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Essentials of Microbiology: History and Types

Apr 18, 2025

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Introduction to Microbiology: History and Nomenclature

Key Questions

  • Should we use antibacterial cleaning products all over the home?
    • Discuss pros, cons, and specific situations.

Microbiology Overview

  • Definition: Specialized area of biology dealing with organisms too small to be seen without magnification.
  • Microorganisms Examples: Bacteria, archaea, protozoans, fungi, helminths, viruses, algae.

Size Comparison

  • Human hair, helminths (e.g., tapeworm), fungi (e.g., Aspergillus), protozoans relative to bacteria and viruses.

Microbial Commonalities and Differences

  • Microbes have shaped earth's habitat for billions of years.
  • Earth Formation: ~4.6 billion years ago, first life ~3.8 billion years ago.

Types of Cells

  • Eukaryotic Cells: Have a membrane-bound nucleus.
  • Prokaryotic Cells: Include archaea and bacteria, no true nucleus.
  • Archaea: More closely related to eukaryotic cells than bacteria.

Characteristics of Different Microorganisms

Bacteria

  • Prokaryotic: Lack membrane-bound nucleus.
  • Cell Wall: Made of peptidoglycan (protein + sugar).
  • Unicellular: Reproduction via binary fission (asexual).
  • DNA: Circular.
  • Energy: Photosynthetic (autotrophic) or heterotrophic.

Archaea

  • Prokaryotic: Similar to bacteria but with distinct cell wall (pseudo-murin).
  • Extremophiles: Love extreme environments (e.g., thermophiles, halophiles).
  • Reproduction: Binary fission, circular DNA.

Eukaryotic Organisms

Fungi

  • Eukaryotic: Cells have membrane-bound nucleus.
  • Cell Wall: Made of chitin (polysaccharide).
  • Heterotrophic: Consume food, often saprobic.
  • Forms: Unicellular (yeast) and multicellular (molds, mushrooms).
  • Reproduction: Sexual or asexual.
  • DNA: Linear.

Protozoans

  • Eukaryotic: Lack cell walls.
  • Heterotrophic, Unicellular.
  • Reproduction: Sexual or asexual.
  • Movement: Pseudopods, flagella, cilia, some non-motile.

Algae

  • Eukaryotic: Cell wall made of cellulose.
  • Photosynthetic & Autotrophic.
  • Forms: Unicellular or multicellular.
  • Reproduction: Sexual or asexual.

Viruses

  • Acellular: Not made of cells, considered non-living.
  • Replication: Obligatory intracellular parasites.
  • Structure: DNA or RNA, capsid (protein coat), possible envelope.

Helminths

  • Large Parasites: Flatworms, roundworms.
  • Reproduction: Sexual or asexual.
  • Microscopic Stages: Study due to disease-causing potential.

Microorganisms in Our Lives

Importance

  • Microbes are ubiquitous and essential for life.
  • Photosynthesis Contribution: Photosynthetic microbes produce ~70% of Earth's oxygen.
  • Environmental Impact: Affect soil, water, and atmospheric composition.

Human Use

  • Biotechnology: Genetic engineering, recombinant DNA technology.
  • Bioremediation: Oil spill clean-up, genetic modification of organisms.
  • Health: Antibiotics, vaccines.

Trends in Microbial Diseases

  • Emerging Diseases: COVID-19, AIDS, Zika.
  • Antibiotic Resistance: Increasing problem.
  • Non-Infectious Disease Links: Some previously non-infectious diseases have microbial components (e.g., ulcers).

Nomenclature and Classification

Taxonomy

  • Definition: Science of classifying living things.
  • Binomial Nomenclature: Genus (capitalized) and species (lowercase).

Classification Hierarchy

  • Domain: Broadest category.
  • Kingdom: More specific categories below domain.
  • Phylogenetic Trees: Show evolutionary relationships.

History of Microbiology

Early Discoveries

  • 1665 Robert Hooke: First observed cells.
  • 1673-1723 Anton van Leeuwenhoek: First observed living microorganisms.

Spontaneous Generation vs. Biogenesis

  • Spontaneous Generation: Life from non-living matter.
  • Biogenesis: Life from pre-existing life.
  • Key Experiments: Redi's meat experiment, Needham's broth, Spallanzani's experiment, Pasteur's S-shaped flask experiments.

Golden Age of Microbiology (1857-1914)

  • Louis Pasteur: Disproved spontaneous generation, developed pasteurization.
  • Ignaz Semmelweis & Joseph Lister: Advocated for handwashing and surgical antisepsis.
  • Robert Koch: Developed Koch's postulates, germ theory of disease.

Advances in Vaccination

  • Edward Jenner: Developed smallpox vaccine using cowpox.
  • Alexander Fleming: Discovered penicillin.

Recent Advances

Molecular Biology

  • Restriction Enzymes: Discovery enabled genetic engineering.
  • Polymerase Chain Reaction (PCR): Amplified small DNA samples.
  • Human Microbiome Project: Explored the roles of human-associated microbes.

This summary covers the essential points discussed in the lecture, suitable for review and study purposes.

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