Microorganisms, or microbes, are tiny living organisms that are too small to be seen with the naked eye. They exist everywhere—in soil, water, air, and even inside our bodies. While some microbes are beneficial, others can cause diseases. Understanding their role helps us use them wisely and protect ourselves from harm.
Where Are Microorganisms Found?
- Soil & Water – Bacteria, algae, and fungi thrive here.
- On Plants & Animals – Some microbes live symbiotically, while others cause infections.
- Food – Bread, milk, and fruits can grow mould if left in moist conditions.
Why Do They Matter?
- Helpful Microbes – Used in food production, medicine, and environmental cleanup.
- Harmful Microbes – Cause diseases in humans, animals, and plants.
Types of Microorganisms
1. Bacteria
- Single-celled organisms.
- Examples: Lactobacillus (used in curd), Rhizobium (fixes nitrogen in soil).
- Diseases: Typhoid, tuberculosis.
2. Fungi
- Include yeasts and moulds.
- Examples: Penicillium (makes antibiotics), Saccharomyces (used in bread and alcohol).
- Diseases: Skin infections, food spoilage.
3. Protozoa
- Single-celled, often found in water.
- Examples: Plasmodium (causes malaria), Amoeba (can cause dysentery).
4. Viruses
- Not considered living cells—they need a host to multiply.
- Examples: Flu virus, polio virus, HIV.
Where Do Microorganisms Live?
Microbes are extremely adaptable and can survive in:
- Extreme cold (Antarctica) and heat (volcanic springs).
- Inside human and animal bodies (gut bacteria).
- On decaying organic matter (compost, rotting food).
Helpful Microorganisms
1. In Food Production
- Curd & Yogurt – Lactobacillus bacteria ferment milk.
- Bread & Alcohol – Yeast (Saccharomyces) helps dough rise and ferments sugar into alcohol.
- Cheese & Pickles – Bacteria and fungi enhance flavor and preservation.
2. In Medicine
- Antibiotics – Penicillin (from mould) kills harmful bacteria.
- Vaccines – Weakened/dead microbes train the immune system (e.g., polio vaccine).
3. In Agriculture
- Nitrogen-fixing bacteria (Rhizobium) enrich soil fertility.
- Decomposers – Break down dead plants into organic manure.
4. Environmental Cleanup
- Microbes decompose organic waste, reducing pollution.
- They cannot break down plastics or metals.
Harmful Microorganisms
1. Disease-Causing Microbes (Pathogens)
| Type | Diseases | Transmission |
|---|---|---|
| Bacteria | Cholera, Tuberculosis | Contaminated water, air |
| Viruses | Flu, COVID-19, Chickenpox | Air, direct contact |
| Protozoa | Malaria (via mosquitoes) | Mosquito bites |
| Fungi | Ringworm, Athlete’s foot | Skin contact |
2. Food Spoilage
- Microbes produce toxins, making food unsafe.
- Prevention: Proper storage, pasteurization, and preservatives (salt, sugar, vinegar).
3. Plant & Animal Diseases
- Citrus canker (bacteria), wheat rust (fungi).
- Anthrax (bacteria) in cattle.
Food Preservation Methods
| Method | How It Works | Examples |
|---|---|---|
| Refrigeration | Slows microbial growth | Milk, vegetables |
| Pasteurization | Heating milk to kill bacteria | Packaged milk |
| Salting | Removes moisture, inhibits bacteria | Fish, pickles |
| Sugaring | High sugar concentration prevents decay | Jams, jellies |
| Canning | Seals food in airtight containers | Canned fruits, vegetables |
Harnessing Microbes: Practical Applications
Food Preservation Techniques
Traditional Methods
- Drying (removes moisture microbes need)
- Salting (creates hypertonic environment)
- Smoking (combines drying and antimicrobial chemicals)
- Fermentation (promotes good microbes that crowd out bad ones)
Modern Methods
- Refrigeration (slows microbial growth)
- Canning (heat sterilization + airtight sealing)
- Pasteurization (kills pathogens in liquids)
- Irradiation (uses radiation to sterilize)
Industrial Applications
Biotechnology
- Producing enzymes for detergents
- Manufacturing vitamins and amino acids
- Creating bioplastics from microbial byproducts
Energy Production
- Biogas from anaerobic digestion
- Bioethanol from microbial fermentation
- Microbial fuel cells generating electricity
Mining
- Bioleaching extracts metals from ores
- Used for copper, gold, and uranium
- More environmentally friendly than chemical methods
Nitrogen Cycle & Soil Fertility
- Nitrogen Fixation – Bacteria (Rhizobium) convert atmospheric nitrogen into usable forms for plants.
- Absorption by Plants – Plants take in nitrogen compounds for growth.
- Consumption by Animals – Animals get nitrogen by eating plants.
- Decomposition – Dead matter is broken down by microbes, returning nitrogen to the soil.
- Denitrification – Some bacteria release nitrogen back into the air.
Why is this important?
- Maintains soil fertility naturally.
- Reduces the need for chemical fertilizers.
Questions & Answers
1. Why is a small amount of curd added to milk to make more curd?
- Curd contains Lactobacillus, which ferments milk into curd. Adding a starter culture speeds up the process.
2. Why should we prevent communicable diseases?
- They spread easily (e.g., cold, flu) and can cause outbreaks. Prevention: Hygiene, vaccination, and avoiding sick individuals.
3. Why should we avoid stagnant water?
- Mosquitoes breed in stagnant water, spreading diseases like malaria and dengue.
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