Intro to Microbiology Study Notes

Lecture 1: Intro to Microbiology

Date: September 3, 2025
Chapters: 1.1 - 1.3

Outline

  • Introduction, Syllabus, Tips for Success

  • Chapter 1.1: Intro to Microbiology

  • Chapter 1.2: Taxonomy

Chapter 1.1: Intro to Microbiology

  • Microbiology:

    • Definition: The study of microorganisms or microbes, which are very small organisms.

    • Most microorganisms cannot be seen without a microscope.

  • Microorganisms/Microbes:

    • Description: Microorganisms are very small entities, often requiring a microscope for visibility.

    • Historical Usage: Humans have utilized microorganisms prior to understanding or even observing them.

    • Example: Yeast fermentation produces ethanol and carbon dioxide.

    • Figure 1.3:

      • Left: Microscopic view of Saccharomyces cerevisiae (yeast).

      • Middle: Yeast metabolizing carbohydrates in flour.

      • Right: Carbon dioxide produced during fermentation causes bread to rise.

Early Notions of Disease

  • Ancient Greeks' Understanding:

    • Attributed diseases to “bad air” (Latin: mal aria).

    • Key Figures:

    • Hippocrates: Known as the father of Western medicine; proposed that diseases had natural causes originating from patients or environmental factors.

    • Thucydides: Regarded as the father of scientific history; he demonstrated evidence-based reasoning about disease transmission, notably observing that the Athenian plague did not re-infect caregivers.

The Birth of Microbiology

  • Antonie van Leeuwenhoek (1632-1723):

    • Contributions: Manufacturer of simple microscopes for studying fabrics.

    • Discoveries: First to observe microorganisms or “wee little beasties” in water.

    • Achievements: Constructed over 250 microscopes capable of magnification up to 300 times.

Early Microbiologists

  • Louis Pasteur:

    • Contribution: Identified fermentation as a process caused by microorganisms, notably in wine, beer, bread, and cheese production.

    • Pasteurization: Developed a technique to kill microorganisms to reduce spoilage in food and beverages.

    • Vaccines: Notable for developing the rabies vaccine.

  • Robert Koch:

    • Research: Identified specific microbes that caused particular diseases.

    • Bacillus anthracis → Anthrax

    • Vibrio cholera → Cholera

    • Mycobacterium tuberculosis → Tuberculosis

Chapter 1.2: Taxonomy

  • Taxonomy Definition:

    • The classification, description, identification, and naming of living organisms.

  • Carolus Linnaeus (1758):

    • Known for Linnaean taxonomy, separating organisms into hierarchical categories:

    1. Kingdom

    2. Phylum

    3. Class

    4. Order

    5. Family

    6. Genus

    7. Species

    • Example of Kingdom-Phylum-Class-Order-Family-Genus-Species hierarchy:

    • Humans:

      • Kingdom: Animalia

      • Phylum: Chordata

      • Class: Mammalia

      • Order: Primates

      • Family: Hominoidea

      • Genus: Homo

      • Species: sapiens

  • Evolutionary Taxonomy:

    • More akin organisms show greater similarity and hence closer evolutionary relationships.

  • Ernst Haeckel (1866):

    • Proposed four kingdoms:

    • Animalia

    • Plantae

    • Protista (unicellular organisms)

    • Monera (unicellular, no nucleus)

  • Robert Whittaker (1969):

    • Suggested a fifth kingdom:

    • Fungi

  • Viruses: Uncertain classification within traditional taxonomy systems.

Modern Taxonomy

  • Carl Woese and George Fox (1977):

    • Developed a tree of life based on genetic similarities, particularly using small subunit ribosomal RNA (rRNA).

    • Identified Archaea as a distinct domain, separate from Bacteria and Eukarya.

  • Implications:

    • Archaea shown to be more closely related to humans than to bacteria, interconnecting domains of life on a genetic basis.

Naming Microbes

  • Binomial Nomenclature:

    • A two-part formal naming system for organisms, combining genus and species within italicized format.

    • Format: Genus species

      • Examples:

      • Haloquadratum walsbyi

      • Homo sapiens

      • Escherichia coli (E. coli)

Types of Microorganisms

  • Units of Length in Microbiology:

    • Metric Equivalent Conversions:

    • Meter (m) = 1 m

    • Decimeter (dm) = 0.1 m

    • Centimeter (cm) = 0.01 m

    • Millimeter (mm) = 0.001 m

    • Micrometer (µm) = 1 × 10^{-6} m

    • Nanometer (nm) = 1 × 10^{-9} m

  • Prokaryotic Microorganisms:

    • Bacteria:

    • Ubiquitous organisms found in diverse environments, including within and on humans.

    • Some bacterial strains may be pathogenic, causing diseases.

    • Shape Variations:

      • Coccus: Round

      • Bacillus: Rod-shaped

      • Vibrio: Comma-shaped

    • Archaea:

    • Thrive in extreme conditions (e.g., hot springs, acidic environments).

    • Some archaea exist within the human microbiome, typically non-pathogenic.

  • Eukaryotic Microorganisms:

    • Protists:

    • An informal group consisting of organisms that are not classified as animals, plants, or fungi.

    • Subcategories: Protozoa and Algae

    • Algae contribute significantly to consumer product ingredients, such as cosmetics and food.

    • Fungi:

    • Can be unicellular (yeast) or multicellular (mushrooms, molds).

    • Fungal structures include hyphae (long threads), pseudohyphae (budding cells), and mycelium (tangled masses of hyphae).

    • Helminths:

    • Multicellular parasitic worms, visible without a microscope.

    • Example of transmission: Guinea worm larvae found in contaminated drinking water.

  • Other Microbes:

    • Viruses:

    • Acellular entities consisting of proteins and either DNA or RNA.

    • Viruses infect host cells to reproduce and spread.

    • Examples: Coronaviruses and Ebolavirus, both noted for their pathogenic traits and capabilities.