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A pilus (Latin for 'hair'; pl.: pili) is a hair-like cell-surface appendage found on many bacteria and archaea. [1] The terms pilus and fimbria (Latin for 'fringe'; plural: fimbriae ) can be used interchangeably, although some researchers reserve the term pilus for the appendage required for bacterial conjugation .
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] The short fimbrial tip is made of the subunits PapK, PapE, PapF and the tip adhesin PapG, which mediates the binding.
The Saf pilin N-terminal extension protein domain helps the pili to form, via a complex mechanism named the chaperone/usher pathway. It is found in all c-u pilins. [8] This protein domain is very important for such bacteria, as without pili formation, they could not infect the host. Saf is a Salmonella operon containing a c-u pilus system. [8]
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 ).
Three types of gliding motility in bacteria are: a) Type IV pili: A cell attaches its pili to a surface or object in the direction it is traveling. The proteins in the pili are then broken down to shrink the pili pulling the cell closer to the surface or object that was it was attached to. [7]
Listeria monocytogenes is a bacteria that can contaminate food and cause serious complications for some. BrucePac and Boar's Head had recent recalls due to listeria risk.
Twitching motility is a form of crawling bacterial motility used to move over surfaces. Twitching is mediated by the activity of hair-like filaments called type IV pili which extend from the cell's exterior, bind to surrounding solid substrates, and retract, pulling the cell forwards in a manner similar to the action of a grappling hook.
The Pilus subunits polymerise via a non-covalent interaction to form the mature pilus which consists of an adhesive tip, helical body and an usher bound base. The P-pilus (pap) system is one of the best characterised and is shown below. [2] A schematic overview of the pap chaperone-usher system showing all subunits and their organisation.