Transcript Comparing Prokaryotic and Eukaryotic Cells

SC246: Microbiology
Fundamentals of Microbiology SC 246
Unit 1 Seminar
Luis Lowe
404-981-6570
[email protected]
AIM account: Luis.Lowe
About Me
 MS Biology and Maters in Public Health
 Work at Centers for Disease Control in Atlanta, Georgia
 Bioterrorism agents
 Molecular Assays, epidemiology, etc…
 Instructor for Microbiology, General Biology and Anatomy
and Physiology
 Science Geek
 Into fitness and nutrition
 Questions
Agenda tonight
 Course overview
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Syllabus, Grading, How to,
Answers for those new to online
Email address should be Kaplan
IMPORTANT NUMBER 877-623-0272
 Eukaryotic vs. Prokaryotic
 What in the world does that mean?
 Bacteria
 Walls
 Gram stains
 Science center tour at 8:45
 Questions
Prokaryotic –Eukaryotic Cells
 Comparing Prokaryotic and Eukaryotic Cells
 Prokaryote comes from the Greek words for
prenucleus.
 Eukaryote comes from the Greek words for
true nucleus.
 What do the terms Prokaryotic and
Eukaryotic mean? What are some of the major
differences between Prokaryotic and
Eukaryotic cells?
Prokaryote
 One (usually) circular
chromosome, not in a
membrane
 No membrane-enclosed
organelles
 Peptidoglycan cell walls
(usually)
 Binary fission
Eukaryote
• Paired chromosomes,
in nuclear membrane
• Organelles
• Simple cell walls (IF
present)
• Mitosis
Question to think about?
 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?
Gram stain
• What is it? What is it used for?
• 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. What does that mean?
• Most, but not all, bacteria can be stained using this method
• Which one(s) can’t.
• Why does it stain differently?
• Why is it a fundamental part of identifying bacteria? What are
the major differences between Gram negative and Gram
positive cells?
Gram Stain Mechanism
 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
Figure 4.13b, c
Differential Stains: Gram Stain
Figure 3.11b
Gram +
Streptococcus Pyogenes
Other clinically relevant Gram +?
(What is strep pyogenes?)
Gram-positive cell walls
 Thick peptidoglycan
 Teichoic acids
 In acid-fast cells,
contains mycolic acid
Gram Stain Anthrax
Gram  Spirillum volutans
(harmless bacteria)
Other clinically relevant
Gram -?
Gram-Negative Outer Membrane
 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
Something to think about?
 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?
KU Science Center Tour
 Go to the following link
 http://khe2.adobeconnect.com/kusc_tour/
 Afterwards, you are free to go
 Email with any questions you may have.
Questions??
References
 Tortora, G., Funke, B., & Case, C. (2007). Microbiology: An
Introduction (8th ed.). San Francisco, CA: Pearson.
Peptidoglycan
 Polymer of disaccharide
N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM)
 Linked by polypeptides
Figure 4.13a
Gram-Positive cell walls
 Thick layer of peptidoglycan
Figure 4.13b
Gram-Negative Outer Membrane
Figure 4.13c