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Fimbria (Latin for 'fringe', pl.: fimbriae) is a term used for a short pilus, an appendage that is used to attach the bacterium to a surface, sometimes also called an "attachment pilus" [10] or adhesive pilus. The term "fimbria" can refer to many different (structural) types of pilus.
Chaperone-usher fimbriae (CU) are linear, unbranching, outer-membrane pili secreted by gram-negative bacteria through the chaperone-usher system rather than through type IV secretion or extracellular nucleation systems. These fimbriae are built up out of modular pilus subunits, which are transported into the periplasm in a Sec dependent
A fimbria (plural fimbriae also known as a pilus, plural pili) is a short, thin, hair-like filament found on the surface of bacteria. Fimbriae are formed of a protein called pilin ( antigenic ) and are responsible for the attachment of bacteria to specific receptors on human cells ( cell adhesion ).
Fimbriae usually function to facilitate the attachment of a bacterium to a surface (e.g. to form a biofilm) or to other cells (e.g. animal cells during pathogenesis). A few organisms (e.g. Myxococcus) use fimbriae for motility to facilitate the assembly of multicellular structures such as fruiting bodies.
P fimbriae are large, linear structures projecting from the surface of the bacterial cell. With lengths of 1-2um, the pili can be larger than the diameter of the bacteria itself. [4] The main body of the fimbriae is composed of approx. 1000 copies of the major fimbrial subunit protein PapA, forming a helical rod. [5]
They have other functions, including attachment to solid surfaces. Additionally, protein appendages can be present on the surface: fimbriae and pili can have different lengths and diameters and their functions include adhesion and twitching motility. [11] [12] [3]
Of all the fimbriae, one fimbria known as the ovarian fimbria is long enough to reach and make contact with the near part of the ovary during ovulation. [ 13 ] [ 14 ] [ 12 ] The fimbriae have a higher density of blood vessels than the other parts of the tube, and the ovarian fimbria is seen to have an even higher density.
The fimbrial usher protein is involved in biogenesis of the pilus in Gram-negative bacteria.The biogenesis of some fimbriae (or pili) requires a two-component assembly and transport system which is composed of a periplasmic chaperone and a pore-forming outer membrane protein which has been termed a molecular 'usher'; this is the chaperone-usher pathway.