Bacterial Filamentation Assay for Antimicrobial Peptides

Bacterial cell morphology was examined to assess if the peptides cause filamentation of B. pseudomallei cells, indicative of inhibition of in vivo DNA synthesis (Alfred et al., 2013 (link)). About 5 × 10⁵ CFU/ml bacterial suspension was exposed to each peptide at 8× MIC₉₀. Bacterial cells treated with 1× PBS were used as the negative control. After 1 h incubation at 37°C, an aliquot of the reaction mixture was spotted onto a microscope slide, air dried and stained with crystal violet for 1 min. Excess stain was subsequently rinsed off using distilled water and air-dried. All samples were observed using the Leica DM5000B upright microscope (1000× magnification). Each image was captured using identical settings and the experiment was performed in triplicate.