Fig. 2

Phenotypic assays. A The overall virulence (OD₅₄₀, y-axis) of 132 ST239 and 72 ST59 strains evaluated by lysis of erythrocytes by culture filtrates. Values for isolates of sub-lineage A, B and C are shown in red, orange and green respectively. B Biofilm formation ability (OD₅₇₀; y-axis) of all 132 ST239 and 72 ST59 strains with sub-lineages coloured as in Fig. 1. C Cytolytic activity measured by lysis of erythrocytes by culture filtrates for wild-type (WT; blue) and Δchp (chp knockout mutants; red) ST59 strains. Values provide the mean over three replicates per sample. D Growth curves for WT (blue) and Δchp (red) ST59 strains. p-values are provided following the Wilcoxon signed-rank test (A–C) and following the permutation test (D), see the ‘Methods’ section