Question

Describe the structure of bacteria in detail and also its classification according to the shape of their cells.

Answer 1

A bacterium has an outer covering known as the cell wall. Nuclear material is represented by a nucleoid without nuclear membrane.

1. An extra chromosomal DNA called plasmid is present in the cytoplasm.
2. Protein synthesis is carried out by 70S ribosomes. Other cell organelles (mitochondria, golgi body, endoplasmic reticulum etc.,) are absent.
3. Flagella aids in locomotion.

Bacteria are classified according to the shape of their cells. They are:
• Bacilli: Rod shaped bacteria.
Eg. Bacillus anthracis
• Spirilla: Spiral shaped bacteria.
Eg. Helicobacter pylori
• Cocci: Spherical or ball shaped bacteria. They can stick together in pairs (diplococcus) or form a chain (streptococcus) or occur in bunches (staphylococcus).
• Vibrio - Comma shaped bacteria. Eg. Vibrio cholera.