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42 Cards in this Set
- Front
- Back
difference between prokaryotes and eukaryotes
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prokaryotes lack membrane-bound organelles
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2 major disease-causing groups of unicellular eukaryotes
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fungi
protozoans |
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4 structures common to all bacteria
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murein (peptidoglycan) cell wall
exoproteins cytoplasmic membrane ribosomes, both free and attached to surface of cytoplasmic memrane |
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characteristics of bacterial endoskeleton
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found in rod-shaped bacteria
homologous to actin cytoskeleton of eukaryotic cells |
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why do bacteria need a murein cell wall?
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to prevent cell lysis:
solute conc in bacterial cytoplasm is much higher than solute conc in bld/ECF of host cell |
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structure of murein cell wall
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1 molecule of murein surrounds the entire cell
peptide component and glycan component: peptidoglycan glycans = polysaccharides individual glycans cross-linked by peptides 4-5 a.a.s long |
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cross-linking
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individual glycans (polysaccharides) of the murein cell wall are cross-linked by peptides 4-5 a.a.s long
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Why are Mycoplasma different from all other bacteria?
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crippled: no murein cell wall
therefore, don't survive in environments without high solute concentrations need to be cultured with osmotic stabilizers, e.g. sucrose |
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significance of exoproteins
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virulence factors
can be secreted from bacterium or remain adhered to the bacterial cell interact with and damage host cell |
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distinguish gram negatives from gram positives
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gram negatives: outer membrane with LPS
gram negatives: no outer membrane; THICK murein wall with teichoic acid |
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teichoic acid
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polysaccharide chains
located in murein cell wall of gram positives diagnostic b/c highly antigenic diagnostic b/c differ from species to species |
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group-specific antigen vs. type-specific antigen
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both are virulence factors in gram positives
group-specific antigen identifies 1 grp of Streptococcus from another (e.g. C polysaccharide of Streptococci) type-specific antigen identifies 1 type of virulence from another (e.g. M protein of group A Strep) |
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name the 6 gram positive organisms
(all the rest are gram negative) |
Streptococcus
Staphylococcus Bacillus Clostridium Corynebacterium Listeria |
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C polysaccharide of Streptococci
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example of group-specific antigen
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M protein
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example of type-specific antigen; major virulence factor of Streptococci
allows subtyping of beta-hemolytic Streptococci |
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characteristics of gram positives
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thick murein cell wall; no outer membrane
teichoic acid polysaccharide chains group-specific antigens, e.g. C polysaccharide of Streptococci type-specific antigens, e.g. M protein of Streptococci |
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characteristics of gram negatives
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bilayer outer membrane with LPS and OM proteins
periplasmic space with periplasmic proteins |
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2 roles of outer membrane proteins
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virulence factors / adhesion to host cell
porins (aqueous channels) |
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periplasmic proteins
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in periplasmic space of gram negatives
enzymes, e.g. beta-lactamases |
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LPS
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lipopolysaccharide in outer membrane of gram negatives
composed of: lipid A endotoxin core polysaccharide O-antigen (=polysaccharide) |
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lipid A
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endotoxin
highly toxic component of LPS in the outer membrane of gram negatives conserved among gram negatives |
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core polysaccharide
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1 component of LPS in outer membrane of gram negatives
common to all gram negatives no known role in pathogenicity |
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O-antigen
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1 component of LPS in outer membrane of gram negatives (=polysaccharide)
variable among gram negatives and therefore diagnostic virulence factor: inhibits phagocytosis |
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name 3 optional structures of bacteria
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pilus
flagellum capsule |
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flagellum
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motility - propeller
not a clear virulence factor H antigen can be used for typing |
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H antigen
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antigenic determinant that makes up subunits of flagella
can be used in typing |
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pilus
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rod-like protein structure
virulence factor: tip of structure is specific for binding and adherence to host found in cytoplasmic membrane (g+) or outer membrane (g-) |
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capsule
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virulence factor: inhibits phagocytosis
large mucoid structure (no organelles) that surrounds cell amost always made of polysaccharide chains mutation causes loss of capsule causes loss of virulence |
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bacterial spores
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metabolically inactive form of bacteria
spore coat prevents toxic elements from entering cell sporulation triggered by environmental cues |
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cytoplasmic changes in sporulation
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water loss
altered composition of DNA and proteins |
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lipid A
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endotoxin
highly toxic component of LPS in the outer membrane of gram negatives conserved among gram negatives |
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core polysaccharide
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1 component of LPS in outer membrane of gram negatives
common to all gram negatives no known role in pathogenicity |
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O-antigen
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1 component of LPS in outer membrane of gram negatives (=polysaccharide)
variable among gram negatives and therefore diagnostic virulence factor: inhibits phagocytosis |
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name 3 optional structures of bacteria
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pilus
flagellum capsule |
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flagellum
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motility - propeller
not a clear virulence factor H antigen can be used for typing |
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H antigen
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antigenic determinant that makes up subunits of flagella
can be used in typing |
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pilus
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rod-like protein structure
virulence factor: tip of structure is specific for binding and adherence to host found in cytoplasmic membrane (g+) or outer membrane (g-) |
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capsule
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virulence factor: inhibits phagocytosis
large mucoid structure (no organelles) that surrounds cell amost always made of polysaccharide chains mutation causes loss of capsule causes loss of virulence |
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bacterial spores
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metabolically inactive form of bacteria
spore coat prevents toxic elements from entering cell sporulation triggered by environmental cues (nutrient deprivation) |
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cytoplasmic changes in sporulation
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water loss
altered composition of DNA and proteins |
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vegetative cell can undergo either _____ or _____
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sporulation (nutrient deprivation) or
germination (nl envt) |
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how do you induce germination of a sporulating cell back to a normal vegetative cell?
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feed the organism
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