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. 2023 May 11;24(7):e55338. doi: 10.15252/embr.202255338

Figure 3. The CP1‐WT peptide causes membrane damage and shows bactericidal action on stationary phase cells of Salmonella Typhimurium, Staphylococcus aureus and a carbapenem‐resistant MDR strain of Acinetobacter baumannii .

Figure 3

  • A–D
    Peptide‐induced membrane damage was studied by confocal microscopy and measured by propidium iodide (PI) influx (% PI uptake) in (A) S. Typhimurium, (B) A. baumannii, (C) S. aureus and (D) P. aeruginosa.
  • E–H
    Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Dose (MBD) estimation of CP1‐WT on stationary phase cells of (E) S. Typhimurium, (F) A. baumannii, (G) S. aureus and (H) P. aeruginosa. No bactericidal action is observed for P. aeruginosa. In each of the panels and its corresponding bar graph, the black lines and black bars represent the MIC data indicated by their OD600 values, and the red lines and red bars represent the MBD data indicated by their CFU/ml values. The bar graphs in each panel depict control reactions used for each strain where the cells were treated with DMSO, peptides and ciprofloxacin (Cip – positive control; 10 μg/ml). The strain of A. baumannii used was reported to be ciprofloxacin‐resistant (Nagarajan et al, 2018) as is observed here (inset in panel F).

Data information: In panels (A–D), n = 5 biological replicates; scale bars: 5 μm. Representative images are shown. In the bar graphs, data are presented as mean ± SD values of percentage of propidium iodide uptake (% PI uptake), averaged across all the replicates. 3, 7, 8 and 3% DMSO, and 80, 50, 50 and 80 μM of the peptides in the respective DMSO concentrations were used to treat S. Typhimurium, A. baumannii, S. aureus and P. aeruginosa respectively. In panels (E–H), n = 5 biological replicates. Data are presented as mean ± SD values, averaged across all the replicates. For the bar graphs in these panels, 7, 13, 8 and 4% DMSO, and 80, 100, 100 and 50 μM of the peptides were used for S. Typhimurium, A. baumannii, S. aureus and P. aeruginosa respectively. N.T. – No treatment; WT – CP1‐WT peptide; Mut – CP1‐Mut peptide (negative control). P‐values are calculated by Student's unpaired t‐test; ns P > 0.05; ***P < 0.001; ****P < 0.0001.