Groups of Micro Organ..

Introduction to Microbiology

  • Third video in a series introducing microbiology
  • Focus on:
    • Groups of microorganisms
    • Taxonomic hierarchy
    • Three domains of life
    • Naming of microorganisms
    • Characteristics of different groups
    • Sizes of microbes

Roles of Microorganisms

  • Microorganisms have diverse and significant roles:
    • Decomposition of waste
    • Nitrogen and oxygen production
    • Contribution to human health
    • Importance in agriculture
    • Role in pharmaceuticals
    • Food production
  • Ubiquitous Nature of Microbes:
    • Found in various environments:
    • Earth’s crust
    • Polar ice caps
    • Oceans
    • Inside human bodies
  • Definition:
    • Microbes are organisms too small to be seen with the naked eye.

Taxonomy

  • Science of classifying organisms is called taxonomy.
  • Historical Context:
    • Dates back to Aristotle's 'ladder of life' concept, placing humans at the top.
    • Carl Linnaeus:
    • Developed a modern taxonomy based on physical appearances.
    • Classification example:
      • Sheep (mammals) vs. snakes (reptiles).
  • Limitation of Linnaeus' System:
    • Based on physical characteristics, which is limiting for microorganisms due to similarity in appearance.

Classification of Microorganisms

  • Biochemical Characteristics:
    • Used to classify microorganisms through chemical reactions and waste products.
  • Phylogeny:
    • Taxonomic scheme grouped by evolutionary relatedness rather than physical features.
    • Developed by Carl Woese using the 16S rRNA sequence:
    • All organisms have ribosomes; 16S rRNA is a conserved sequence within ribosomes.
    • Relatedness determined by similarity of DNA sequences:
      • Closer sequences indicate closer relationships.
  • Phylogenetic Tree of Life:
    • Three domains:
    1. Bacteria
    2. Archaea
    3. Eukarya
    • Branching points denote common ancestors.
    • Notable finding:
    • Archaea are genetically closer to eukaryotes than bacteria.

Taxonomic Hierarchy

  • Classification Structure:
    • Domains → Kingdoms → Phyla → Classes → Orders → Families → Genuses → Species.
  • Mnemonic for Taxonomic Hierarchy:
    • "Dear King Philip Came Over For Ginger Snaps" to remember the order.
  • Focus on Genus and Species:
    • Scientific naming of organisms is based on these two levels.

Naming Microorganisms

  • Naming convention with examples:
    • Escherichia coli
    • Genus: Escherichia (from scientist Theodore Escherich)
    • Species: coli (found in colon)
    • Abbreviation: E. coli
    • Staphylococcus epidermidis
    • Genus: Staphylococcus (means grape-like, round clumps)
    • Species: epidermidis (found on skin)
  • Importance of Proper Formatting:
    • Genus is capitalized, species is lowercase.
    • When handwriting, underline the scientific name; when typing, italicize.

Prokaryotes vs. Eukaryotes

  • Definition:
    • Prokaryotes: Organisms without a nucleus (bacteria and archaea).
    • Eukaryotes: Organisms with a true nucleus.
  • Emphasis on shared characteristics for grouping:
    • Focus for the semester will be on:
    • Bacteria
    • Fungi
    • Protozoans
    • Helminths
    • Viruses (including prions)

Characteristics of Microorganisms

  • Primary groups and characteristics:
    • Bacteria: Prokaryotic, single-celled.
    • Fungi: Eukaryotic, can be single-celled (yeasts) or multicellular (molds, mushrooms).
    • Protozoans: Eukaryotic, single-celled.
    • Helminths: Multicellular worms.
    • Viruses and Prions: Not composed of cells, so have no cell type.
  • Cell Wall Composition:
    • Bacteria: Peptidoglycan cell wall.
    • Fungi: Chitin cell wall.
    • Protozoans: No cell wall; may have a pellicle.
    • Helminths: No cell wall.
    • Viruses/Prions: No cell wall.

Sizes of Microorganisms

  • Microorganism Measurement:
    • Utilizes the metric system, focusing on micrometers.
    • 1 micrometer = one millionth of a meter.
  • Size Ranges:
    • Average prokaryotic cell: 1-2 micrometers.
    • Average eukaryotic cell: 10-50 micrometers.
    • Prions: Smallest, as they are proteins (considered non-living).
    • Viruses: Typically between 30-1000 nanometers.
    • Bacterial cells: Generally 1-2 micrometers.
    • Unicellular eukaryotes: About 10 micrometers or larger.
    • Multicellular eukaryotes (e.g., worms): Varied size, often visible under a microscope.

Conclusion

  • Review of the lecture's content:
    • Classification of microorganisms.
    • Three domains of life.
    • Importance of proper scientific naming and understanding microbial characteristics.