Affiliation:
1. Department of Biochemistry, University of Groningen, 9747 AG Groningen, The Netherlands
2. National Institute for Public Health, 3720 BA Bilthoven, The Netherlands
Abstract
The high-molecular-weight material released into the medium by
Escherichia coli
AP1, an enterotoxigenic strain of porcine origin, has been isolated and resolved into two clearly distinct fractions, based on sucrose density gradient and differential centrifugation, chemical analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and freeze-fracture electron microscopy. These two fractions, referred to as “medium vesicles” and “medium lipopolysaccharides”, were compared with the cellular outer and cytoplasmic membranes, the periplasmic fraction, and the cytoplasmic fraction. The medium vesicles closely resembled outer membrane and accounted for 3 to 5% of the total cellular outer membrane. They contained most of the heat-labile enterotoxin (LT) activity released into the medium by
E. coli
AP1. The medium lipopolysaccharide consisted mostly of lipopolysaccharide and a small amount of outer membrane and contained relatively little LT activity. Based on experiments with
E. coli
K-12 strains, in which about 5% of the newly synthesized outer membrane is lost from areas of outer membrane synthesis, it is proposed that enterotoxigenic
E. coli
strains release LT as part of such newly synthesized outer membrane fragments and that released outer membrane fragments may function as physiologically significant LT carriers.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
43 articles.
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