Mon'

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Mon. Wed., Jan. 28 30, 2008

• Koch essay. Turn in Wednesday. Further
  information on the CPR system will be available
  next week.
• We will spend some time today reviewing.

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Opportunities

• Extra Credit 2 points on a lab report
• Animal Dreams Discussion Feb. 22, noon-1 TTC
  5740
• Peace Jam Jan. 31 330-5 p.m. TTC 4230
• Student Success Center Life Resources Workshops
• Lifestyle Communication Jan. 29 noon-1 TTC
  Student Commons Forum
• The Secret video/viscussion Jan. 30, 1230-230
  p.m. TTC Student Commons Theater
• Steve Spiece (re setting up medical care
  facilities in Iraq)

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(No Transcript)
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Review Dichotomous Keys

• Overview
• Sample with Flowchart
• Practice

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Preview of Coming Attractions

• Using a dichotomous key to identify a bacterial
  species Differential stains.
• Notes
• Mordant a reagent that makes a dye permanent,
  so that it is not washed out
• Gram stains are the differential stains well be
  doing next week.
• In the following animation, they first do
  something, and then flash the words for whats
  been done.
• Caution Unlike in animation, do NOT touch
  dropper to specimen or slide!
• No need to memorize Preview

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Review - Nucleic Acid Structures

• Compare/contrast the structure of RNA and DNA.
• Consider the sugar the number of nucleotide
  strands, the four nucleic acids in each
• (Lets look at the next few slides, and draw! ?
  )
• (Yes, you CAN DRAW! Have fun!)

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Ribose and Deoxyribose
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Nucleotide
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In the next slide, note

• Cytosine and guanine (C and G) pair, because each
  is capable of participating in three hydrogen
  bonds.
• Adenine and thymine (A and T) pair, because each
  is capable of participating in two hydrogen bonds.

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Double Helix
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ANIMATIONS

• Transcription Overview
• Transcription Process
• Translation Overview
• Translation Process
• Translation Genetic Code

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What is the structure of the ribosome?

• Show overhead.
• Draw. ?
• Prokaryotic versus eukaryotic.

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What are some differences between eukaryotic and
prokaryotic

• Chromosomes
• Ribosomes

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What are some differences between eukaryotic and
prokaryotic

• Chromosomes
• Ribosomes

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Chromosome

• 1000 times length of cell
• Circular
• Double stranded
• Supercoiled

An E. coli cell which was very carefully lysed
and proteins removed. The cell was in the center.
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Nucleoid
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B. Plasmid

• Small extra loop of chromosome/genetic material.
• 5 - 100 genes (few thousand bases).
• Not critical to oridinary everyday functions,
  but
• confer antibiotic resistance.
• confer virulence factors.
• promote conjugation.

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C. Ribosomes

• Ribose sugar body. (Review the molecular
  structure of RNA.)
• Cell may contain thousands of ribosomes
• composed of a small (30S) subunit and a large
  (50S) subunit.
• Less dense than eukaryotic ribosomes.

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Molecular Structure of Ribosomes
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2 Subunits of Ribosomes
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Ribosome site of protein synthesis

• Composed of rRNA and proteins.
• 2 subunits, 30S 50S.
• Bacterial 70S total eukaryotic 80S total

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Antibiotic Mechanisms

• Mechanism Overview
• Inhibit cell wall synthesis.
• Disrupt plasma membrane.
• Inhibit protein synthesis.
• Inhibit metabolic pathway.
• Inhibit DNA/RNA synthesis.
• Well focus on only a few of these today.

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Mechanism 1 Inhibit Cell Wall Synthesis

• Penicillin and penicillin relatives, such as
  cephalosporin, block formation of peptide
  cross-links in the peptidoglycans layers in
  bacterial cell walls ?
• weakened cell walls ?
• lysis

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Mechanism 2Disrupt Plasma Membrane

• Polymixins attach to phospholipids in bacterial
  cytoplasmic membranes ?
• Lysis
• Note Polymixins can be used only topically (on
  the skin, which has a dead outer layer), because
  polymixins also affect eukaryotic membranes.

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Mechanism 3Inhibit Protein Synthesis

• Tetracycline blocks docking sites of t-RNA ?
  prevents amino acids from being added.
• Chloramphenicol blocks formation of peptide
  bonds between amino acids.
• Macrolides, such as erythromycin block m-RNA
  movement through the ribosome.
• Aminoglycosides, such as streptomycin change
  the shape of the smaller 30S ribosome subunit ?
  misreading of RNA insertion of incorrect amino
  acids.

