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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
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