Fig. 6.

Depletion of MltG in an unencapsulated derivative of strain D39 leads to slow growth and spherical cell shape. Parent strain IU1945 (D39 Δcps) and merodiploid IU9102 (ΔmltG// ΔbgaA::P_Zn-mltG) were grown overnight in BHI broth containing 0.2 mM ZnCl₂ + 0.02 mM MnSO₄, centrifuged to remove Zn²⁺ and Mn²⁺, and resuspended to OD₆₂₀ ≈ 0.005 in BHI broth containing 0.2 mM ZnCl₂ + 0.02 mM MnSO₄ (IU9102 + Zn²⁺) or no Zn²⁺ + Mn²⁺. (IU1945 and IU9102; no Zn²⁺). (A) Growth curves. Titration of IU9102 growth with different concentrations of Zn⁺² indicated maximal growth in 0.2 mM Zn⁺² + 0.02 mM Mn⁺², which was added to prevent zinc toxicity (see Fig. S10). Doubling times before MltG depletion (≈37 min) and after MltG depletion (≈121 min) are indicated. (B) Representaive phase-contrast images taken at the time points marked by arrows in (A). All micrographs are at the same magnification (scale bar = 1 μm). (C) Box-and-whisker plots (whiskers, 5 and 95 percentile) of cell lengths, widths, aspect ratios (cell length to width) and relative cell volumes of IU1945 and IU9102 grown with or without Zn²⁺ and Mn²⁺. Fifty or more cells from two independent experiments were measured as described in Experimental procedures for each strain. P values were obtained by one-way ANOVA analysis (GraphPad Prism, nonparametric Kruskal-Wallis test). *, **, and *** denote p<0.05, p<0.01, and p<0.001 respectively. Comparisons not marked by brackets are not significantly different.