FIGURE 1.

Cathelicidins inhibit B. anthracis growth. A, RDAs were conducted by incubating 2 × 10⁶ ungerminated Sterne strain spores or mid-log phase bacilli with serially diluted peptides (100-0.1 µM). After an overnight incubation to allow for visible colony growth, zones of growth clearance were measured, and the MEC was calculated using linear regression analysis. Graph values represent the mean calculated MEC from at least eight plates ± SEM. Unpaired, two-tailed Student t tests were used to determine statistical significance. *, p < 0.05; **, p < 0.01; ***, p < 0.001. B, MBDAs were performed in which 1 × 10⁶ bacilli/ml were ali-quoted into wells containing serially diluted peptides. Percent growth was calculated by measuring the OD₆₀₀ of peptide-treated samples normalized to the peptide diluent control samples, which were set to 100% for each experimental repetition. Values represent the mean percentages pooled from three experiments conducted in quintuplicate 6 SEM. Statistical significance was determined by two-tailed, one-sample t tests in which each sample was compared against the peptide diluent control. *, p < 0.05; **, p < 0.01; ***, p < 0.001.