Tunable biomimetic bacterial membranes from binary and ternary lipid mixtures and their application in antimicrobial testing.

The reconstruction of accurate yet simplified mimetic models of cell membranes is a very challenging goal of synthetic biology. To date, most of the research focuses on the development of eukaryotic cell membranes, while reconstitution of their prokaryotic counterparts has not been fully addressed, and the proposed models do not reflect well the complexity of bacterial cell envelopes. Here, we describe the reconstitution of biomimetic bacterial membranes with an increasing level of complexity, developed from binary and ternary lipid mixtures. Giant unilamellar vesicles composed of phosphatidylcholine (PC) and phosphatidylethanolamine (PE); PC and phosphatidylglycerol (PG); PE and PG; PE, PG and cardiolipin (CA) at varying molar ratios were successfully prepared by the electroformation method. Each of the proposed mimetic models focuses on reproducing specific membrane features such as membrane charge, curvature, leaflets asymmetry, or the presence of phase separation. GUVs were characterized in terms of size distribution, surface charge, and lateral organization. Finally, the developed models were tested against the lipopeptide antibiotic daptomycin. The obtained results showed a clear dependency of daptomycin binding efficiency on the amount of negatively charged lipid species present in the membrane. We anticipate that the models proposed here can be applied not only in antimicrobial testing but also serve as platforms for studying fundamental biological processes in bacteria as well as their interaction with physiologically relevant biomolecules. [Display omitted] • Electroformation method applied for reconstruction of gram-negative and gram-positive bacterial cell membranes. • The use of lipid mixtures instead of commercial lipid extracts allows tuning of the membrane composition. • Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) should not be used interchangeably to model bacterial membranes. • Restricting the model membrane composition to only one or two lipids changes the overall properties of bacterial membranes. • Daptomycin binding efficiency increases with the amount of negatively charged lipids present in the membrane. [ABSTRACT FROM AUTHOR]