They are everywhere — in the air, water, soil, inside our bodies, and on every surface.
Types of Microorganisms
1. Bacteria :
- Single-celled, very tiny.
- Some are helpful (like in yogurt, cheese, digestion).
- Some cause diseases (like TB, strep throat).
2. Viruses :
- Even smaller than bacteria.
- Cannot live on their own — they need a host cell to reproduce.
- Cause diseases like cold, flu, COVID-19, measles.
3. Fungi :
- Yeasts, molds, mushrooms.
- Some used in bread, beer, antibiotics.
- Some cause infections (like athlete’s foot).
4. Protozoa :
- Single-celled, larger than bacteria.
- Often live in water.
- Some cause diseases like malaria, dysentery.
5. Algae :
- Mostly live in water.
- Can make their own food via photosynthesis.
- Important for oxygen and aquatic food chains.
Useful / Helpful Microorganisms :
- In food: yeast in bread, bacteria in curd, cheese.
- In medicine: penicillin (from fungus), vaccines, good gut bacteria.
- In nature: decompose dead plants/animals, enrich soil (nitrogen-fixing bacteria).
- In environment: clean oil spills, treat sewage water.
Harmful Microorganisms :
- Cause diseases in humans, animals, plants.
- Spoil food.
- Cause tooth decay, skin infections.
How to Avoid Harmful Microbes :
- Wash hands regularly.
- Drink clean water, eat clean food.
- Get vaccinated.
- Cook food properly.
- Keep wounds clean.
Fun Facts :
- There are more bacteria in your body than human cells.
- Some microbes survive in extreme places — hot springs, ice, deep ocean.
- Microbes are the oldest living things on Earth.
The role of microorganisms in decomposition :
Microorganisims such as bacteria and fungi act as decomposers by feeding on dead and decaying bodies of plants and animals, converting them into simple substances.these simple substances are restored to the soil.thus,the nutrient that were once taken from the soil by plant and animals are fed back into the soil and become ready to use again.had there been no bacteria there would have been piles of dead bodies all over the earth.
Some bacteria are useful in helping to decompose sewage and other waste in water.in village ,animal excreta and plant waste are decomposed by bacteria in the absence of oxygenate produce an excellentnfuel called methane.