Microbiology 251: Introduction and Microscopy Notes

General Microbiology Notes

Introduction to Microbiology

  • Definition of Microbiology: Study of microorganisms (microbes), which are very small living things.
  • Microorganism Definition: An organism too small to be seen individually by the naked eye.
  • Size and Visibility: Individual cells require microscopy; colonies can be seen without aid.
  • Scale of Microorganisms: Typically in the micrometer (\mum) or nanometer (nm) range.

Microscopy

  • Problem of Size: Microorganisms are too small to be seen without assistance.
  • Microscopes: Used to increase magnification.
  • Resolution: The minimum distance two points can be apart and still be distinguishable as separate points.
  • Light Microscopes: Use visible light and magnifying lenses, resolving up to 200 nm.
  • Electron Microscopes: Use beams of electrons for much higher resolution.
  • Light vs. Electron Microscopes:
    • Light microscopes use wavelengths of visible light.
    • Electron microscopes use wavelengths of accelerated electrons.
  • Types of Light Microscopy: Bright-Field, Dark-Field, Phase-Contrast, and Fluorescence Microscopy.

What Microbiologists Do

  • Areas of Study:
    • Genetics
    • Physiology
    • Pathogenesis
    • Ecology and interaction with the environment
    • Interactions with other organisms (symbiosis)
  • Potential Applications:
    • Industry
    • Agriculture
    • Medicine

Subfields of Microbiology

  1. Bacteriology: Study of bacteria.
  2. Mycology: Study of fungi.
  3. Parasitology: Study of parasitic protozoa and parasitic worms.
  4. Virology: Study of viruses.

Naming, Describing, and Classifying Microorganisms

  • Necessity: Important for study in the lab, natural environment, or any setting.
  • Defining Species:
    • Eukaryotes: Organisms of different species cannot mate and produce fertile offspring.
    • Bacteria and Archaea: Defined by genetic similarities (97% 16S rRNA homology); definition is challenging due to horizontal gene transfer and rapid evolution.
  • Naming Microorganisms:
    • Always includes genus and species.
    • Italicized.
    • Genus capitalized, species lower case.
    • Genus may be shortened to initial.
    • May include strain designation.
    • Examples: Streptococcus pyogenes (or S. pyogenes), Escherichia coli O157:H7, Physarum polycephalum
  • Describing Microorganisms:
    1. Number of cells: Unicellular vs. Multicellular
    2. Cell type: Prokaryotic vs. Eukaryotic
    3. Size: Microscopic vs. Macroscopic
    • Examples: Bacterial cells (unicellular, prokaryotic, microscopic), parasitic worms (multicellular, eukaryotic, macroscopic).
  • Classifying Microorganisms - Phylogeny of Life:
    • Three domains of life: Bacteria, Archaea, and Eukarya
    • Domain Bacteria: Pathogens, symbiosis, bioremediation, food products
    • Domain Archaea: No known pathogens, many are extremophiles
    • Domain Eukarya: Divided into kingdoms; includes fungi and protists

Taxonomic Classification

  • Order of Taxonomy: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
  • Mnemonic Device: Did King Philip Come Over For Great Spaghetti?
  • Examples:
    • Dog: Domain Eukarya, Kingdom Animalia, Phylum Chordata, Class Mammalia, Order Carnivora, Family Canidae, Genus Canis, Species lupus, Subspecies familiaris
    • Bacterium: Domain Bacteria, Kingdom Eubacteria, Phylum Proteobacteria, Class Gammaproteobacteria, Order Enterobacteriales, Family Enterobacteriaceae, Genus Yersinia, Species pestis Strains: KIM and CO92

Broad Groups of Microorganisms

  1. Bacteria
  2. Archaea
  3. Fungi
  4. Protozoa
  5. Algae
  6. Viruses
  7. Animal Parasites

Characteristics of the 7 Groups

  • Bacteria:
    • Prokaryotes
    • Single-celled
    • Peptidoglycan cell walls
    • Divide via binary fission
    • Derive nutrition from organic or inorganic chemicals or photosynthesis
  • Archaea:
    • Prokaryotes
    • Unicellular
    • Lack peptidoglycan cell walls (protein-based instead)
    • Molecular physiology similar to eukaryotes
    • Often live in extreme environments (extremophiles)
    • No known pathogens
  • Fungi:
    • Eukaryotes
    • Chitin cell walls
    • Absorb organic chemicals for energy
    • Yeasts are unicellular
    • Molds and mushrooms are multicellular
  • Protozoa:
    • Eukaryotes
    • Unicellular generally
    • Absorb or ingest organic chemicals
    • May be motile via pseudopods, cilia, or flagella
  • Algae:
    • Eukaryotes
    • Unicellular or Multicellular
    • Cellulose cell walls
    • Found in freshwater, saltwater, and soil
    • Use photosynthesis for energy
  • Viruses:
    • Acellular
    • Genetic material: DNA or RNA
    • Core surrounded by a protein coat (possibly a membrane)
    • Replicate only inside a host cell
    • Inert outside living hosts
  • Parasitic Animals:
    • Eukaryotes
    • Multicellular animals
    • Cell membranes, no cell wall
    • Not all strictly microorganisms
    • Helminths: parasitic flatworms and roundworms

Microbial Activities and Benefits

  1. Photosynthesis: Converting inorganic carbon into organic carbon using light energy.
  2. Chemical Cycling: Converting nitrogen, sulfur, and phosphorous into usable (organic) forms.
  3. Decomposition: Breaking down organic waste and dead material into simpler compounds (like carbon dioxide).

Benefits of Microbial Activities

  • Agriculture: Microbes benefit plants by providing nitrogen.
  • Bioremediation: Microbes treat sewage and remove toxins from the environment.
  • Food Microbiology: Use microbes to create cheese, beer, and other foods.
  • Industrial Microbiology: Genetic engineering and recombinant DNA tech.
  • Antimicrobials: Some microbes produce antibiotics and antifungals.

Microorganisms and Humans

  • Normal Microbiota: Microbes living in and on our bodies.
  • Diversity: Different regions of the body contain diverse microbial communities.
  • Ratio of Bacterial to Human Cells: Approximately 1.3:1 (recent evidence).

Microorganisms and Disease

  • Pathogens: Some microorganisms cause disease in animals and plants.
  • Infectious Disease: A disease in which pathogens invade a susceptible host.
  • Examples: Smallpox, Influenza, Treponema pallidum (syphilis)

History of Microbiology

  • Antoni van Leeuwenhoek: Created microscopes and observed microorganisms (