Loss of PefI-SrgD restores flagellar biosynthesis and flagellar-based motility in Δ hha Δ ydgT. (A). Flagellar-based motility was determined in wild type, Δhha ΔydgT, ΔpefI-srgD and Δhha ΔydgT ΔpefI-srgD using a 0.25% soft agar motility assay. (B). The radius of the motility region was quantified after 6 h. (C). Bacteria and surface flagella were stained with 2% phosphotungstic acid and imaged using a transmission electron microscope. (D). Surface flagella were quantified for at least 100 bacteria cells for each strain. Motility assays are representative of three independent experiments and quantified as means and standard errors. TEM images are representative of two independent experiments.