The role of micro-organisms in disease

Role of Micro-organisms in Disease

Definition of Micro-organisms

  • Microbes are organisms that cannot be seen with the naked eye.

    • Classified into:

    • Bacteria

    • Viruses

    • Fungi

    • Protozoa

    • Animals (specifically referring to parasitic micro-organisms)

  • Characteristics of Micro-organisms:

    • Exhibit rapid reproduction, establishing large populations for laboratory study.

    • Their small size complicates study, requiring equipment like microscopes.

Importance of Studying Micro-organisms

  • Understanding different micro-organisms helps tackle diseases they cause.

  • Key knowledge areas include:

    • Types of micro-organisms.

    • Differences between infectious and non-infectious diseases.

    • Types of microscopes used in microbiology.

Types and Characteristics of Micro-organisms

General Characteristics

  • Micro-organisms are classified based on:

    • Cellular components

    • Morphology (size and shape)

    • Means of locomotion

    • Reproduction methods

  • Microbial Nutrition:

    • Free-living microbes obtain nutrients from their environment.

    • Parasites depend on a host to live, potentially causing harm.

  • Definitions of Key Terms:

    • Micro-organism: Organisms too small to be seen without magnification, including bacteria, viruses, fungi, protozoa, and certain animals.

    • Fungi: Eukaryotic organisms that decompose organic matter or form symbiotic relationships with plants; can also be pathogenic.

    • Infectious diseases: Communicable diseases spread from one person to another, caused by microbes.

    • Non-infectious diseases: Diseases that are not transmissible between individuals; arise from factors like age or lifestyle.

    • Protozoans/Protists: Unicellular aerobic eukaryotes, significant for number and diversity in ecosystems, feeding on cells.

    • Parasites: Micro-organisms that depend on a host for nutrition.

    • Host: Organism providing sustenance to a parasite.

    • Pathogen: Infectious agent causing disease.

Types of Pathogenic Micro-organisms

Bacteria

  • Unicellular prokaryotic organisms that can cause various diseases:

    • Examples of bacterial diseases: Tuberculosis, meningitis, food poisoning.

  • Not all bacteria are pathogenic; many support bodily functions as part of normal flora.

Viruses

  • Noncellular entities with a nucleic acid core (either DNA or RNA) enclosed in a protein coat.

  • Classified as micro-organisms but are not considered living organisms.

  • Invade host cells to replicate, causing diseases such as:

    • Influenza

    • Measles

    • Mumps

    • HIV

    • COVID-19

Protozoans (Protists)

  • Unicellular eukaryotes that are abundant in diversity and biomass.

  • Traditionally categorized by locomotion (e.g., flagella).

  • Diseases caused by protozoans include:

    • Dysentery

    • Malaria

    • Sleeping sickness (African trypanosomiasis)

Fungi

  • Include mushrooms, molds, and yeast, all with eukaryotic cells and true nuclei.

  • Nutrient acquisition via absorption from the environment.

  • Fungal diseases in humans include:

    • Asthma

    • Athlete’s foot

    • Ringworm

    • Lung infections

    • Bloodstream infections

Animals (Helminths)

  • Parasitic worms visible to the naked eye, affecting human health.

  • Types include:

    • Flatworms (tapeworms): Live in intestines.

    • Roundworms: Can inhabit gastrointestinal tract and lymphatic system.

Infectious vs. Non-Infectious Diseases

Definitions

  • Disease: A condition disrupting normal functioning of cells and organs.

  • Infectious Diseases: Conditions caused by pathogenic organisms; spread through:

    • Direct contact (skin-to-skin, sexual contact).

    • Contaminated surfaces.

    • Body fluids (blood, saliva).

    • Respiratory droplets or airborne particles.

    • Examples: Cholera, chickenpox, COVID-19.

Non-Infectious Diseases

  • Conditions existing within an individual, usually non-communicable.

  • Caused by factors like:

    • Age

    • Nutritional deficiencies

    • Gender

    • Lifestyle choices.

  • Examples: Diabetes, cancer, asthma.

Micro-scopes in Microbiology

  • Invented in the 1600s; crucial for microbiological studies.

  • First Microscope: Built by Anton Van Leeuwenhoek, led to discoveries of microbes and blood cells.

  • Type Categorization: Based on physical principles and imaging methods.

Types of Microscopes

  1. Light Microscopes

    • Use visible light for imaging.

    • Six varieties:

      • Bright-field microscope

      • Dark-field microscope

      • Phase contrast microscope

      • Fluorescence microscope

      • Confocal scanning laser microscope (CSLM)

      • Differential interference contrast (DIC)

    • Resolution: Depends on the light wavelength, with about 0.5 micrometers for the best light microscopes.

  2. Electron Microscopes

    • Utilize electrons instead of light to form images, enabling magnification up to 150,000 times.

    • Types include:

      • Transmission Electron Microscope (TEM)

      • Scanning Electron Microscope (SEM)

    • Limitations: Requires a vacuum, unsuitable for live cell observation.

Practice Problems

  1. What term is used to describe all disease-causing micro-organisms?
    Answer: C. Pathogen

  2. Which of the following is at the core of every virus particle?
    Answer: A. DNA or RNA

  3. Which microscope achieves the greatest resolution and highest magnification?
    Answer: D. Electron

  4. Which of the following are considered micro-organisms?
    Answer: B. Protozoa, C. Bacteria, D. Fungi

  5. Explain the differences between infectious and non-infectious diseases in your own words.