A 31P NMR study of the interaction of amphibian antimicrobial peptides with the membranes of live bacteria

Abstract

Amphibian skin is a rich source of peptides that are specificto pathogens and act by disrupting bacterial membranes. Threeantimicrobial peptides were isolated from the skin glands ofAustralian tree frogs, Litoria caerulea and Litoriagenimaculata. NMR spectroscopy was used to observe changesinduced by these peptides in the 31P resonances of bacterialmembranes in vivo. Caerin 1.1 and maculatin 1.1, both wide-spectrum antibiotics, disrupted the membranes ofBacillus cereus and Staphylococcus epidermidis (Gram-positive), leadingto an increase in the isotropic 31P NMR signal. Caerin 4.1, anarrow-spectrum antibiotic, however, did not affect the 31Pspectra of these organisms. The results demonstrate the use of31P NMR to study the effects of membrane-disrupting agents onthe membranes of live bacteria.