Microorganisms: Friend and Foe

1.1 Microorganisms

Introduction to Microorganisms

• Microorganisms, or microbes, are living organisms that are too small to be seen with the naked eye.
• Example: During the rainy season, moist bread can get covered with greyish white patches due to fungi.
• This chapter Microorganisms: Friend and Foe, focuses on the various aspects of microorganisms, including their characteristics, beneficial uses, harmful effects, and roles in processes such as disease, food preservation, and the nitrogen cycle.

Observing Microorganisms

• These activities show that water and soil are full of tiny organisms.

Characteristics of Microorganisms

• Microorganisms are very small and require a microscope to be seen.
• Some, like the fungus on bread, can be seen with a magnifying glass.
• They are classified into four major groups:
  1. Bacteria
  2. Fungi
  3. Protozoa
  4. Some Algae
• Viruses are also microscopic but different from other microbes. They reproduce only inside the cells of a host organism (bacteria, plants, or animals).

Examples of Microorganisms and Diseases

• Viruses: Cause common ailments like cold, flu (influenza), and serious diseases like polio and chickenpox.
• Protozoa: Cause diseases like dysentery and malaria.
• Bacteria: Cause diseases like typhoid and tuberculosis (TB).

1.2 Where Microorganisms Live

• Microorganisms can be single-celled (bacteria, some algae, protozoa) or multicellular (many algae, fungi).
• They live in diverse environments like:
  • Ice cold climates
  • Hot springs
  • Deserts
  • Marshy lands
• They can also be found inside animals’ bodies, including humans.
• Some microorganisms live on other organisms, while others exist freely.

1.3 Microorganisms and Us

Microorganisms are tiny living things that can be both helpful and harmful. Let’s explore how they impact our lives.

Friendly Microorganisms

Microorganisms are used in many ways:

• Food Preparation:
  • Making curd, bread, and cake.
• Alcohol Production:
  • Used for making alcohol for ages.
• Environmental Cleanup:
  • Break down organic wastes like vegetable peels and animal remains.
• Medicine Preparation:
  • Bacteria help make medicines.
• Agriculture:
  • Increase soil fertility by fixing nitrogen.

A. Making of Curd and Bread

• Curd Formation:
  • Bacteria like Lactobacillus turn milk into curd.
  • Curd has many microorganisms that help in making cheese, pickles, etc.
  • Curd is used in rava idlis and bhaturas for fermentation.

B. Commercial Use of Microorganisms

• Large Scale Production:
  • Used to make alcohol, wine, and vinegar.
  • Yeast grows on natural sugars in grains and fruits.

Fun Fact

• Louis Pasteur discovered fermentation in 1857.

C. Medicinal Use of Microorganisms

Microorganisms are super helpful in medicine! Let’s see how they help us stay healthy.

Antibiotics

• Purpose:
  • Kill or stop the growth of disease-causing microorganisms.
• Common Antibiotics:
  • Penicillin, streptomycin, tetracycline, and erythromycin.
• Source:
  • Made from bacteria and fungi.
• Usage:
  • Cure various diseases.
  • Mixed with livestock and poultry feed to prevent infections.
  • Used to control plant diseases.

Important Tips

• Take antibiotics only if prescribed by a doctor.
• Complete the full course of antibiotics.
• Wrong use can make antibiotics less effective and kill beneficial bacteria.
• Antibiotics do not work against colds and flu (diseased caused by viruses).

Fun Fact

• Alexander Fleming discovered penicillin in 1929 by observing how mould killed bacteria.

Vaccine

Vaccines help our body learn to fight diseases without actually getting sick.

How Vaccines Work

• Antibodies:
  • When microbes enter the body, antibodies fight them off.
  • The body remembers how to fight these microbes in the future.
• Vaccination:
  • Injecting dead or weakened microbes to produce antibodies.
  • Antibodies stay in the body, offering long-term protection.

Common Vaccines

• Diseases Prevented:
  • Cholera, tuberculosis, smallpox, hepatitis, polio, etc.
• Campaigns:
  • Pulse Polio Programme for polio prevention.
  • Worldwide campaigns have eradicated smallpox.

