Introduction to Microbiology: History and Nomenclature

Discussion Prompt

• Should we use antibacterial cleaning products all over our home?
  • Think about pros and cons before a Zoom discussion.

Types of Microorganisms

• Microbiology: Study of organisms too small to be seen without magnification
  • Examples: bacteria, archaea, protozoans, fungi, helmets, viruses, algae
• Microorganisms Comparisons:
  • Human hair: Brown
  • Helminth (Taneasolium, pork tapeworm): Pink with hooklets
  • Fungus (Aspergillus): Blue
  • Protozoan: Different examples
  • Red blood cell: Relative size comparison
  • Bacteria (e.g., E. coli): ~1x2 micrometers
  • Viruses: Acellular, ultra-microscopic

Historical Context

• Earth: ~4.6 billion years old
• First living organisms: ~3.8 billion years ago
  • First organisms: Unicellular
• Last common ancestor split into:
  • Eukaryotic cells: True nucleus
  • Archaea and Bacteria: Prokaryotic cells, no true nucleus
  • Archaea more closely related to Eukaryotic than Bacteria

Characteristics of Major Microorganisms

Bacteria

• Prokaryotic: No membrane-bound nucleus
• Cell Wall: Peptidoglycan (protein + sugar)
• Unicellular: Single cell organism
• Reproduction: Binary fission (asexual)
• DNA: Circular
• Nutrition:
  • Photosynthetic (autotrophic, e.g., Cyanobacteria)
  • Heterotrophic (consume food)

Archaea

• Prokaryotic: No membrane-bound nucleus
• Cell Wall: Pseudomurin (similar to peptidoglycan)
• Unicellular: Single cell organism
• Reproduction: Binary fission (asexual)
• DNA: Circular
• Adaptations: Extremophiles (thermophiles, halophiles, methanogens)

Fungi

• Eukaryotic: Membrane-bound nucleus
• Cell Wall: Chitin (polysaccharide)
• Nutrition: Heterotrophic (consume food)
  • Many are saprobes (feed on dead decaying matter)
• Organization:
  • Unicellular (e.g., yeasts like Saccharomyces cerevisiae)
  • Multicellular (e.g., molds, mushrooms)
• Reproduction: Sexual or asexual
• DNA: Linear

Protozoans

• Eukaryotic: Membrane-bound nucleus
• Cell Walls: Usually lack
• Nutrition: Heterotrophic
• Unicellular: Single cell organism
• Reproduction: Sexual or asexual
• Movement: Pseudopods, flagella, cilia, or non-motile

Algae

• Eukaryotic: Membrane-bound nucleus
• Cell Wall: Cellulose (polysaccharide)
• Nutrition: Photosynthetic (autotrophic)
• Organization: Unicellular or multicellular
• Reproduction: Sexual or asexual
• Pigments: Green, red, brown

Viruses

• Acellular: Not made of cells, non-living
• Obligate intracellular parasites: Require host to reproduce
• Genetic Material: DNA or RNA but not both
• Structure: Enveloped or naked, with capsid (protein coat)

Multicellular Animal Parasites

• Helminths (worms): Flatworms, roundworms
• Organization: Animals
• Cell Wall: Lack
• Nutrition: Heterotrophic
• Reproduction: Sexual or asexual
• Relevance: Microscopic stages cause diseases

Naming and Classifying Microorganisms

• Taxonomy: Science of classification
• Nomenclature: Naming organisms
• Classification Scheme: Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species
  • Mnemonic: "Do Keep Pots Clean Or Family Gets Sick"
• Example: Cats
  • Domain: Eukarya
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Mammalia
  • Order: Carnivora
  • Family: Felidae
  • Genus: Felis
  • Species: Felis catus

History of Microbiology

Early Microbiology

• Robert Hook (1665): First saw cells in cork, led to cell theory
• Anton van Leeuwenhoek (1673-1723): First to observe living microorganisms
  • Names organisms “animalcules” (rainwater, feces, teeth scrapings)

Spontaneous Generation vs Biogenesis

• Spontaneous Generation: Living organisms from non-living matter
• Biogenesis: Life arises from existing life
• Experiments:
  • Francesco Redi (1668): Meat experiment proves biogenesis
  • John Needham (1745): Flawed experiment suggesting spontaneous generation
  • Lazzaro Spallanzani (1765): Corrected experiment supports biogenesis
  • Louis Pasteur (1861): S-shaped flask experiment; disproves spontaneous generation

Further Advances

• Germ Theory of Disease: Developed through various contributions
• Ignaz Semmelweis (1840s): Advocated hand washing
• Joseph Lister (1860s): Introduced antiseptic surgery
• Robert Koch (1875): Koch’s postulates, proved bacteria cause disease

Vaccination and Antibiotics

• Edward Jenner (1796): Developed first vaccine (cowpox to protect against smallpox)
• Louis Pasteur (1880s): Showed weakened bacteria induce immunity
• Alexander Fleming (1928): Discovered penicillin by accident

Biotechnology and Recent Advances

• Genetic Engineering and Recombinant DNA: Manipulating genetics for new products
• Polymerase Chain Reaction (PCR): Amplifying DNA, revolutionized forensics and diagnostics
• Microbiome Project: Study of human microbiome and its role in health and disease
• Small RNAs (2000s): Regulatory roles in cells, new targets for antimicrobial therapies

Microbes and Their Importance

• Ubiquity: Found everywhere in nature
  • Ex: Earth's crust, polar caps, oceans, bodies of plants/animals
• Importance to Life:
  • Photosynthesis, oxygen production
  • Nutrient cycling: Carbon dioxide, methane contributions
  • Associations with plants and animals for nutrient and protection

Trends in Infectious Diseases

• Emerging Diseases: COVID-19, HIV, Hepatitis C, etc.
• Drug Resistance: Increase in resistant strains, e.g., multi-drug-resistant Gonorrhea
• Connections between Non-infectious Diseases and Microbes: E.g., gastric ulcers, OCD, obesity