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Chapter 3: Microscopy and Cell Structure

Chapter 3: Microscopy and Cell Structure. Important Point:. If you are having trouble understanding lecture material: Try reading your text before attending lectures. And take the time to read it well!. Typical Bacterial Shapes.

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Chapter 3: Microscopy and Cell Structure

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  1. Chapter 3:Microscopy andCell Structure

  2. Important Point: If you are having trouble understanding lecture material: Try reading your text before attending lectures. And take the time to read it well!

  3. Typical Bacterial Shapes Also Pleomorphic Bacteria, which vary in their shape(e.g., Corynebacterium).

  4. Typical Bacterial Arrangements streptococci sarcina staphylococci

  5. ProkaryoticCell Structures

  6. Typical Prokaryotic Cell

  7. Cytoplasmic Membrane • Movement across membrane for many substances is controlled by membrane proteins. • Escherichia coli has >200 membrane proteins. • Many of these proteins are involved in transport across membranes. • Others of these proteins allow a bacterium to sense its surrounding environments(e.g., as in chemotaxis). • Movement is via: • Simple Diffusion (including osmosis) • Facilitated Diffusion (with concentration gradient & no energy expended) • Active Transport (against concentration gradient & energy expended)

  8. Simple Diffusion -- Osmosis solute molecules/ions

  9. Cytoplasmic Membrane

  10. Protein-Mediated Transport

  11. Active Transport

  12. The Prokaryotic Cell Wall

  13. The Prokaryotic Cell Wall In some cases recognized by host immune system. Determines cell shape. Prevents osmotic lysis. Target for antibiotics. In Bacteria, composed of Peptidoglycan. Part of cell envelope.

  14. Gram-Pos vs. Gram-Neg.

  15. Gram-Positive Cell Envelope

  16. Gram-Negative Cell Envelope endotoxin cell wall

  17. Gram-Negative Cell Envelope LPS: Protection from antibiotics such as penicillin plus against certain toxins. Periplasm: Site of preliminary nutrient degradation.

  18. Carbohydrate has negative charge and provides protection against some antibiotics & some toxins (e.g., detergents). Lipopolysaccharide (LPS) Lipid A = Endotoxin

  19. Mycoplasma lack Cell Walls Note: Pleomorphic Mycoplasma pneumoniae causes “Walking Pneumonia”

  20. Protection (e.g., Streptococcus pneumoniae from phagocytosis) Glycocalyx Attachment (e.g., Streptococcus mutans causing dental plaques)

  21. Capsule Staining Capsules are more regular and gelatinous. Slime Layers are less regular and more diffuse.

  22. Bacteria Flagella (plural)

  23. Flagellar Arrangements Polar Flagellum e.g., E. coli also “atrichous”

  24. Chemotaxis Also Phototaxis, etc.

  25. Pili (sing. Pillus)

  26. Fimbriae (a kind of pilli) Tips are Adhesins, used to adhere, e.g., to animal tissues

  27. Closed Circular Chromosome Also Plasmids, which are smaller, circular pieces of DNA. Plasmids usually encode expendable functions, e.g., antibiotic resistance.

  28. Ribosomes: Sites of Translation On order of 10,000 per cell!

  29. Form inside of vegetative cells (hence “endo”). Endospores Characteristic of many soil bacteria, e.g., Bacillus spp. & Clostridium spp. Highly resistant to heat, U.V., desiccation, etc.

  30. Link to Next Presentation

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