Скачать или смотреть Bacterial Flagella - Structure and types of flagella, explained in 5 minutes

Flagella are microscopic hair-like structures involved in the locomotion of a cell. The word “flagellum” means “whip”. The flagella have a whip-like appearance that helps to propel a cell through the liquid.

Bacterial Flagella Structure

The flagella is a helical structure composed of flagellin protein. The flagella structure is divided into three parts:

Basal body

Hook

Filament

Basal Body

It is attached to the cell membrane and cytoplasmic membrane.

It consists of rings surrounded by a pair of proteins called MotB. The rings include:

L-ring: Outer ring anchored in the lipopolysaccharide layer and found in gram +ve bacteria.

P-ring: Anchored in the peptidoglycan layer.

C-ring: Anchored in the cytoplasm

M-S ring: Anchored in the cytoplasmic membrane

Hook

It is a broader area present at the base of the filament. It connects filament to the motor protein in the base.The hook length is greater in gram positive bacteria.

Filament

Thin hair-like structure arising from the hook.


Types of Flagella

There are four different types of flagella:

Monotrichous

A single flagellum at one end or the other. These are known as polar flagellum and can rotate clockwise and anti-clockwise. The clockwise movement moves the organism forward while the anti-clockwise movement pulls it backwards.

Peritrichous

Several flagella attached all over the organism. These are not polar flagella because they are found all over the organism. These flagella rota anti-clockwise and form a bundle that moves the organism in one direction. If some of the flagella break and start rotating clockwise, the organism does not move in any direction and begins tumbling.

Lophotrichous

Several flagella at one end of the organism or the other. These are known as polar flagellum and can rotate clockwise and anti-clockwise. The clockwise movement moves the organism forward while the anti-clockwise movement pulls it backwards.

Amphitrichous

Single flagellum on both the ends of the organism. These are known as polar flagellum and can rotate clockwise and anti-clockwise. The clockwise movement moves the organism forward while the anti-clockwise movement pulls it backwards.