Fun Fact

• Edward Jenner discovered the smallpox vaccine in 1798.

D. Increasing Soil Fertility

Some bacteria {cyanobacteria (blue green algae)} can take nitrogen from the air and enrich the soil. These bacteria are called biological nitrogen fixers and help make the soil more fertile.

E. Cleaning the Environment

Microorganisms help break down waste and clean the environment.

Decomposition

• Process:
  • Microbes decompose plant and animal waste into simple substances.
  • These substances can be reused by plants and animals.

Microorganisms are amazing tiny helpers, making medicines, vaccines, fertile soil, and a clean environment!

1.4 Harmful Microorganisms

Microorganisms can be harmful in many ways. They can cause diseases in humans, animals, and plants, and they can spoil food, clothing, and leather.

Disease-causing Microorganisms in Humans

• Pathogens: Microorganisms that cause diseases are called Pathogens.
• Transmission:
  • Through air, water, and food.
  • Direct contact with infected persons.
  • Carried by animals and insects.
• Communicable Diseases: Diseases that spread from an infected person to a healthy person.
  • Examples: Cholera, common cold, chicken pox, tuberculosis.
  • Spread by Air:
    • Sneezing spreads viruses in droplets.
  • Spread by Insects:
    • Houseflies: Carry pathogens from garbage to food.
    • Mosquitoes:
      • Female Anopheles: Malaria.
      • Female Aedes: Dengue.

Preventing Mosquito-borne Diseases

• Avoid Water Stagnation: No water collection in coolers, tires, flower pots, etc.
• Keep Surroundings Clean: Prevent mosquitoes from breeding.

Some Common Human Diseases caused by Microorganisms

Human Disease	Causative Microorganism	Mode of Transmission	Preventive Measures
Tuberculosis	Bacteria	Air	Keep the patient in complete isolation. Keep personal belongings of the patient separate.
Measles	Virus	Air	Vaccination to be given at a suitable age.
Chicken Pox	Virus	Air/Contact	Maintain personal hygiene and good sanitary habits.
Polio	Virus	Air/Water	Vaccination. Consume properly cooked food and boiled drinking water.
Cholera	Bacteria	Water/Food	Vaccination. Drink boiled water.
Typhoid	Bacteria	Water	Drink boiled water.
Hepatitis A	Virus	Water	Drink boiled water.
Malaria	Protozoa	Mosquito	Use mosquito nets and repellents. Spray insecticides and control mosquito breeding.

Disease-causing Microorganisms in Animals

• Examples:
  • Anthrax: Caused by bacteria; affects humans and cattle.
  • Foot and Mouth Disease: Affects cattle; caused by a virus.

Robert Koch discovered the bacterium (Bacillus anthracis) which causes anthrax disease in 1876.

Disease-causing Microorganisms in Plants

• Impact: Reduce crop yield.
• Control: Use chemicals to kill microbes.

Some common plant diseases caused by microorganisms:

Plant Diseases	Causative Microorganism	Mode of Transmission
Citrus canker	Bacteria	Air
Rust of wheat	Fungi	Air, seeds
Yellow vein mosaic of bhindi	Virus	Insect

Food Poisoning

• Cause: Consumption of food spoiled by microorganisms.
• Symptoms: Vomiting, serious illness, and sometimes death.
• Prevention: Proper food preservation to prevent spoilage.

Microorganisms can cause many problems, but knowing how they spread and taking preventive measures can help keep us safe and healthy.

1.5 Food Preservation

Food preservation is essential to keep our food safe from spoiling. Let’s learn how we can prevent food from going bad.

Why Preserve Food?

• Spoiling Signs:
  • Bad smell, bad taste, and color change.
• Cause:
  • Microorganisms spoil food.

