FIG. 5.

Concentration- and time-dependent inhibition of the growth of bacteria and yeasts by synthetic and recombinant gallinacin-6. The data are means ± standard deviations (n = 3). (A) In colony-counting assays, E. coli, S. enterica serovar Typhimurium, C. jejuni, C. perfringens, S. aureus, C. albicans, and S. cerevisiae (∼2.5 × 10⁶ CFU/ml) were incubated for 3 h with various concentrations of synthetic Gal-6. S. cerevisiae cells were counted after 24 h of incubation on agar media at 25°C. All other strains were counted after 24 h of incubation on agar media at 37°C. (B) Additional colony-counting assays were performed with E. coli (•), S. enterica serovar Typhimurium (○), S. aureus (▿), and C. perfringens (▾) in 1% TSB containing 10 mM phosphate buffer (pH 6.5) as described above. (C) Inhibition of E. coli, S. enterica serovar Typhimurium, S. aureus, and C. perfringens in 1% TSB containing 10 mM phosphate buffer, pH 6.5 (white bars), supplemented with 20 mM (gray bars) or 150 mM (black bars) NaCl. (D) The killing kinetics of 16 μg/ml sGal-6 (▾), 64 μg/ml sGal-6 (▿), and 16 μg/ml rGal-6 (○) were determined against logarithmic phase C. perfringens cells in minimal medium (∼2.5 × 10⁶ CFU/ml for sGal-6, ∼2.5 × 10⁵ CFU/ml for rGal-6) in kill-curve studies. During a 150-min incubation time at 37°C under anaerobic conditions, aliquots were removed at various times and incubated overnight at 37°C on TSA plates, and surviving colonies were counted. Bacteria resuspended in minimal medium in the absence of antimicrobial peptide and subjected to the same experimental conditions served as controls (•). All kill-curve studies were performed in duplicate.