Microorganisms: Friend and Foe

• Introduction to Microorganisms

  • Definition: Tiny living organisms not visible with the naked eye
  • Study: Microbiology
  • Habitat: Everywhere (air, water, soil, inside bodies)
  • Major Groups
    • Bacteria: Single-celled (e.g., Lactobacillus)
    • Fungi: Mold, yeast, mushrooms
    • Protozoa: Amoeba, Paramecium
    • Algae: Spirogyra, Chlamydomonas
    • Viruses: Unique, reproduce only inside host cells

• Friendly Microorganisms

  • Commercial Uses
    • Curd & Bread: Lactobacillus makes curd; Yeast causes fermentation for bread
    • Alcohol & Wine: Yeast converts sugar into alcohol (Fermentation by Louis Pasteur)
  • Medicinal Uses
    • Antibiotics: Produced from bacteria and fungi (e.g., Penicillin, Streptomycin)
    • Vaccines: Trigger antibody production against diseases (e.g., Polio, Smallpox, BCG)
  • Agriculture & Environment
    • Soil Fertility: Rhizobium and blue-green algae fix atmospheric nitrogen
    • Clean Environment: Decomposers break down organic wastes into nutrients

• Harmful Microorganisms (Pathogens)

  • Definition: Disease-causing microorganisms in plants, animals, and humans
  • Human Diseases (Communicable)
    • Air-borne: Tuberculosis, Measles, Chickenpox
    • Water/Food-borne: Cholera, Typhoid
    • Insect-borne (Vectors): Malaria (Female Anopheles mosquito), Dengue (Aedes mosquito)
  • Animal Diseases
    • Anthrax: Dangerous human and cattle disease caused by bacteria
    • Foot and Mouth Disease: Affects cattle, caused by a virus
  • Plant Diseases
    • Citrus Canker: Bacteria (Air transmission)
    • Rust of Wheat: Fungi (Air/Seeds transmission)
    • Yellow Vein Mosaic of Okra: Virus (Insect transmission)

• Food Preservation

  • Need: To prevent spoilage and contamination by microbes
  • Methods of Preservation
    • Chemical Methods: Using salts and edible oils (preservatives)
    • Preservation by Common Salt: Used for meat, fish, raw mangoes
    • Preservation by Sugar: Used in jams, jellies, and squashes
    • Preservation by Oil and Vinegar: Prevents bacterial growth in pickles
    • Heat and Cold Treatments: Boiling milk; Refrigeration
    • Pasteurization: Heating milk to ~70°C for 15-30 seconds, then chilling
    • Storage and Packing: Airtight sealed packets for dry fruits and vegetables

• Nitrogen Cycle

  • Atmospheric Nitrogen: 78% in air, unusable directly by plants
  • Nitrogen Fixation
    • Biological: Rhizobium in root nodules of legumes; Blue-green algae
    • Atmospheric/Lightning: High temperature fixes nitrogen in soil
  • Assimilation: Plants absorb nitrogen compounds from soil to make proteins
  • Ammonification: Decomposers convert waste and dead bodies into nitrogen compounds
  • Denitrification: Certain bacteria convert soil nitrogen compounds back into atmospheric nitrogen gas