What are bacteria?

Bacteria are microscopic single-celled organisms that are found almost everywhere on Earth. They are among the simplest and oldest forms of life.

Bacteria can live in soil, water, air, food, inside plants, animals, and even extreme environments.

Characteristics of Bacteria

• Single-celled organisms

• Microscopic in size

• Reproduce rapidly by binary fission

• Can survive in different environmental conditions

• Some are useful while others are harmful

Shapes of Bacteria

Bacteria commonly occur in different shapes:

Shape	Description
Cocci	Spherical bacteria
Bacilli	Rod-shaped bacteria
Spirilla	Spiral-shaped bacteria
Vibrios	Comma-shaped bacteria

Useful Bacteria

Beneficial bacteria help in:

• Making curd and cheese

• Nitrogen fixation in soil

• Digestion in the human intestine

• Production of antibiotics and vitamins

• Decomposition of dead matter

Examples:

• Lactobacillus in curd formation

• Rhizobium in nitrogen fixation

Harmful Bacteria

Some bacteria cause diseases in humans, animals, and plants.

Examples:

• Cholera

• Tuberculosis

• Typhoid

• Food poisoning

Reproduction in Bacteria

Most bacteria reproduce through binary fission, where one bacterial cell divides into two identical cells.

Importance of Bacteria

Bacteria are important because they:

• Maintain ecological balance

• Recycle nutrients

• Support agriculture and food industries

• Help in biotechnology and medicine

Although some bacteria are harmful, many are essential for life and environmental health.