Fig. 3: Interspecies variation in flagellar wrapping and its advantages in confined spaces.

a Phylogenetic tree of Burkholderia sensu lato group based on 16S ribosomal RNA sequences. Stinkbug-associated Caballeronia, plant-associated Paraburkholderia, pathogenic Burkholderia sensu stricto group, and Pandoraea species are highlighted with blue, green, red, and yellow, respectively⁷. b Swimming speed for 1.0 s in growth medium for each species. c Cell displacement for 1 min in Q-1D. Box plots in (b–c) represent the minimum, maximum, sample median, and the first and third quartiles (N = 20 cells). d Infection ratio of the bean bug R. pedestris (data derived from our previous paper⁷). e Fluorescently labeled flagellar filament of C. insecticola, B. anthina, and P. norimbergensis in Q-1D. The edge of the narrow passage is presented by dashed yellow lines. The arrows indicate the moving direction of each cell. See Movie S10. f The fraction of flagellar filament morphology in growth medium and Q-1D. The wrapped, unwrapped, incompletely wrapped, and uncategorized flagella are colored by red, purple, and, blue, respectively. Gray indicates uncategorized flagella that could not be clearly assigned to any of the defined categories. g Numerical calculations of time-averaged flow field around the bacterial model in a narrow tube. Left: Unwrapped mode. Right: Wrapped mode. White arrows are the streamline and contour color indicate the velocity component in the swimming direction normalized by the swimming speed U. h Swimming speed U as a function of the gap in the cylinder tube ΔR. The values are normalized by the swimming velocity of the unwrapped mode in the free space U₀ and a half body length H/2, respectively. The gap width between was defined geometrically and systematically varied in the numerical simulations to assess its effect on propulsion. i Snapshot of cell behavior in Q-1D. Fluorescently labeled flagellar filament of C. insecticola WT and ΔcheA. See Movie S13. Source data are provided with this paper.