The <i>iacP</i> mutant strain has two different types of flagellar filaments.

<p>(A) The bacteria cell surface was immunogold-labeled and negatively stained for transmission electron microscopy. The bacteria were deposited on the grid and incubated with an anti-FljB primary antibody; this was followed by incubation with protein G–gold and negative staining with uranyl acetate. The images at the bottom panel show higher magnification of electron micrographs. The 10-nm gold particles (arrows) decorate the flagella structures. The images are representative of three independent experiments. Scale bars, 0.5 µm. (B) The flagellar filaments were stained with FITC-conjugated anti-FljB antibody and rhodamine-conjugated anti-FliC antibody. The nucleus and bacteria were stained with Hoechst 33342 dye (original magnification, × 630) (Right panel). For each strain, the number of flagella per cell was quantified from at least 50 cells. Error bars indicate the mean ± SD (standard deviation) of three independent experiments. Asterisks indicate statistically significant difference from the control group, determined by a Student’s <i>t</i> test (<i>P</i> < 0.05). (C) To visualize the flagellar filaments on a single bacterium, the images in B panel show magnified views of at least 100 cells.