Applied and Environmental Microbiology, May 1999, p. 1843-1848, Vol. 65, No. 5
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Department of Food Science, Rutgers University, New Brunswick, New Jersey 08901
Received 2 November 1998/Accepted 15 February 1999
Membrane vesicles released by Escherichia coli O157:H7
into culture medium were purified and analyzed for protein and DNA content. Electron micrographs revealed vesicles that are spherical, range in size from 20 to 100 nm, and have a complete bilayer. Analysis
of vesicle protein by sodium dodecyl sulfate-polyacrylamide gel
electrophoresis demonstrates vesicles that contain many proteins with
molecular sizes similar to outer membrane proteins and a number of
cellular proteins. Immunoblot (Western) analysis of vesicles suggests
the presence of cell antigens. Treatment of vesicles with exogenous
DNase hydrolyzed surface-associated DNA; PCR demonstrated that vesicles
contain DNA encoding the virulence genes eae,
stx1 and stx2, and uidA, which
encodes for
-galactosidase. Immunoblot analysis of intact and lysed,
proteinase K-treated vesicles demonstrate that Shiga toxins 1 and 2 are
contained within vesicles. These results suggest that vesicles contain
toxic material and transfer experiments demonstrate that vesicles can
deliver genetic material to other gram-negative organisms.
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