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
| Factors | Fimbriae | 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
- https://www.easybiologyclass.com/difference-between-flagella-and-fimbriae-of-bacteria-a-comparison-table
- https://microbenotes.com/flagella-and-pili-fimbriae/
- https://microbiologynote.com/fimbriae-and-pili/
- https://www.differencebetween.com/difference-between-pili-and-vs-flagella/
Further Readings
- 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
- Extremophiles
- Nutritional Requirements of Micro-Organisms
