What is Fimbriae?
- Fimbriae and pili are filamentous structures composed of protein that extend from the surface of a cell and can have many functions.
- Fimbriae are short, thin, hair-like performances that are thinner than flagella and should not participate in the movement.
- A cell that can be covered with up to 1000 fimbriae.
- They are only visible under an electron microscope due to their small size.
- These are thin tubes consisting of helically arranged protein subunits, with a diameter of 3 to 10 nm and a length of up to several micrometers.
What is Pili?
- Pili are similar to fimbriae but are typically longer.
- Only one or a few pili are present on the surface of a cell.
- Because pili can be receptors on certain types of viruses, they can be seen under a microscope where they are coated with particles.
- Many classes of pili are known, distinguished by their structure and function.
Similarities Between Fimbriae and Pili
- Both the fimbriae as well as pili are filamentous in structure.
- Both fimbriae and pili are attached with the bacterial cell surfaces.
- Both are made up of proteins but these proteins may be different.
Difference Between Fimbriae and Pili
|Structure||Fimbriae are tiny, bristle-like structure||Pili are hair like, and tubular in structure|
|Presence||Present in both gram positive and gram negative bacteria||Present only in gram negative bacteria|
|Protein Composition||Composed of Fimbrillin protein.||Composed of Pilin protein.|
|Length||Fimbriae are shorter as compared to pili||Pili are longer as compared to fimbriae|
|Diameter||They are thinner than pili||They are thicker than fimbriae|
|Number/Cell||200-400 fimbriae/cell||1-10 pili/cell|
|Rigidity||Fimbriae are less rigid than pili||Pili are more rigid than fimbriae|
|Administered by||Fimbriae are administrated by bacterial genes in the nucleoid area.||Pili are administrated by plasmid genes.|
|Role in Attachment||Play important role in attaching the cells||Do not take part in cell attachment|
|Role in Conjugation||They do not take part in cell conjugation||They play important role in cell conjugation|
|Role in Motility||Do not function as a motility||Some pili take part in motility. i.e. Type IV pili|
|Main Function||Main function of fimbriae is attachment of cell surface||Main function of pili is conjugation of cells|
|Examples||Salmonella typhimurium, Shigella dysenteriae.||Neisseria gonorrhoeae|
References and Sources
- Bacterial Flagella, Fimbriae and Pili, Capsule
- Fimbriae vs Flagella
- Instruments used in Microbiology Laboratory
- Algae – Definition, Classification, and Examples
- Bacterial Growth and Nutrition
- Serial Dilution in Microbiology
- Negative Staining
- Types of Extremophiles
- Nutritional Requirements of Micro-Organisms