title: Bacteria May Cope Differently from Similar Membrane Damage Caused by the Australian Tree Frog Antimicrobial Peptide Maculatin 1.1.
abstract: Maculatin 1.1 (Mac1) is an antimicrobial peptide from the skin of Australian tree frogs and is known to possess selectivity toward Gram-positive bacteria. Although Mac1 has membrane disrupting activity, it is not known how Mac1 selectively targets Gram-positive over Gram-negative bacteria. The interaction of Mac1 with Escherichia coli, Staphylococcus aureus, and human red blood cells (hRBC) and with their mimetic model membranes is here reported. The peptide showed a 16-fold greater growth inhibition activity against S. aureus (4 μM) than against E. coli (64 μM) and an intermediate cytotoxicity against hRBC (30 μM). Surprisingly, Sytox Green uptake monitored by flow cytometry showed that Mac1 compromised both bacterial membranes with similar efficiency at ∼20-fold lower concentration than the reported minimum inhibition concentration against S. aureus. Mac1 also reduced the negative potential of S. aureus and E. coli membrane with similar efficacy. Furthermore, liposomes mimicking the cell membrane of S. aureus (POPG/TOCL) and E. coli (POPE/POPG) were lysed at similar concentrations, whereas hRBC-like vesicles (POPC/SM/Chol) remained mostly intact in the presence of Mac1. Remarkably, when POPG/TOCL and POPE/POPG liposomes were co-incubated, Mac1 did not induce leakage from POPE/POPG liposomes, suggesting a preference toward POPG/TOCL membranes that was supported by surface plasma resonance assays. Interestingly, circular dichroism spectroscopy showed a similar helical conformation in the presence of the anionic liposomes but not the hRBC mimics. Overall, the study showed that Mac1 disrupts bacterial membranes in a similar fashion before cell death events and would preferentially target S. aureus over E. coli or hRBC membranes.
authors.affiliation: From the School of Chemistry, Bio21 Institute, The University of Melbourne, Parkville, Victoria 3010, Australia and msani@unimelb.edu.au.
authors.forename: Marc-Antoine
authors.initials: MA
authors.lastname: Sani
authors.affiliation: the Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland 4072, Australia.
authors.forename: Sónia Troeira
authors.initials: ST
authors.lastname: Henriques
authors.affiliation: From the School of Chemistry, Bio21 Institute, The University of Melbourne, Parkville, Victoria 3010, Australia and.
authors.forename: Daniel
authors.initials: D
authors.lastname: Weber
authors.affiliation: From the School of Chemistry, Bio21 Institute, The University of Melbourne, Parkville, Victoria 3010, Australia and.
authors.forename: Frances
authors.initials: F
authors.lastname: Separovic
mesh_terms: D029845:Amphibian Proteins / Q000302:isolation & purification / Q000494:pharmacology*; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000302:isolation & purification / Q000494:pharmacology*; D001001:Anura / Q000378:metabolism; D002308:Cardiolipins / Q000737:chemistry; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects*; D002784:Cholesterol / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000737:chemistry / Q000166:cytology / Q000187:drug effects*; D004926:Escherichia coli / Q000737:chemistry / Q000166:cytology / Q000187:drug effects*; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D008081:Liposomes / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010715:Phosphatidylglycerols / Q000737:chemistry; D013045:Species Specificity; D013109:Sphingomyelins / Q000737:chemistry; D013211:Staphylococcus aureus / Q000737:chemistry / Q000166:cytology / Q000187:drug effects*
chemical_list: C519576:1,1',2,2'-tetraoleoylcardiolipin; D029845:Amphibian Proteins; D023181:Antimicrobial Cationic Peptides; D002308:Cardiolipins; D008081:Liposomes; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010715:Phosphatidylglycerols; D013109:Sphingomyelins; C113499:maculatin-1.1 protein, Litoria; C057561:1-palmitoyl-2-oleoylphosphatidylethanolamine; C060037:1-palmitoyl-2-oleoylglycero-3-phosphoglycerol; D002784:Cholesterol; C028694:1-palmitoyl-2-oleoylphosphatidylcholine
keywords: antibiotic resistance; antimicrobial peptide (AMP); bacteria; competitive lipid environment; membrane biophysics; spectroscopy