Fig. 2: The ΔdmxA mutant has an aberrant motility behavior with aberrant reversals and a cell polarity defect.

a Population-based motility assay. T4P-dependent motility and gliding were analysed on 0.5 and 1.5% agar, respectively. Numbers indicate the colony expansion in 24 h as mean ± SD (n = 3 biological replicates). In the complementation strain, dmxA was expressed from its native promoter from a plasmid integrated into a single copy at the Mx8 attB site. Black, white, and red asterisks indicate p < 0.05, two-sided Student’s t-test against WT (black, white) or the ΔpilA or ΔgltB controls (red). Scale bars, 1 mm (left), 1 mm (middle), 50 μm (right). b, c Single cell-based motility assays. T4P-dependent motility was measured for cells on a polystyrene surface covered with 1% methylcellulose (b) and gliding on 1.5% agar supplemented with 0.5% CTT (c). Cells were imaged for 15 min with 30 s intervals. Speed (n = 60 from three biological replicates with each 20 cells indicated in different colors) and number of reversals (n = 90 from three biological replicates with each 30 cells). Only cells moving during the entire recording interval were included. For speed, error bars represent mean ± SD calculated from all data points. Reversals are represented as histograms based on all three replicates, error bars indicate the median±median absolute deviation (MAD). NA not applicable because cells are non-motile. *p < 0.05, ns not significant; statistical tests: speed, two-sided Mann–Whitney test, reversals, one-way ANOVA multiple comparison test, and Fisher's LSD test. d Quantification of T4P localization based on transmission electron microscopy. Total number of cells from at least three biological replicates indicated above. e Transmission electron microscopy of a ΔdmxA cell, with T4P at both poles. T4P are indicated by black arrowheads. The image in the middle shows the complete cell and the images on the left and right show the two poles. Scale bars, 0.5 µm (left and right), 2 µm (middle). Source data, including exact p values, are provided as a Source Data file.