Question

Bacteria with tuft of flagella at one pole are
A. Amphitrichous
B. Peritrichous
C. Atrichous
D. Lophotrichous

Answer 1

Bacterial flagella are filamentous, proteinaceous structures that extend around 20 nm from the surface of bacterial cells. These are long, thread-like, unbranched structures made up of flagellin protein. The main function of flagella is locomotion. Secondary functions include sensation, adhesion, signal transduction and also act as virulence factor.

Complete answer:
Option A- Amphitrichous
Bacteria which contain a single flagellum on both the (opposite) sides of the cell wall are called amphitrichous. These are known as polar flagellum and can rotate clockwise which pushes the bacterial cell forward while anti-clockwise which pulls back the bacterial cell. For example- Aquaspirillum.

Option B- Peritrichous
Multiple flagella are attached all over the surface of the bacterial cell. These rotate anti-clockwise so that the organism can move forward in a single direction.
For example- E.coli, Salmonella.

Option C- Atrichous
Bacterial cell which does not contain any flagella is called atrichous. For example- Shigella.

Option D- Lophotrichous
Bundle of flagella attached at one side of a bacterial cell. These are known as polar flagella and can rotate clockwise and anti-clockwise, making movement in the organism. For example- Pseudomonas fluorescens.

Thus, the correct option is D- Lophotrichous.

Note: Flagella is not a straight structure, it’s helical. It is composed of three parts- basal body, hook and filament. These are sensitive to chemicals and temperatures. Flagella can be prokaryotic or eukaryotic and vary from each other in structure, composition and mechanism.