Antimicrobial peptide plectasin recombinantly produced in <i>Escherichia coli</i> disintegrates cell walls of gram-positive bacteria, as proven by transmission electron and atomic force microscopy

The rise of antibiotic-resistant bacteria is a major threat to global health. Antimicrobial peptides (AMPs) offer a promising way to combat this. With the CASPON technology, we produced the AMP plectasin comprising three disulfide bonds using <i>Escherichia coli</i>. The activity of purified plectasin with and without a CASPON fusion tag was determined for four gram-positive and four gram-negative bacteria. As anticipated, only gram-positive bacteria showed a growth inhibition response to un-tagged plectasin. Plectasin treatment on gram-positive bacteria was visualized via electron microscopy. Evaluation of atomic force microscopy indicated that plectasin treatment led to increased roughness but maintained thickness. Based on our study, we assume that the CASPON technology can be employed in the future for the production and characterization of medical-grade AMPs.