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Microorganisms Overview

  • Microorganisms are defined as microscopic organisms that cannot be seen with the naked eye.

  • They can be solitary or exist in colonies.

  • Generally classified into five major types:

    • Bacteria

    • Algae

    • Fungi

    • Protozoa

    • Viruses

Types and Characteristics of Microorganisms

Bacteria

  • Simplest microscopic organisms known.

  • Sizes: Ranges from 0.2 to 100 microns.

  • Shapes include:

    • Cocci (spherical)

    • Bacilli (rod-shaped)

    • Spirilla (spiral-shaped)

    • Vibrios (comma-shaped)

  • Examples include Lactobacillus and Rhizobium.

  • Functions:

    • Nitrogen fixation

    • Food production (curd, cheese)

    • Antibiotics production

  • Diseases caused by bacteria:

    • Human: cholera, typhoid, tuberculosis, diphtheria, whooping cough.

    • Plant diseases: blight of paddy, citrus canker.

Algae

  • Simple plants without roots, stems, or leaves; contain chlorophyll.

  • Size ranges from 1 micron to several meters.

  • Examples: Chlamydomonas, Spirogyra, other seaweeds.

  • Importance:

    • Serve as food for aquatic and terrestrial animals.

    • Contribute to soil fertility through nitrogen fixation.

    • Used in product manufacturing (agar-agar, iodine).

Fungi

  • Largest group of microorganisms with over 1,000 known species.

  • Non-photosynthetic; important for decomposition.

  • Made up of hyphae, except for yeast.

  • Diseases caused by fungi in humans include:

    • Mildew, athlete's foot

    • Plant diseases like potato blight.

Protozoa

  • Unicellular, animal-like organisms without chlorophyll.

  • Examples: Amoeba, Plasmodium, Paramecium.

  • Size ranges from 2 to 200 microns.

  • Some cause diseases in humans (amoebic dysentery, malaria).

Viruses

  • Extremely small; cannot be seen without an electron microscope.

  • Sizes range from 0.015 to 0.2 microns.

  • Require hosts to reproduce and can cause various diseases:

    • Common cold, influenza, AIDS.

Microbial Habitats

  • Microorganisms are ubiquitous: found in air, water, soil, and living organisms.

  • They can survive in extreme conditions:

    • Hot springs

    • Ice-cold waters

    • Saline environments

    • Decomposed organic matter.

Microorganisms: Friend or Foe?

Friendly Microorganisms

  • Beneficial roles:

    • In food production (curd and bread making).

    • Environmental clean-up (decomposition).

    • Nitrogen fixation in soil enhancing fertility.

Harmful Microorganisms

  • Pathogens that can cause diseases in humans, animals, and plants.

  • Examples of communicable diseases:

    • Common cold, cholera, tuberculosis.

    • Spread through contaminated air, water, food, or direct contact.

Prevention of Diseases

  • Methods to prevent the spread of communicable diseases:

    • Maintain food hygiene (cover food).

    • Drink safe water.

    • Vaccination to prevent diseases like smallpox, polio.

Food Preservation Techniques

  • Methods of Preservation:

    • Salting: Reduces water content preventing microbial growth.

    • Refrigeration: Low temperatures inhibit microbial activity.

    • Dehydration: Removal of moisture hampers microbial growth.

    • Canning: Sealing food in airtight containers to keep it fresh.

    • Using Preservatives: Chemicals like sodium benzoate to prevent spoilage.

Nitrogen Cycle

  • Continuous circulation of nitrogen between the atmosphere and living organisms.

  • Nitrogen-fixing bacteria convert atmospheric nitrogen into usable compounds for plants.

  • Important for maintaining soil fertility.