Fig. 2. PBP2SAL responds to host signals to generate rod shape in intracellular Salmonella.
a Morphology of isogenic wild-type (WT), ΔmrdA and ΔPBP2SAL cells in the input cultures after overnight culture in LB nutrient medium at pH 5.8. Scale bar, 5 µm. b Regain of rod shape by the ΔmrdA mutant at 8 h post infection of NRK-49F rat fibroblasts. Shown are the phase contrast image and the fluorescence obtained after labelling with anti-S. Typhimurium primary anti-O-atigen LPS rabbit antibody and a secondary anti-rabbit IgG antibody conjugated to Alexa488. Cellular dimensions (major, minor axes) of four representative rod-shaped intracellular bacteria (numbered from 1 to 4), are shown. (n = 2 biological). c Morphology of WT, ΔmrdA and ΔPBP2SAL cells along the intracellular infection of NRK-49F rat fibroblasts. Shown is the fluorescence obtained after antibody-mediated labelling of the LPS. The readjustment in cell shape is noted in the ΔmrdA mutant from the early times post infection (2 h) (n = 2 biological). Scale bar, 5 µm. d, e Cellular dimensions (length, width) measured in the populations of input (extracellular bacteria) and intracellular bacteria at the indicated post infection times (2, 4, 8 and 24 hpi). Number of bacteria (n) measured in the distinct populations were for WT: 100 (extracellular), 54, 90, 58, and 83 (2, 4, 8 and 24 hpi); for ΔmrdA: 117 (extracellular), 32, 44, 87, and 71 (2, 4, 8 and 24 hpi); and, for ΔPBP2SAL: 92 (extracellular), 44, 52, 82, and 51 (2, 4, 8 and 24 hpi). Major (length) and minor (width) axes were measured using ObjectJ (https://sils.fnwi.uva.nl/bcb/objectj/) and fluorescent images obtained after labelling with anti-LPS antibodies. The mean value in each sample is indicated by a thick horizontal line (n = 2 biological).