AFM Imaging of Bacterial Surface

Bacterial samples were prepared for atomic force microscopy (AFM) according to the method described earlier (70 (link)). Briefly, log-phase P. entomophila and B. thuringiensis (OD₆₀₀ = 0.02) in LB were cultivated for 1 h at 30 °C or 37 °C, respectively, with Kazal peptide Pr13a or with water (control) in the total volume of 300 µl. Then, 300 µl of 20 mM phosphate buffer, pH 6.8, was added. Next, the pellets were gently washed twice with 20 mM phosphate buffer, pH 6.8, and twice with non-pyrogenic water. After final centrifugation, the microorganisms were suspended in 10 µl of non-pyrogenic water, applied onto the surface of freshly cleaved mica discs, and allowed to dry overnight at 28 °C before imaging. The surface of P. entomophila and B. thuringiensis was imaged using NanoScope V AFM (Veeco, USA) in the Analytical Laboratory, Faculty of Chemistry, Maria Curie-Skłodowska University, Lublin, Poland. The measurements were carried out as described in Kordaczuk et al. (70 (link)).