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SC246: M ICROBIOLOGY Unit 1 Seminar. What do the terms Prokaryotic and Eukaryotic mean? What are some of the major differences between Prokaryotic and.

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Presentation on theme: "SC246: M ICROBIOLOGY Unit 1 Seminar. What do the terms Prokaryotic and Eukaryotic mean? What are some of the major differences between Prokaryotic and."— Presentation transcript:

1 SC246: M ICROBIOLOGY Unit 1 Seminar

2 What do the terms Prokaryotic and Eukaryotic mean? What are some of the major differences between Prokaryotic and Eukaryotic cells?

3 P ROKARYOTIC C ELLS Comparing Prokaryotic and Eukaryotic Cells Prokaryote comes from the Greek words for prenucleus. Eukaryote comes from the Greek words for true nucleus.

4 One (usually) circular chromosome, not in a membrane No membrane-enclosed organelles Peptidoglycan cell walls (usually) Binary fission P ROKARYOTE E UKARYOTE Paired chromosomes, in nuclear membrane Organelles Simple cell walls (IF present) Mitosis

5 From an evolutionary prospective, Prokaryotic cells are much less complex than Eukaryotic cells. It seems that we wouldn’t have much of a problem fighting them off, right? However, this is obviously not the case. Offer an explanation for this. WHY do you think we still get infections and illnesses?

6 What is the Gram stain, and why is it a fundamental part of identifying bacteria? What are the major differences between Gram negative and Gram positive cells?

7 G RAM STAIN The Gram stain was developed by Christian Gram in 1884 Primary stain of identification in microbiology lab Used to classify bacteria as either gram positive or gram negative Most, but not all, bacteria can be stained using this method

8 Staining procedure: 1.Crystal violet and Gram’s iodine: Primary stain 2. Stain is decolorized with 95% ethanol 3. Counterstain: Safranin 4. Water rinse Gram + retain CV and remain purple Gram – retain safranin * Based on cell physiology G RAM S TAIN M ECHANISM

9 D IFFERENTIAL S TAINS : G RAM S TAIN Figure 3.11b

10 S TREPTOCOCCUS PYOGENES G RAM +

11 G RAM - Spirillum volutans (harmless bacteria)

12 Polymer of disaccharide N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM) Linked by polypeptides P EPTIDOGLYCAN Figure 4.13a

13 Figure 4.13b, c

14 Thick peptidoglycan Teichoic acids In acid-fast cells, contains mycolic acid G RAM - POSITIVE CELL WALLS G RAM - NEGATIVE CELL WALLS Thin peptidoglycan No teichoic acids Outer membrane

15 G RAM -P OSITIVE CELL WALLS Figure 4.13b Thick layer of peptidoglycan

16 Lipopolysaccharides, lipoproteins, phospholipids. Forms the periplasm between the outer membrane and the plasma membrane. Protection from phagocytes, complement, antibiotics. O polysaccharide antigen, e.g., E. coli O157:H7. Lipid A is an endotoxin. Porins (proteins) form channels through membrane G RAM -N EGATIVE O UTER M EMBRANE

17 Figure 4.13c

18 The medical and scientific communities use their knowledge of Prokaryotic cells to target infectious microbes and clear out infections. Given just what you have learned so far, how do you think they might go about this?

19 Q UESTIONS ??

20 R EFERENCES Tortora, G., Funke, B., & Case, C. (2007). Microbiology: An Introduction (8th ed.). San Francisco, CA: Pearson.


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