Bacteria fimbriae

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. 

An important virulence factor of bacteria is their ability to adhere to urinary epithelial cells by fimbriae, resulting in colonization of the urinary tract, bladder infections, and pyelonephritis. Other virulence factors include hemolysin, a cytotoxic protein produced by bacteria that lyses a wide range of cells... 

Group II includes bacteria that produce toxins responsible for the course of disease during gastrointestinal invasion. Disease symptoms are the result of cell destruction caused by extracellular toxins and by elements present in the cell wall, e.g., fimbriae. Such toxins are not... 

In addition to flagella, extremely thin, long, straight filaments known as pili or fimbriae (Fig. 1-2) project from the surfaces of many bacteria.14 The "sex pili" (F pili and I pili) of E. coli have a specific role in sexual conjugation. The similar but more numerous common pili or fimbriae range in thickness from 3 to 25 nm and in length from 0.2 to 2 pm. Pili are involved in adhesion of bacteria to surrounding materials or to other bacteria and facilitate bacterial infections.17-19 A typical E. coli cell has 100-300 pili.5... 

Microbial pathogens utilize different types of lectins for targeting the glycans on the surface of host cells. Many bacteria are covered with pili or fimbriae that contain a very special class of lectins known as adhesins because they play a role in attachment to epithelial cells. These lectins are monomeric and comprise only one binding site. Because the adhesins are repeated on the pilus, a larger number of adhesins on the bacterial surface create multivalent interaction with the host glycans. 

Moreover, Sharon (72) has already demonstrated that bacterial lectins at the tip of fimbriae possess subtle but different affinities for aromatic a-D-mannopyranosides, thus illustrating the effect of what we coined sub-site-assisted aglycone binding (75). For instance, a-D-mannopyranosides 2-4 (Scheme 1) showed 69 to 1015-fold increased inhibitory properties in comparison to methyl mannoside 1 (72). Additionally, discrete differences can be observed between the inhibitory properties of a given mannoside derivative against different strains of bacteria, thus illustrating again that selectivity can be achieved. 

E. coli is responsible for 85% of urinary tract infections (20). Virtually all E. coli express type 1 fimbrae, and most uropathogenic E. coli express P fimbriae, which are responsible for mediating the adherence of the bacteria to uroepithelial cells (18). Fructose is responsible for inhibiting the adherence of type-1-fimbriated E. coli, whereas a polymeric compound inhibits P-fim-briated E. coli (18). Recently, a study (21) identified this polymeric compound as condensed tannins (proanthocyanidins) based on the ability of proanthocyanidins purified from cranberries to inhibit the ability of P-fimbri-ated E. coli to attach to isolated uroepithelial cells at concentrations of 10-50 ug/mL. Blueberries, another member of the Vaccinium genus, may be a more palatable source of proanthicyanidins. 

Bacteria are simple unicellular organisms that constantly grow. They have a membrane and cell wall. Fimbriae are especially important for bacterial adhesion, a critical factor in dental disease development. Lipopolysaccharide is a covalent lipid and polysaccharide structure that contains unusual saccharides and fatty acids. The lipid is at one end and inserts it into the plasma membrane. LPS is invariably recognized as foreign by receptors on mammalian cells that recognize the unique structure and activate inflammation such as gingivitis. 

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 expression of fimbriae is phase variable, i.e. bacteria shift periodically between a fimbriated and non-fimbriated state [38]. As a result, a given bacterial population will always contain cells of both phenotypes. The on- and off-phase variation is controlled at the transcriptional level and involves the inversion of a 314-base pair DNA segment harboring the promoter of the fimA. gene [46]. 

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