Fimbriae vs Pili
(Similarities and Differences between Fimbriae and Pili of Bacteria)
Both Fimbria (plural Fimbriae) and Pilus (plural Pili) are the filamentous proteinaceous structures found on the surface of some bacterial cells. They extend from the surface of the bacterial cell wall and can have many functions such as attachment, adhesion and assisting in genetic exchange.
Fimbriae definition: Fimbriae are bristle like short fibres occurs on the surface of some Gram positive and Gram negative bacteria. Fimbriae enable the bacterial cell to stick to the surface of host cells. They also help in the formation of pellicles or biofilms. (Pellicle: thin sheet of cells on the surface of a liquid).
Pili definition: Pili are long hair like tubular micro-fibres like structures present on the surface of some Gram negative bacteria. They are comparatively longer filamentous structures and their number per cell is very limited. There are many classes of pili based on their structure and function. Most of the pili can act as the receptors of some viruses.
The term Pili and Fimbriae are used inter-changeably by many authors in many microbiology text books. However, modern studies have clearly shown that they are two different entities in the bacteria distinguished by their development, structure and functions.
The present post describes the Similarities and Differences between Fimbriae and Pili with a Comparison Table
Similarities between Fimbriae and Pili
Ø Both fimbriae and pili are filamentous structures.
Ø Both are cell surface appendages, present on the cell surface of bacteria.
Ø Both are the attachment or adhesion organs in bacteria.
Ø Both are made up of proteins.