All about Bacteria – Structure and Types

Bacteria are the most abundant living organisms on earth. It is considered as one of the oldest forms of life, as they were the very first organisms to evolve on the planet earth, i.e. it was over 2 billion years before eukaryotes appeared.

Bacteria are a large group of microscopic, unicellular organisms, which have been grouped into prokaryotic, as they lack a true nucleus and comprises a simple cellular structure, including capsule, cell wall,  flagellum, pili, cytoplasm, ribosomes and chromosomes. They microorganisms exist in every place around us and are present in communities of millions. In length, the complete bacteria measure only a few micrometres.

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These prokaryotic microorganisms lack a membrane-bound nucleus. The nucleoid contains the chromosome with its associated proteins and RNA. Their genetic material includes a single, circular bacterial chromosome of DNA found within the cytoplasm. Every bacterial cell has its own plasmids, which are involved in food digestion, replication, etc. These plasmids are small, circular, double-stranded DNA Structure, which are naturally found in all Bacterial cells

The bacterium is the singular word for bacteria. The study of bacteria is known as bacteriology and it is a branch of microbiology. Bacteria were first observed by the Dutch microscopist Antonie van Leeuwenhoek in 1675.

Bacteria reproduce by both sexual and asexual methods. Sexual reproduction in bacteria occurs in the form of genetic recombination and the asexual reproduction occurs by the formation of endospores through binary fission.

Types of Bacteria

There are several different types of bacteria and the classification of Bacteria are mainly based on their

• Mode of Respiration – Aerobic or Anaerobic.
• Nutritional Patterns: Autotrophic or heterotrophic.
• Reproduction: Binary fission, transformation, transduction and conjugation.
• Shapes: coccus, Bacillus, Vibrio, spirillum or spirochete.
• Cell wall composition: Gram-positive and Gram-negative.

Facts about Bacteria

1. Bacteria act as biocontrol agents.
2. Bacteria also acts as a cleaning and disinfectant agents.
3. Some bacteria are useful for humans while some can be harmful.
4. Bacteria play a primary role in regulating biogeochemical systems.
5. These bacteria also protect our body from defending the invading pathogens.
6. Bacteria are present both outside the body and deep inside in our gut which helps indigestion.
7. Bacteria occur in different shapes and sizes – sphere, rod, spiral and spherical shaped.
8. There are many bacteria present in our gut which helps in digestion and protects our body from defending the invading pathogens.
9. Bacteria form a crucial part of the ecosystem, which takes part in activities like production of gases like oxygen, carbon dioxide and nitrogen and minerals like nitrogen, sulphur, etc.
10. There are various applications of bacteria, which includes food and beverage industries, the pharmaceutical industry, in the production of biofuel, biopesticides and so on.

This was a brief introduction to the importance of bacteria. To learn more about the bacteria, their types, and other related topics, visit us at MyNCERT to learn more about NCERT solutions for your exam preparation.