Question

Write a short note on bacteria and its structure.

Answer 1

1. Bacteria are single-celled prokaryotes (cells without nuclei).
2. Bacteria are grouped under the kingdom Monera. The study of Bacteria is called Bacteriology.
3. Bacteria are of two types based on respiration
   a. Aerobic bacteria (requires oxygen).
   b. Anaerobjc bacteria (Does not requires oxygen).
4. A bacterium has an outer covering known as the cell wall. The nuclear material is represented by a nucleoid without a nuclear membrane.
5. An extra chromosomal DNA called plasmid is present in the cytoplasm.
6. Protein synthesis is carried out by 70S ribosomes. Other cell organelles (mitochondria, Golgi body endoplasmic reticulum, etc,) are absent. Flagella aids in locomotion.
7. Bacteria are described according to the shape of their cells. They are:
   a. Bacilli – Rod shape bacteria
   b. Spirilla – Spiral shaped bacteria
   c. Cocci – Spherical or ball-shaped bacteria
   d. Vibrio – Comma shaped bacteria
8. Bacteria are also classified according to number and arrangement of flagella as follows:
   a. Monotrichous – Single flagella at one end. Example: Vibrio cholera
   b. Lophotrichous – Tuft of flagella at one end. Example: Pseudomonas.
   c. Amphitrichous – Tuft of flagella at both ends. Example: Rhodospirillum rubrum.
   d. Peritrichous – Flagella all around. Example: E.coli.
   e. Atrichous – Without any flagella. Example: Corynebacterium diptherae.