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Liposomes, Exosomes, and Virosomes: From Modeling Complex
Membrane Processes to Medical Diagnostics and Drug Delivery
Poster Abstracts
108
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.