Common Methods of Food Preservation

1. Chemical Method:
   • Preservatives: Salts and edible oils prevent microorganism growth.
   • Examples: Sodium benzoate and sodium metabisulphite in jams and squashes.
2. Preservation by Common Salt:
   • Usage: Preserves meat, fish, amla, raw mangoes, and tamarind.
   • Method: Cover with dry salt to inhibit bacteria.
3. Preservation by Sugar:
   • Usage: Preserves jams, jellies, and squashes.
   • Method: Reduces moisture content, preventing bacterial growth.
4. Preservation by Oil and Vinegar:
   • Usage: Preserves pickles, vegetables, fruits, fish, and meat.
   • Method: Bacteria cannot survive in oil and vinegar environments.
5. Heat and Cold Treatments:
   • Boiling: Kills microorganisms in milk and other foods.
   • Refrigeration: Inhibits microorganism growth by keeping food at low temperatures.
   • Pasteurisation: Discovered by Louis Pasteur. Milk is heated to about 70°C for 15-30 seconds and then chilled. Pasteurized milk doesn’t need boiling.
6. Storage and Packing:
   • Air-tight Packing: Sealed packets for dry fruits and vegetables prevent microbial attack.

By using these methods, we can keep our food safe and fresh for longer periods.

1.6 Nitrogen Fixation

Rhizobium and Leguminous Plants

• Rhizobium Bacteria:
  • Lives in root nodules of leguminous plants like beans and peas.
  • Helps fix nitrogen from the atmosphere into the soil.
  • Has a symbiotic relationship with the plants, meaning both benefit.

Nitrogen Fixation by Lightning

• Lightning:
  • Can also fix nitrogen in the atmosphere.

1.7 Nitrogen Cycle

Importance of Nitrogen

• Nitrogen in the Atmosphere:
  • Makes up 78% of the air.
• Role in Living Organisms:
  • Essential for proteins, chlorophyll, nucleic acids (DNA), and vitamins.

Nitrogen Fixation

• Process:
  • Certain bacteria and blue-green algae in the soil convert atmospheric nitrogen into usable nitrogen compounds.
• Plant Absorption:
  • Plants absorb these nitrogen compounds through their roots and use them to make proteins.

Nitrogen Transfer

• Animals:
  • Get nitrogen by eating plants.

Decomposition and Return to Atmosphere

• Decomposition:
  • When plants and animals die, bacteria and fungi decompose their nitrogenous wastes into compounds plants can use.
• Conversion to Nitrogen Gas:
  • Other bacteria convert some of these compounds back into nitrogen gas, returning it to the atmosphere.

This cycle keeps the amount of nitrogen in the atmosphere constant.

Chapter Summary:

• Microorganisms are too small to see with the unaided eye.
• They live in all kinds of environments, from ice-cold climates to hot springs, deserts, and marshy lands.
• Microorganisms are found in air, water, and in the bodies of plants and animals.
• They can be unicellular or multicellular.
• Microorganisms include bacteria, fungi, protozoa, and some algae.
• Viruses are different from other microorganisms and are considered microbes.
• Viruses reproduce only inside a host organism, such as a bacterium, plant, or animal cell.
• Some microorganisms are useful for commercial production of medicines and alcohol.
• Some microorganisms decompose organic waste and dead plants and animals into simple substances, cleaning up the environment.
• Protozoans cause serious diseases like dysentery and malaria.
• Some microorganisms grow on food and cause food poisoning.
• Some microorganisms live in the root nodules of leguminous plants and fix nitrogen from the air into the soil, increasing soil fertility.
• Some bacteria in the soil fix nitrogen from the atmosphere and convert it into nitrogenous compounds.
• Certain bacteria convert nitrogen compounds in the soil into nitrogen gas, which is released into the atmosphere.

Keywords:

1. ALGAE
2. ANTIBIOTICS
3. ANTIBODIES
4. BACTERIA
5. CARRIER
6. COMMUNICABLE DISEASES
7. FERMENTATION
8. FUNGI
9. LACTOBACILLUS
10. MICROORGANISM
11. NITROGEN CYCLE
12. NITROGEN FIXATION
13. PASTEURISATION
14. PATHOGEN
15. PRESERVATION
16. PROTOZOA
17. RHIZOBIUM
18. VACCINE
19. VIRUS
20. YEAST