fliG-E144D mutation were grown and observed by high-intensity dark-field microscopy. (A) The ratio of counterclockwise (CCW) rotation and clockwise (CW) rotation of the fliG mutations is shown in the column. All the experiments were repeated at least 6 times, and average values with standard deviation (SD) are shown. (B and C) The switching frequency in 10 sec was measured. All the experiments were repeated at least 6 times, and average values with SD are shown. Data of (A) and (B) for the WT and E144D mutant are from Fig. 2A,B, respectively. The E144D/G215A mutant did not flagellate, so that it showed 0 on (A,B). (C) The effect of serine in the WT-FliG and E144D mutant. To ignore the effect of chemotactic adaptation, the switching events were observed within 3 min after addition of serine. Serine was added to a final concentration of 0.05, 0.1, 0.5, 1.0, 2.0 and 5.0 mM. 0* in the WT with 2.0 mM serine indicates that few cells switched their rotational direction. The WT and E144D mutant without serine are from the WT and E144D mutant of Fig. 2B, respectively. All the experiments were repeated at least 6 times, and average values with SD are shown. The black bars indicate that P < 0.01 for WT-FliG versus the mutants (A,B) or the V buffer background versus the addition of serine with the V buffer (C) by the Welch’s t-test.