Biophysical Society Thematic Meeting | Ascona, Switzerland

Liposomes, Exosomes, and Virosomes: From Modeling Complex Membrane Processes to Medical Diagnostics and Drug Delivery

Poster Abstracts

42-POS Board 21 Membrane-Active/Fusogenic Activity of the Outer Membrane Vesicles from Lysobacter Enzymogenes C3 Paul R. Meers , Michael Ficurilli, Christopher Riviello, Carol Liu. n/a, , USA. Gram negative bacteria produce small ~50-200 nm outer membrane vesicles (OMV) from their outer envelope. OMV have been implicated in activities such as transmission of virulence factors, horizontal gene transfer and development of biofilms. We have found that Lysobacter enzymogenes C3 produces OMV that may be used to disseminate OMV-membrane-associated antifungal antibiotics produced in a polyketide pathway. We used defined, model liposomal membranes and fluorescent lipid probe assays to investigate the apparent fusogenic activity of these OMV. Lysobacter (and E. coli ) OMV appeared to be essentially spontaneously fusogenic with the bare membranes of liposomes composed of fluid lipid mixtures of several compositions. Support for a fusogenic mechanism of interaction was shown by the ability of the same liposome compositions to transfer encapsulated large fluorescently-labeled dextrans (40 kDa) to an OMV density fraction. Under the same conditions, no apparent fusion of liposomes with whole bacterial cells or other liposomes was observed. Heat treatment of the OMV (70 °C) did not inhibit apparent fusion with liposomes or the antifungal activity, suggesting neither is enzymatically driven. When OMV themselves were fluorescently labeled with carobcyanine lipid probes and then incubated with yeast cells, an apparent transfer of the probes to yeast cell membranes could be seen. We also tested the ability of the OMV to mediate transfer of fluorescent dextrans from liposomes to live Lysobacter cells. The presence of OMV greatly enhanced dextran transfer from liposomes to the whole cell fraction, suggesting the possible involvement of fused liposome-OMV products. These results may implicate OMV as a potential interfering factor but also as a potential liposomal fusion target if the goal is to disseminate therapeutics to various secondary targets such as bacterial biofilms, where OMV typically are found and may participate in intercellular transport.

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