Microorganisms

1. Introduction:

• Microscopic World:
  • Observations reveal the presence of numerous tiny organisms in water and soil.
  • Microorganisms, or microbes, are too small to be seen with the naked eye.

2. Classification of Microorganisms:

• Size and Visibility:
  • Microbes vary in size; some, like fungi on bread, are visible with a magnifying glass.
  • Others require a microscope for observation, hence termed microorganisms.
• Major Groups:
  • Microorganisms are classified into four major groups:
    1. Bacteria
    2. Fungi
    3. Protozoa
    4. Some Algae
• Microscopic Viruses:
  • Viruses are also microscopic but distinct from other microorganisms.
  • They reproduce inside host cells, including bacteria, plants, or animals.

3. Diseases Caused by Microorganisms:

• Viral Infections:
  • Common ailments like colds, influenza, and coughs result from viral infections.
  • Viruses also cause serious diseases like polio and chickenpox.
• Protozoan Diseases:
  • Dysentery and malaria are caused by protozoa (protozoans).
• Bacterial Diseases:
  • Bacterial diseases include typhoid and tuberculosis (TB).

Where do Microorganisms Live?

Microorganisms exhibit diverse habitats, adapting to various environments based on their characteristics.

1. Cellular Structure:

• Single-Celled and Multicellular:
  • Microorganisms vary in cellular structure.
  • Some, like bacteria, algae, and protozoa, are single-celled.
  • Others, such as certain algae and fungi, are multicellular.

2. Environmental Range:

• Wide Range of Environments:
  • Microorganisms thrive in diverse environments, covering:
    • Ice-cold climates
    • Hot springs
    • Deserts
    • Marshy lands

3. Living Inside Hosts:

• Within Animal Bodies:
  • Microorganisms inhabit the bodies of animals, including humans.
  • They play roles in various bodily functions.

4. Growth Patterns:

• On Other Organisms:
  • Some microorganisms grow on the surfaces of other living organisms.
  • This includes fungi that may grow on plants or animals.
• Free Existence:
  • Others exist freely in the environment, without being dependent on a host organism.

Microorganisms and Us

Microorganisms play diverse roles in our lives, contributing both benefits and challenges. Let’s explore their impact in detail.

1. Friendly Microorganisms:

• Role in Food Production:
  • Microorganisms are integral to food preparation.
  • Bacteria like Lactobacillus aid in curd formation, cheese, and pickles.
  • Yeast contributes to the fermentation of idlis, dosa batter, and the leavening of bread.
• Commercial Applications:
  • Large-scale production of alcohol, wine, and acetic acid involves microorganisms like yeast.
  • Fermentation, the conversion of sugars into alcohol, is a key process.

2. Medicinal Use of Microorganisms:

• Antibiotics:
  • Antibiotics, derived from bacteria and fungi, combat disease-causing microorganisms.
  • Streptomycin, tetracycline, and erythromycin are examples.
  • Antibiotics are crucial for treating various diseases in humans, animals, and plants.
• Vaccines:
  • Vaccines, made from weakened or dead microbes, stimulate the immune system.
  • Antibodies produced provide immunity against diseases like cholera, tuberculosis, smallpox, and hepatitis.

3. Protection and Eradication:

• Vaccination Campaigns:
  • Childhood vaccinations protect against diseases, emphasizing the importance of immunization.
  • Vaccination campaigns, like the Pulse Polio Programme, target specific diseases, ensuring global health.
• Eradication Efforts:
  • Worldwide campaigns, such as the fight against smallpox, have led to its eradication in many regions.
  • Microorganism-based vaccines contribute to disease prevention on a large scale.

4. Soil Fertility and Environmental Cleanup:

• Biological Nitrogen Fixation:
  • Certain bacteria fix nitrogen from the atmosphere, enhancing soil fertility.
  • Biological nitrogen fixers play a crucial role in agricultural practices.
• Environmental Cleaning:
  • Microbes aid in decomposing organic waste, converting it into manure.
  • The decomposition process contributes to nutrient cycling and helps clean the environment.

Harmful Microorganisms

Microorganisms exhibit harmful activities that impact human health, plants, animals, and various materials. Understanding these harmful aspects is essential to prevent and mitigate their adverse effects.

1. Disease-Causing Microorganisms:

• Transmission to Humans:
  • Pathogens, disease-causing microorganisms, enter the human body through air, water, food, or direct contact.
  • Communicable diseases spread from infected individuals to healthy ones through various mediums.
• Common Communicable Diseases:
  • Examples include cholera, common cold, chickenpox, and tuberculosis.
  • Airborne diseases, like common cold, can spread through fine droplets released when an infected person sneezes.
• Carriers of Diseases:
  • Insects and animals, such as houseflies and mosquitoes, act as carriers of pathogens.
  • Flies can transfer microbes from garbage to uncovered food, leading to infections.
  • Mosquitoes, like the female Anopheles and Aedes, transmit diseases like malaria and dengue.
• Control Measures:
  • Preventing water accumulation in surroundings helps control mosquito breeding.
  • Keeping food covered and maintaining cleanliness minimizes the risk of foodborne illnesses.

2. Disease-Causing Microorganisms in Animals:

• Examples:
  • Anthrax, caused by bacteria, poses a threat to both humans and cattle.
  • Foot and mouth disease in cattle is attributed to a virus.

