Fig. 4: Bioactivity characterization and action of functional AMPs on E. coli.

a Quantification of membrane damage in E. coli K88 treated with different AMPs using propidium iodide fluorescence. The fluorescence intensity, indicative of membrane permeabilization, is shown as mean ± standard deviation (n = 3). The negative control (NC) represents untreated E. coli K88, while other bars represent various AMPs. Polymyxin B is included as reference antibiotics. Statistical significance is indicated by asterisks (***), P < 0.001 (one-way ANOVA). b Half-maximal cytotoxic concentration (CC50) and half-maximal hemolytic concentration (HC50) values of AMP candidates, along with minimum inhibitory concentrations (MIC) against E. coli K88 and S. aureus (ATCC 29213). All experiments were conducted in triplicate (n = 3 independent experiments) and the results were averaged. Concentration values are expressed in log10 μg/mL. c Fluorescence microscopy images of E. coli K88 cells untreated (control) or treated with Polymyxin B (positive control) and AMPs. Red fluorescence indicates propidium iodide staining, which binds to DNA upon cell membrane disruption, highlighting compromised bacterial cells, marking compromised bacterial cell membranes. Untreated E. coli K88 serves as the control, displaying minimal fluorescence. Scale bar = 5 μm. All experiments were performed in triplicate, yielding reproducible outcomes. A representative figure is presented to illustrate the findings.