Where Electrostatics Matter: Bacterial Surface Neutralization and Membrane Disruption by Antimicrobial Peptides SAAP-148 and OP-145

Biomolecules, vol. 12, pp. 1252

Abstract

The need for alternative treatment of multi-drug-resistant bacteria led to the increased design of antimicrobial peptides (AMPs). AMPs exhibit a broad antimicrobial spectrum without a distinct preference for a specific species. Thus, their mechanism, disruption of fundamental barrier function by permeabilization of the bacterial cytoplasmic membrane is considered to be rather general and less likely related to antimicrobial resistance. Of all physico-chemical properties of AMPs, their positive charge seems to be crucial for their interaction with negatively charged bacterial membranes. Therefore, we elucidate the role of electrostatic interaction on bacterial surface neutralization and on membrane disruption potential of two potent antimicrobial peptides, namely, OP-145 and SAAP-148. Experiments were performed on Escherichia coli, a Gram-negative bacterium, and Enterococcus hirae, a Gram-positive bacterium, as well as on their model membranes. Zeta potential measurements demonstrated that both peptides neutralized the surface charge of E. coli immediately after their exposure, but not of E. hirae. Second, peptides neutralized all model membranes, but failed to efficiently disrupt model membranes mimicking Gram-negative bacteria. This was further confirmed by flow cytometry showing reduced membrane permeability for SAAP-148 and the lack of OP-145 to permeabilize the E. coli membrane. As neutralization of E. coli surface charges was achieved before the cells were killed, we conclude that electrostatic forces are more important for actions on the surface of Gram-negative bacteria than on their cytoplasmic membranes.

Authors 7

1. Djenana Vejzović

   University of Graz

   Affiliation as printed

   Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria

2. Paulina Piller

   University of Graz

   Affiliation as printed

   Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria

3. Robert A. Cordfunke Aachen Department of Immunology, Leiden University Medical Center

   Leiden University Medical Center

   Affiliation as printed

   Department of Immunology, Leiden University Medical Center, 2300 ZA Leiden, The Netherlands

4. Jan Wouter Drijfhout Aachen Department of Immunology, Leiden University Medical Center

   Leiden University Medical Center

   Affiliation as printed

   Department of Immunology, Leiden University Medical Center, 2300 ZA Leiden, The Netherlands

5. Tobias Eisenberg

   University of Graz · BioTechMed-Graz

   Affiliation as printed

   Bio TechMed Graz, 8010 Graz, Austria

   Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria

   Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria

6. Karl Lohner Aachen Department of Immunology, Leiden University Medical Center

   University of Graz · Leiden University Medical Center

   Affiliation as printed

   Department of Immunology, Leiden University Medical Center, 2300 ZA Leiden, The Netherlands

   Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria

   Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria

7. Nermina Malanović corresponding

   University of Graz · BioTechMed-Graz

   Affiliation as printed

   Bio TechMed Graz, 8010 Graz, Austria

   Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria

   Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria