Whole cell 2H Solid-state NMR of Antimicrobial Peptides Interacting with Cell Envelopes: Role of lipopolysaccharide

Antimicrobial Peptides (AMPs) have been studied for more than two decades because of their promise to help overcome the problem of resistance to conventional antibiotics. However, AMPs have not been as successful as it intended, likely because we lack a detailed understanding of their mechanisms of action. Many AMPs have been shown to permeabilize model lipid membranes. Also, it is likely that interactions between AMPs and non-lipid components of the cell envelope are important to their mechanisms of action. Specifically, the focus of this study is to find out if the lipopolysaccharide (LPS) outer membrane layer of Gram-negative bacteria promotes or inhibits AMP-induced membrane disruption. We disrupt the lipopolysaccharide layer of Gram-negative bacteria (JM109) via chelation of the stabilizing divalent cations. Then, we use deuterium NMR of deuterated intact bacteria to observe the level of membrane disruption by the AMPs (MSI-78) with and without EDTA treatment. In addition to 2H NMR, we do light microscopy and flow cytometry to confirm the EDTA disruption of LPS.