Characterization and Surface Organization of E. Coli Adhesins
An important initial step in bacterial infections is the adhesion of the pathogenic bacteria to host cells or tissue. This phenomenon has been studied with intestinally pathogenic as well as with extraintestinal and invasive bacteria. Adhesion is mediated by bacterial recognition proteins, which are termed as adhesins. Since adhesive bacteria also induce agglutination of host red blood cells (RBC), the recognition proteins are also called hemagglutinins (1). They are associated with extracellular structures which may have different appearances in the electron microscope. Some of these extracellular appendages are relatively thick and rigid and others are much thinner, flexible and curly. Both can be demonstrated directly by negative staining procedures. A third group of extracellular adhesive structures can only be visualized after stabilization with specific antibodies and has then a capsule-like appearance. These structures, which are schematized in Fig. 1, are termed as fimbriae (rigid, 5–7 nm diameter), fimbrillae (flexible, 2–3 nm diameter) and nonfimbrial (no fine structure demonstrable). Pending their morphological analysis, the term “nonfimbrial” for the latter structures is only tentative.
KeywordsImmunoelectron Microscopy Polysaccharide Capsule Extracellular Structure Important Initial Step Immunogold Technique
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