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Mechanism 4Inhibit Metabolic Pathways

• Sulfonamides (sulfa drugs) block a step in folic
  acid synthesis.
• They do this by competing with PABA (para-amino
  benzoic acid).
• ? Deprived of its ability to manufacture folic
  acid, the microbe cannot reproduce.
• Folic acid is also known as vitamin B9.

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Mechanism 5Inhibit DNA/RNA Synthesis/Activity

• Quinolones fluoroquinolones block DNA gyrase.
• Rifampin binds binds more readily to RNA
  polymerase in prokaryotes than eukaryotes ?
  blocks transcription.

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Selective Toxicity

• What is the mode or mechanism of action of
  tetracycline?
• How is this selectively toxic?

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Identify other antibiotics that have modes of
action similar to that of tetracycline
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What is the mode of action of the quinolones or
the fluoroquinolones?

• Are these drugs selectively toxic?

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E. Storage Granules, or Inclusion Bodies

• Bacterias way of storing nutrients.
• Vary in size and number.
• Most often are CHO, lipid and PO4.
• Staining of some granules aids in identification.

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Corynebacterium diphtheriae

• Gram positive bacilli.
• History 30-50 mortality.
• Current 10 cases/yr in U.S.
• Bacteria acquires a recipe for a toxin from a
  virus.
• Toxin inhibits protein synthesis.
• Tx and prevention.

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Pseudomembrane
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Corynebacterium diphtheria
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Neutralization by Antibody

• Antibody Neutralization Video

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Neutralization by Antibody
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Cell Envelope

• Cell membrane.
• Cell wall.
• Glycocalyx.

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Cell Envelope

• Cell membrane
• All bacteria have a membrane.
• Cell wall
• Some lack cell walls.
• Some have walls that stain with Gram stain
• Gram positive (purple).
• Gram negative (pink).
• Some have walls that stain with acid fast stain
  (red positive).
• Glycocalyx.

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Cell Membrane

• Structure
• Phospholipid bilayer.
• Embedded proteins.
• Fluid mosaic model.
• Sterols
• Mycoplasma
• M. pneumoniae

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Do all bacteria have cell walls?

• Identify an example of a cell that is Gram
  negative and Gram positive.
• Where does the genus Mycoplasma fit?
• Where does the genus Mycobacterium fit? (3)

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Cell Membrane Structure
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Membrane Structure
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Membrane Function

• Membrane Structure and Function.
• Selectively permeable.
• Scientific Method diffusion osmosis.

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Solutions

• Isotonic
• Hypotonic
• Hypertonic

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Cell Walls

• Contain unique molecule called peptidoglycan
• What are the subunits of the glycan portion of
  the peptidoglycan?
• From what dietary precursor are these molecules
  derived? (4)

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Peptidoglycan
NAM O NAG N-acetylmuramic acid N-acetylgluco
samine
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Peptidoglycan
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Peptidoglycan
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Gram Positive
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Gram Negative
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Comparison
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How are Gram negative cell walls different from
Gram positive cell walls? (5)
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• How is the outer membrane different from the cell
  membrane?
• What layer of the cell envelope is the outer
  membrane considered? (5)

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Lipopolysaccharide

• Phospholipid

• lipopolysaccharide

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Differential Stains

• Gram Stain
• http//pathmicro.med.sc.edu/fox/gram-st.jpg
• http//www.opt.pacificu.edu/ce/catalog/13036-AS/Fi
  g201.jpg
• http//www.search.com/reference/Gram-positive

• Acid Fast Stains
• http//www.bact.wisc.edu/themicrobialworld/acid-fa
  stbacilli.jpg
• http//www.lung.ca/tb/images/full_archive/108_baci
  llus.jpg

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1. What is the primary stain for Gram stain?
2. What color will Gram positive cells be after
the application of this stain? 3. What color
will Gram negative cells be after the application
of this stain? (7)
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What is the mordant for Gram stain? What color
will Gram positive cells be after the application
of the mordant? What color will Gram negative
cells be after the application of the mordant?
(8)
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What is the decolorizer for Gram stain? What
color will Gram positive cells be after the
application of the decolorizer? What color will
Gram negative cells be after the application of
the decolorizer? (9)
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What is the counterstain for Gram stain? What
color will Gram positive cells be after the
application of the counterstain? What color will
Gram negative cells be after the application of
the counterstain? (10)
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What is the Gram stain of Mycobacterium? Why?
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What is the Gram stain of Mycoplasma? Why?