bacterial anatomy and physiology
Terms
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- difference between prokaryotes and eukaryotes
- prokaryotes lack membrane-bound organelles
- 2 major disease-causing groups of unicellular eukaryotes
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fungi
protozoans - 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 - characteristics of bacterial endoskeleton
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found in rod-shaped bacteria
homologous to actin cytoskeleton of eukaryotic cells - 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 - 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 - cross-linking
- individual glycans (polysaccharides) of the murein cell wall are cross-linked by peptides 4-5 a.a.s long
- 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 - 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 - 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 - 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 - 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) -
name the 6 gram positive organisms
(all the rest are gram negative) -
Streptococcus
Staphylococcus
Bacillus
Clostridium
Corynebacterium
Listeria - C polysaccharide of Streptococci
- example of group-specific antigen
- M protein
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example of type-specific antigen; major virulence factor of Streptococci
allows subtyping of beta-hemolytic Streptococci - 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 - characteristics of gram negatives
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bilayer outer membrane with LPS and OM proteins
periplasmic space with periplasmic proteins - 2 roles of outer membrane proteins
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virulence factors / adhesion to host cell
porins (aqueous channels) - periplasmic proteins
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in periplasmic space of gram negatives
enzymes, e.g. beta-lactamases - LPS
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lipopolysaccharide in outer membrane of gram negatives
composed of:
lipid A endotoxin
core polysaccharide
O-antigen (=polysaccharide) - lipid A
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endotoxin
highly toxic component of LPS in the outer membrane of gram negatives
conserved among gram negatives - 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 - 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 - name 3 optional structures of bacteria
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pilus
flagellum
capsule - flagellum
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motility - propeller
not a clear virulence factor
H antigen can be used for typing - H antigen
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antigenic determinant that makes up subunits of flagella
can be used in typing - 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-) - 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 - 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) - cytoplasmic changes in sporulation
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water loss
altered composition of DNA and proteins - vegetative cell can undergo either _____ or _____
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sporulation (nutrient deprivation) or
germination (nl envt) - how do you induce germination of a sporulating cell back to a normal vegetative cell?
- feed the organism