Modulation of flagellar rotation in surface-attached bacteria: A pathway for rapid surface-sensing after flagellar attachment
Fig 10
The MotAB stator is required for tethered bacteria to stop rotating.
Bacteria were incubated with anti-flagellin antibody coated slides for 5 min in the presence or absence of 20 mM cAMP. (A) Behavior of tethered bacteria over time. Videomicroscopy was used to identify bacteria rotating at t = 0, and the behavior of these cells was followed for 45 min. The proportion of rotating cells (red), attached cells (black), and detached cells (white) was determined in 4–8 independent experiments. To compare the percentage of tethered cells that were rotating in presence or absence of cAMP, survival curves were analyzed with a Mantel-Cox test. Exogenous cAMP had a significant effect on PAK ΔmotAB (***, p = 0.0005), but not on PAK ΔflhF ΔmotAB (ns, p = 0.0916). (B) Reversal frequency of tethered bacteria. Movies of tethered bacteria imaged at 100 fps for 60s were analyzed by a custom Matlab script to determine reversal frequency. Each symbol indicates reversals made by an individual cell over 60s (n = 21–23); lines indicate medians. cAMP increases the reversal frequency of ΔflhF, but decreases reversal frequency of the ΔflhF motAB mutant (Kruskal-Wallis with Dunn’s multiple comparison test; *, p <0.05; **, p < 0.01). (C) Rotation speeds of tethered bacteria. CW and CCW rotation speeds were extracted from tethered bacteria analyzed in panel (B).