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Host/ParasiteRelatio

lecture 2 sperandio

Question	Answer
most common ways to penetrate the mucin layer	no receptors for mucin, degradative enzymes, being motile
common entry point for bacteria in the gut mucosa	M cells - have a thinner mucin layer
what bacteria use to adhere to host cells	pili & fimbriae (initial, more loosely) & afimbrial adhesins (usually most strongly, like E. coli AIDA)
definition of biofilm	polysaccharide slime; 3D structural pillars with interlaced bacteria and channels that bring in nutrients and allow toxins to diffuse out
examples of surfaces biofilms can develop on	body surfaces like teeth and lungs of CF pts, plastic implants like artificial valves or prostheses
compound released by bacteria to chelate iron in host (so they can take it back up to use it)	siderophores
host factors that bacteria bind to sequester iron	transferrin, lactoferrin and ferritin
Iron-abstinent bacteria use what element instead for enzymatic cofactors?	manganese
example of specie that rearranges host cytoskeleton to force it to eat them	Shigella
examples of bacteria that force phagocyte uptake then prevent phagosome-lysosome fusion	Salmonella spp. and Mycobacteria tuberculosis
example of bacterial genus shown in class that uses actin in host to propel itself through cytoplasm	Shigella
3 important features of pathogenicity islands	have different CG content than rest of chr, usually inserted close to tRNA genes, acquired through horizontal transfer
type III secretory system	essentially a molecular syringe inserted by bacterium into host cells to deposit virulence factors; spans both membranes
2 ways GP bacteria with capsules resist phagocyte-mediated killing	changing their capsules to resemble host polysaccharides or sialic acid
2 ways GN bacteria with LPS resist phagocyte-mediated killing	attach sialic acid to LPS O-antigen and change length of LPS O-antigen to make MAC form too far away from bacterium
___ bacteria can have both exotoxins and endotoxins.	only GN
The endotoxin of GN bacteria aka _____	LPS
Exotoxins are found in both GP and GN bacteria.
Bacterial toxins are encoded within _____.	bacteriophages and plasmids
type I toxins aka _______	superantigens
type II toxins aka _______	membrane-disrupting toxins
mechanism of superantigen toxicity	bind indiscriminately to MHC class II on macrophages and TCRs, cause overwhelming toxic shock when as many as 1:5 T cells are activated
example of type II toxin	Staphylococcus aureus alpha toxin
mechanism of type II toxins	form pore connecting host and bacterium, increased osmotic pressure shoots water into the host cell and ruptures it; also phospholipase rushes in and degrades polar head groups from CM
type III toxins aka _____	A-B toxins
mechanism of type III toxins	A-B toxins are held together by disulfide bond. one or more B subunits bind host cell receptor, toxin is endocytosed and A (activity) portion moves into cytoplasm
2 examples of A toxin activity within host cells	ADP-ribosylating various proteins or RNAse activity
2 diseases known to be caused by A toxins that ADP-ribosylate important proteins within host	diphtheria and cholera

Created by: sirprakes on 2011-08-30

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Host/ParasiteRelatio

lecture 2 sperandio