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The Microbial World

The Microbial World. Tree of Life. Phylogeny based on 16S ribosomal DNA. Three domains of living organisms Borderline entities Viruses Viroids Prions. Characteristics of Living Organisms. Metabolism Growth Reproduction. Characteristics of Cells.

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The Microbial World

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  1. The Microbial World

  2. Tree of Life • Phylogeny based on 16S ribosomal DNA. • Three domains of living organisms • Borderline entities • Viruses • Viroids • Prions

  3. Characteristics of Living Organisms • Metabolism • Growth • Reproduction

  4. Characteristics of Cells • Cell membrane separates cell from outside • DNA as genetic material • Ribosomes • Basic structural macromolecules • Regulate flow of materials in and out • Reproduce and are the result of reproduction • Require energy

  5. Types of Cells • Prokaryotes • Eukaryotes

  6. Generally eukaryotic cells are morphologically complex and biochemically simple; prokaryotic cells are morphologically simple and biochemically complex

  7. Prokaryotic Cell (Minimal) • No “true” nucleus • No internal membrane bound organelles

  8. Prokaryotic Cell (Maximal) • Inclusions • External structures for attachment, genetic exchange, and movement

  9. Prokaryotic Cell Wall • Unique chemical composition • Protects cell from osmotic lysis • Two major types • Gram positive • Gram negative

  10. Gram Negative Cell Walls

  11. Gram Positive Cell Walls

  12. Structures Exterior to the Wall

  13. Glycocalyx/Capsule • Extracellular polymer • Important in attachment to surfaces - biofilms • Protects against phagocytosis

  14. Biofilm Formation

  15. Pili • Short hairlike appendages projecting from the bacterial cell surface • Composed of protein • Function: • Attachment • Transfer of DNA

  16. Flagella • Long protein (flagellin) appendage • Motility • Structure and function like a propeller • Arrangement of flagella sometimes used in taxonomy/identification of bacteria

  17. Cell Membrane • Fluid Mosaic Model • Phospholipid bilayer with embedded proteins • Regulates transport of substances into and out of the cell

  18. Membrane Transport • Diffusion • Passive/Facilitated Transport • Group Translocation • Active Transport

  19. Internal Structures

  20. Nucleoid • Bacterial chromosome • Single circular piece of DNA • No associated histones

  21. Plasmids • Extrachromosomal small piece of DNA • Independent of chromosome • Code of ancillary functions • Antibiotic resistance • Metal resistance • Catabolic pathways • Self-replicating • Used in genetic engineering

  22. Ribosomes • Combinations of protein and RNA • Essential structures • Function • Protein synthesis • Expression of genetic information • Size differs between prokaryotes and eukaryotes • Prokaryotes: 70S

  23. Inclusions • Magnetosomes • Poly-b-hydroxybutyrate • Sulfur granules • Glycogen • Polyphosphate granules

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