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20 Cards in this Set
- Front
- Back
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Cocci
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Spherical
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Bacilli
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Rod-shaped
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Spirochetes
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Spiral-shaped
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Vibrios
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Curved rod shaped
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Cytoplasmic membrane
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Standard lipid bilayer
Many TM receptors Detection of environment Permeable to water --> subject to high osmotic pressures (cell wall protects) |
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Cell wall
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Protects against osmotic pressure
Provides shape (cocci, bacilli, etc.) Peptidoglycan: sugar backbone + peptides crosslinked |
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Gram stain: process
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1. Stain with aqueous blue dye (crystal violet)
2. Treat with iodine to precipitate the dye 3. Wash with organic solvent (ethanol) 4. Counter stain with red dye |
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Positive gram stain
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Retains the first dye
Organic solvent doesn't wash it off Stains purple Ex. bacillus anthracis |
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Negative gram stain
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First dye washes off
Retains the second, red dye Colorless until second stain |
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Exceptions for gram staining
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1. Mycobacteria: special envelope
2. Mycoplasma: no cell wall 3. Spirochetes: too thin 4. Obligate intracellular pathogens |
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Gram positive bacteria: structure
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Cytoplasmic membrane
Surrounded by thick cell wall of peptidoglycan Teichoic acids with negative charge contribute to rigidity (Extend down to CM = lipoteichoic acids) |
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Gram negative bacteria: structure
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Inner membrane (cytoplasmic membrane)
Periplasm Thin cell wall Outer membrane (connected to thin cell wall via lipoprotein) Outer membrane covered with LPS (endotoxin) |
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LPS
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Inner to outer
Lipid A = endotoxin; two sugars with fatty acids hanging off; Mg2+; can cause shock Core polysaccharide Outer repeating O-antigen subunits |
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S layer
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External structure
2D sheet of self-polymerizing glycoprotein Coat of armor Difficult for complement or antibodies to target |
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Capsule
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External structure
Usually polysaccharide slippery- difficult for phagocytes to grab on and engulf Protect against host immune sys (T cell indep) |
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EPS
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Exopolysaccharide (glycocalyx)
Attachment mechanism Makes sticky- onto things like catheters and medical equipment Can have EITHER capsule or EPS |
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Pili
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AKA fimbriae
Attachment mechanism- other cells, eukaryotic host, other bacteria Hair-like appendages |
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Flagella
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Locomotion
Very long: longer than cell body Motor at base acts like propeller Swim toward food; away from toxic material; localization |
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Locomotion
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Grappling hooks: type IV pili
Caterpillar tracks (bulldozer) Jets (squirt sugar out back to push forward) Propellers (swim)- flagella Internal balloon (not flagella)- gas vvesciles |
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Surface antigens
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Ex. H, K, O antigens
Nothing to do with ability to cause disease; indicates a particular combination of antigen structures unique to that bacteria |
