Introduction to Microorganisms
Microorganisms are tiny living organisms that cannot be seen with the naked eye.They are visible only under a microscope.
Examples: Bacteria, Fungi, Protozoa, Algae, Viruses.
2. Types of Microorganisms
- Helpful: Curd formation, nitrogen fixation.
- Harmful: Cause diseases like tuberculosis, typhoid.
- 2.Fungi – Can be unicellular (yeast) or multicellular (moulds).
- Helpful: Bread, alcohol production, antibiotics (penicillin).
- Harmful: Spoil food, cause skin diseases.
- 3.Protozoa – Animal-like, unicellular organisms.
- Cause diseases: Malaria (Plasmodium), Amoebic dysentery.
- 4.Algae – Plant-like, photosynthetic microorganisms.
- Example: Chlamydomonas, Spirogyra.Some (blue-green algae) fix nitrogen.
- 5.Viruses – Borderline between living and non-living.Active only inside host cells.
- Cause diseases: Influenza, polio, measles, COVID-19.
- 3. Useful Microorganisms
- In food industry:
- Yeast → bread, alcohol, wine.
- Lactobacillus → curd from milk.
- In medicine:
- Antibiotics (penicillin from fungi).
- Vaccines (prevent diseases like polio, smallpox).
- In agriculture:
- Nitrogen-
- fixing bacteria (Rhizobium, blue-green algae).
- Increase soil fertility.
- In cleaning environment:
- Decompose organic waste → manure.
- 4. Harmful Microorganisms
- Cause diseases in humans, animals, and plants.
- Human diseases: Cholera, typhoid, malaria, influenza.
- Animal diseases: Foot-and-mouth disease.
- Plant diseases: Rust in wheat, citrus canker.
- Spoil food → food poisoning.
- 5. Food Preservation Methods
- To prevent spoiling by microorganisms:
- Drying (remove water).Salting/Sugaring (draws out water).
- Refrigeration/Freezing (slows microbial growth).
- Chemical preservatives (sodium benzoate, sodium metabisulphite).
- Vacuum packing or air-tight containers.
- 6. Nitrogen Cycle
- Microorganisms play a key role in the nitrogen cycle.
- Nitrogen-fixing bacteria convert atmospheric nitrogen into compounds plants can use.
- Decomposers release nitrogen back to soil and atmosphere.
In summary: Microorganisms are both friends and foes – they help in food production, medicine, agriculture, and waste management but can also cause diseases and spoil food.