3. Disease-Causing Microorganisms in Plants:

• Crop Diseases:
  • Various microorganisms cause diseases in plants, impacting crops like wheat, rice, potato, and fruits.
  • Crop yield reduction is a consequence of these diseases.
• Control Measures:
  • Certain chemicals are employed to control the spread of plant diseases by eliminating the microbes.

4. Food Poisoning:

• Microbial Growth on Food:
  • Food poisoning can result from consuming food contaminated by microorganisms that produce toxic substances.
  • Spoiled food can lead to severe illness or even death.
• Preservation Importance:
  • Proper food preservation is crucial to prevent microbial growth and food poisoning.
  • Preservation methods help maintain food safety and quality.

Food Preservation

Food preservation is essential to prevent the spoilage of food caused by microorganisms. Various methods are employed to extend the shelf life of different food items.

1. Chemical Methods:

• Use of Preservatives:
  • Salts and edible oils are common chemicals used as preservatives to inhibit the growth of microorganisms.
  • Preservatives like sodium benzoate and sodium metabisulphite are added to pickles, jams, and squashes to prevent spoilage.

2. Preservation by Common Salt:

• Traditional Method:
  • Common salt has been used for ages to preserve meat and fish.
  • Meat and fish are covered with dry salt to prevent bacterial growth, ensuring longer preservation.
  • Amla, raw mangoes, and tamarind are also preserved using salting.

3. Preservation by Sugar:

• Use in Jams and Jellies:
  • Jams, jellies, and squashes are preserved by sugar.
  • Sugar reduces moisture content, inhibiting bacterial growth that causes food spoilage.

4. Preservation by Oil and Vinegar:

• Effective Preservation:
  • Pickles are preserved by immersing them in a mixture of oil and vinegar.
  • The hostile environment created by oil and vinegar prevents the growth of spoilage-causing bacteria.

5. Heat and Cold Treatments:

• Boiling and Refrigeration:
  • Boiling is employed to kill many microorganisms in food items like milk.
  • Refrigeration inhibits microbial growth by maintaining a low temperature.
  • Pasteurization, discovered by Louis Pasteur, involves heating milk to about 70°C for a short duration, followed by rapid cooling to prevent microbial growth.

6. Storage and Packing:

• Sealed Packaging:
  • Dry fruits and vegetables are often sold in sealed, airtight packets to prevent microbial contamination.
  • Proper storage and packaging play a crucial role in preserving the quality and safety of food products.

Nitrogen Fixation

Nitrogen fixation is a crucial process that converts atmospheric nitrogen into a form usable by plants. The involvement of microorganisms, particularly the bacterium Rhizobium, plays a significant role in this process.

1. Role of Rhizobium:

• Symbiotic Relationship:
  • Rhizobium forms a symbiotic relationship with leguminous plants, including beans and peas.
  • It resides in the root nodules of these plants, as illustrated in Fig. 2.9.
  • Within the nodules, Rhizobium performs nitrogen fixation, converting atmospheric nitrogen into a form that the plant can assimilate.

2. Other Sources of Nitrogen Fixation:

• Lightning:
  • In some instances, nitrogen fixation can occur through the action of lightning.
  • However, the contribution of lightning to overall nitrogen fixation is relatively small.

3. Constant Nitrogen Levels:

• Balanced Nitrogen Cycle:
  • Despite the various processes involved in nitrogen fixation and utilization, the overall amount of nitrogen in the atmosphere remains constant.
  • The nitrogen cycle, encompassing processes like fixation, assimilation, ammonification, nitrification, and denitrification, maintains a balance in nitrogen levels.

Nitrogen Cycle

The nitrogen cycle is a crucial natural process that maintains the balance of nitrogen in the Earth’s atmosphere and ensures its availability for living organisms. Understanding this cycle is vital for appreciating the interconnectedness of various ecological processes.

1. Atmospheric Nitrogen:

• Abundance:
  • Our atmosphere comprises 78% nitrogen gas.
  • Nitrogen is a fundamental component of proteins, chlorophyll, nucleic acids, and vitamins in living organisms.

2. Nitrogen Fixation:

• By Bacteria and Blue Green Algae:
  • Certain bacteria and blue-green algae in the soil play a pivotal role in nitrogen fixation.
  • They convert atmospheric nitrogen into nitrogen compounds, making it accessible to plants.

3. Utilization by Plants and Animals:

• Plant Assimilation:
  • Plants absorb nitrogen compounds from the soil through their root systems.
  • Nitrogen is utilized by plants for synthesizing proteins and other essential compounds.
• Transfer to Animals:
  • Animals, in turn, obtain these proteins and nitrogen compounds by consuming plants.

4. Decomposition:

• Bacterial and Fungal Action:
  • When plants and animals die, bacteria and fungi in the soil facilitate the decomposition process.
  • Nitrogenous wastes are converted into nitrogenous compounds, making them available for reuse by plants.

5. Return to the Atmosphere:

• Nitrogen Gas Release:
  • Some bacteria convert a portion of nitrogenous compounds back into nitrogen gas.
  • This nitrogen gas returns to the atmosphere.
  • This completes the cycle, maintaining the relatively constant percentage of nitrogen in the atmosphere.