Table 1.
Summary of daughter cells' patterns seen with different flagellum mutantsa.
Figure 1.
Appearance of daughter bacteria growing on LB-HA gel.
JW1923, a fliG-deleted K-12 strain, was grown on a LB-HA (0.5%)-coated slide and the first two rounds of bacterial division were imaged by time-lapsed microscopy. (A) Formation of 4-cell arrays; (B) Patterning in a string; (C) Representatives of non-typical arrangements. Scale bar: 5 µm.
Figure 2.
Patterning of daughter bacteria in liquid without underneath substratum.
Bacterial divisions in LB medium were followed similar to that described in Figure 1. (A) Parental strain BW25113; (B) flagellum-null strain JW1923. In (A), arrowhead indicates a cell separating and disappearing from the bacterial string in the subsequent image. In (B), the arrow indicates bacteria that appeared as a string of four cells while the arrowhead marks a string of 16 offspring bacteria. Note: the balloon-type bacteria were not exactly on the focal plane of the microscope. No bacteria were observed to have a parallel or 4-cell array arrangement in all fields. Scale bar: 5 µm.
Table 2.
Effect of flagella on the string length of dividing bacteria in LB media.
Figure 3.
Measurement of the interaction of the bacterium with the surrounding LB agar in terms of the interaction force constant (Kbio).
The Kbio values, representing the interacting forces between bacterium and 0.2% LB-agar, were measured by oscillatory optical tweezers. In each group, about 20 measurements were performed and every single spot represents a measured Kbio value; the horizontal line marks the average of the group. Asterisk indicates that a statistically significant difference is observed between the paired strains (p<0.001 by t-test).
Figure 4.
Comparison of flagellar rotation frequency.
The flagellar rotation frequencies measured for strains BW25113 and JW1923 in LB medium were compared. A distinct peak was shown at around 185 Hz in the power spectrum of the quadrant photodiode signal for the case of the wild type strain BW25113 (A) but not in the flagella mutant strain JW1923 (B). Arrow indicates the position of the peak.
Figure 5.
Measurement of bacterial motility.
BW25113 and JW1923 in motility medium were tracked by time-lapsed microscopy for 10 min and the recorded images were analyzed to determine the average motility of each bacterium by MetaMorph software. The motilities of the two bacteria differed significantly at P<0.0001 (by t-test).
Figure 6.
Bacterial motility detected on agar plates.
Appropriately diluted bacteria were grown overnight at 37°C on LB plates containing 0.6% or 0.27% agar. No differences of bacterial colonies are seen in panel (A) (0.6% agar) whereas panel B (0.27% agar) shows that the parental BW25113 gave strong swarming activity that is not seen with the ΔfliG mutant.
Table 3.
Summary of daughter cells' patterns seen with various bacterial strainsa.
Figure 7.
Interaction force constants measured for JW1667 and its related plasmid-transformed strains.
JW1667 is an lpp-disrupted strain derived from BW25113 and has a phenotype with a low rate of daughter cells' patterning in parallel. Kbio measurement and illustrations of the measured values are as in Figure 3. Transformation of JW1667 with plasmid pACYC184-lpp was to complement the lost lpp whereas that with pACYC184 transformation was to give a plasmid control. The arrowhead marks the mean Kbio value of BW25113 shown in Figure 3. Asterisks mark the pairs with statistically significant differences (p<0.0001 by t-test).
Table 4.
Bacterial resistance to detergent lysis.
Table 5.
Appropriate complementation converting the phenotype of JW1667 to that seen with the wild type (BW25113) in daughter cells' patterning.
Table 6.
E. coli strains used in this study.