Microorganisms: Friend and Foe

Microorganisms Overview

  • Definition: Microorganisms, or microbes, are living organisms that cannot be seen with the naked eye. Examples include fungi on spoiled bread.
  • Observation Activity:
    • Collect moist soil in water; observe under a microscope to see microorganisms.
    • Observe pond water under a microscope to see tiny, moving organisms.

Classification of Microorganisms

  • Major Groups:
    • Bacteria: Unicellular organisms; some are pathogenic.
    • Fungi: Includes yeasts and molds; some cause food spoilage.
    • Protozoa: Unicellular organisms; some are pathogens (e.g., malaria).
    • Algae: Some species are microscopic.
    • Viruses: Microscopic agents that reproduce only inside host cells (causes diseases like polio and influenza).

Habitats of Microorganisms

  • Microorganisms can adapt to various environments: ice cold, hot springs, deserts, and marshy lands.
  • They are present inside animal bodies and can live independently or in colonies.

Benefits of Microorganisms

  • Friendly Microorganisms:
    • Used in food production (e.g., curd formation from Lactobacillus).
    • Alcoholic fermentation: Yeast converts sugar into alcohol.
    • Environmental cleaning: Microorganisms decompose organic waste into harmless substances, aiding soil fertility.
    • Examples:
    • Curd Formation: Bacteria convert milk to curd.
    • Bread Making: Yeast helps dough rise by producing CO2.
    • Commercial Use: Yeast used for large-scale alcohol and vinegar production.

Medicinal Uses

  • Antibiotics are substances derived from microorganisms (e.g., penicillin from mold). Used to combat bacterial infections.
  • Important Advisory: Antibiotics should be taken as prescribed by a doctor to avoid resistance and health complications.
  • Vaccines: Introduce harmless microbes to bolster immune response against diseases like smallpox and polio.

Harmful Microorganisms

  • Pathogens: Microorganisms that cause diseases in humans, plants, and animals. Common diseases include:
    • Cholera
    • Tuberculosis
    • Measles
  • Pathogens can be transmitted via air, water, food, or direct contact.
  • Insects like houseflies and mosquitoes can carry pathogens.

Food Safety and Preservation

  • Food Spoilage: Caused by microorganisms that produce toxins.
  • Preservation Methods:
    • Chemical Methods: Use of preservatives like salt, sugar, vinegar to inhibit microbial growth.
    • Heat Treatment: Boiling and pasteurization kill harmful microbes.
    • Cold Storage: Refrigeration slows down microbial activity.

Nitrogen Fixation and the Nitrogen Cycle

  • Nitrogen Fixation: Process by which certain bacteria (like Rhizobium) convert atmospheric nitrogen into compounds usable by plants.
  • Nitrogen Cycle: Describes the movement of nitrogen through the environment and its conversion from atmospheric to bioavailable forms by microbes.

Key Terms to Remember

  • Microorganism: A microscopic living organism.
  • Pathogen: A microorganism that causes disease.
  • Antibiotic: A medicine that inhibits the growth of or destroys microorganisms.
  • Vaccine: A substance that stimulates the production of antibodies and provides immunity against diseases.
  • Fermentation: The conversion of sugar into alcohol by yeast under anaerobic conditions.
  • Nitrogen Cycle: The process in which nitrogen is converted into multiple chemical forms as it circulates among atmosphere, terrestrial, and marine ecosystems.