For antimicrobial assays, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 15692, Staphylococcus aureus ATCC 25923, and Staphylococcus epidermidis ATCC 12228 were obtained from the American Type Culture Collection (Manassas, VA, United States). Salmonella typhimurium KCTC 1926 and Listeria monocytogenes KCTC 3710 were obtained from the Korean Collection for Type Cultures (Jeollabuk-do, Korea).
Minimum inhibitory concentrations (MICs) of purified PN peptides were assayed according to the Clinical and Laboratory Standards Institute recommendations (Wiegand et al., 2008 (link)). Briefly, bacterial suspension (5 × 105 CFU/ml), obtained by diluting an exponential growth phase culture, was then added into the 96-well plates containing 2-fold serial dilutions of each fraction, the plates were incubated for 18 h at 37°C. MICs of PN peptides were measured in optical density at 600 nm using Versamax™ ELISA Microplate Reader (Molecular Devices, Sunnyvale, CA, United States). PBS, culture media, and melittin were used as growth and growth inhibition controls. The MIC was defined as the lowest concentration of PN peptide that was able to inhibit microbial growth.
Minimum inhibitory concentrations (MICs) of purified PN peptides were assayed according to the Clinical and Laboratory Standards Institute recommendations (Wiegand et al., 2008 (link)). Briefly, bacterial suspension (5 × 105 CFU/ml), obtained by diluting an exponential growth phase culture, was then added into the 96-well plates containing 2-fold serial dilutions of each fraction, the plates were incubated for 18 h at 37°C. MICs of PN peptides were measured in optical density at 600 nm using Versamax™ ELISA Microplate Reader (Molecular Devices, Sunnyvale, CA, United States). PBS, culture media, and melittin were used as growth and growth inhibition controls. The MIC was defined as the lowest concentration of PN peptide that was able to inhibit microbial growth.