Fimbriae vs Flagella
(Similarities and Differences between Fimbriae and Flagella of Bacteria)
Both Fimbria (plural Fimbriae) and Flagellum (plural flagella) are the filamentous proteinaceous structures found on the surface of some bacterial cells.
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).
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 and formation and mechanism of propulsion.
The present post describes the Similarities and Differences between Fimbriae and Flagella of bacteria with a Comparison Table.
Similarities between Fimbriae and Flagella
Ø Both fimbriae and flagella are filamentous structures.
Ø Both are present in Gram positive and Gram negative bacteria.
Ø Both are cell surface appendages, present on the cell surface of bacteria.
Ø Both are made up of proteins.
Ø Formation of flagella and fimbriae are controlled by nucleoid genes.
Difference between Fimbriae and Pili
Sl. No. Fimbriae Flagella
1 Fimbriae are bristle-like short fibres occurs on the surface of bacteria. Flagella are long whip-like filamentous structures occur on the surface of some bacteria.
2 Examples of bacteria having fimbriae
Salmonella typhimurium, Shigella dysenteriae.
Examples of bacteria having Flagella:
Escherichia coli, Helicobacter pylori, Salmonella typhimurium.
3 Fimbriae are external in origin, originated from the cell wall. Flagella are interior in origin, originated from the cytoplasmic membrane.
4 Fimbriae are a solid structure. Pili are hollow tubular structures.
5 Fimbriae are straight and non-helical in nature. Flagella are helical and non-straight in nature.
6 Fimbriae are comparatively shorter in length than flagella. Flagella are many times longer than fimbriae.
7 Approximate length of fimbriae is 0.03 to 0.14 µm. Approximate length of flagella highly varies. (it is about 15 to 20 µm).
8 Fimbriae are made up of fimbrillin protein. Flagella are made up of flagellin protein.
9 The total number of fimbriae per cell may range 200 – 400. Usually, the number of flagella are very limited, one to few.
10 Fimbriae are evenly distributed on the entire surface of the cell. Flagella usually show a distinct pattern of distribution. Distribution may be polar, lateral or throughout the surface.
11 The fimbriae are comparatively thinner in their diameter. Flagella are comparatively thicker than fimbriae.
12 Fimbriae are less rigid structures than flagella. Flagella are more rigid structures than fimbriae.
13 The main function of fimbriae is surface attachment. Fimbriae do not have any role in bacterial motility. The main function of flagella is locomotion. Flagella do not have any role in surface attachment.
14 Fimbriae are not associated with a motor system for propulsion. Bacterial flagella are always associated with a complex motor system at the base for propulsion.