Lecture notes in Microbiology

Difference between Pili and Flagella of Bacteria- A Comparison Table


Fimbria vs pilus

Flagella vs Pili of Bacteria: A Comparison Table
(Similarities and Differences between Pili and Flagella of Bacteria)

Both Flagellum (plural Flagella) 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 motility, attachment, adhesion and assisting in genetic exchange.

Flagella definition: Bacterial flagella are long whip-like filamentous structures present in some bacteria. The most important function of flagella is to assist in locomotion. Flagella can also act as a sensory organ to detect temperature and the presence of certain chemicals in the external environment of the cell. Even though the flagella are present in prokaryotes and eukaryotes, both are entirely different in their structure, formation and mechanism of propulsion.

Pili definition: Pili are long hair like tubular micro-fibres like structures present on the surface of some Gram-negative bacteria. They are comparatively shorter filamentous structures than flagella 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 present post describes the Similarities and Differences between Flagella and Pili with a Comparison Table

Similarities between Flagella and Pili

Ø  Both flagella and pili are filamentous structures.

Ø  Both are cell surface appendages.

Ø  Both are made up of proteins.

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Lecture notes in Microbiology

Difference between Pili and Fimbriae of Bacteria- A Comparison Table


Difference between Pili and Fimbriae

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.

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