Fimbriae Gram-negative bacteria

Virtually all bacterial species and genera express lectins or lectin-like activities, frequently of more than one type and with different specificities. However, it is usually not known whether individual cells coexpress multiple types of lectin or each lectin is confined to a distinct cell population. Many Gram negative bacteria (for example, Escherichia coli and Salmonellae spp.) and a few Gram positive ones (e.g. certain actinomyces), produce surface lectins that are often in the form of submicroscopic hairlike appendages known as fimbriae (pili) that protrude from the surface of the cells. The best characterized bacterial surface lectins with respect to their molecular properties, carbohydrate specificity and genetics are the type 1 fimbriae specific for mannose and the type P fimbriae specific for galabiose, [Gal(al-4)Gal], produced by many strains of E. coli. Other examples are S fimbriae of E. coli, specific for NeuAc(a2-3)Gal, and type 2... 

The surfaces of some gram-negative bacteria have structures called fimbriae, also known as pill. Many of these structures have been identified as attachment vehicles. Pili are, for the most part, composed of protein, so they tend to react with specific proteinaceous sites based on host cells—amino acids, sequencing, and peptide configurations. 

Duguid used the variation in morphology and haemagglutinating properties of fimbriae from Gram-negative bacteria to develop a classification system. 

Amongst Gram-positive bacteria a single genus, Corynebacterium, has been shown to possess fimbriae. Cells of Corynebacterium renale, responsible for bovine pyelonephritis and cystitis, produce characteristic bundles (0.4 X 10 pm), composed of a number of individual fimbriae each 3 nm in diameter. These appear superficially very similar to the type 4 fimbriae of Gram-negative bacteria. Several studies have indicated that the Coryne-bacteria fimbriae are also important in adhesion and pathogenesis. 

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