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52 Cards in this Set
- Front
- Back
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What are five important roles of bacterial flagella?
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Motility
Adhesion Formation of biofilms Flagellar phase variation Mucosal inflammatory response |
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How can flagella help in motlity?
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To move and find their specific receptors so that the bacteria can bind and start to colonize the host
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How are flagella involved in adhesion?
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Flagella can be involved in adhesion to specific receptors
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How are flagella involved in biofilm formation?
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The bacteria turns off the expression of flagella to save energy when living in a biofilm
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What does flagellar phase variation allow?
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The bacteria can evade the adaptive immune response by switching flagellar antigenicities
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What are the two flagellar genes of Salmonella?
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FliC and FljB
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What do the early genes transcribed encode for? (In Salmonella flagella synthesis)
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The ring proteins that span the inner and outer membrane of Gram-negative bacteria such as Salmonella
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How are early transmembrane proteins transported?
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Through the classic Sec-pathway
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What happens once the early transmembrane proteins are transported from the cytosol to the periplasm, crossing the inner membrane?
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A signal peptide at the N terminus, of approximately 20aa is cleaved
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What are the late proteins produced in flagella production?
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The filament and hook
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How are the late proteins transported out of the cytoplasm?
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The late proteins travel from the cytoplasm to the outermembrane using the flagellar-specific export pathway
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How does the flagellar-specific export pathway work?
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The proteins travel through the channel formed by the rings and proteins of the early genes
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How many subunits is the flagelllum filament made of?
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30 000
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What drives the energy of rotation of the flagellum?
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The proton membrane gradient
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What forms the stator of the flagellar motor?
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The 8 units of MotA/MotB proteins
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Which proteins of the flagellum actually rotate?
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The FliG proteins
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What is the process of flagellar rotation?
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Protons travel through the 8 units of MotA/MotB and interact with the ring of approx 32 FliG proteins, driving the rotation of the FliG ring and causing rotation of the flagellum
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How many rotations does the flagellum undergo per second?
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250 rotations/sec
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How many protons are required to drive a single rotation?
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1000 protons/rotation
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What is the maximum speed of a bacteria?
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15-100 um/second
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What are the subunits of the Pseudomonas aeruginosa flagellum?
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FliC
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What is FliD?
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The flagellar cap protein of the flagella of Pseudomonas aeruginosa
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How does FliD assist Pseudomonas in colonizing the airway of CF patients?
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FliD binds to mucin (MUC-1), once bound, P aeruginosa can start to divide and colonize the lungs
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How do bacteria (P. aeruginosa) move once attached to a surface?
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Using Type IV pili
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How do bacteria move on the surface?
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They glide by extending and retracting the pilli
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What do the cells form before a biofilm?
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Microcolonies
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How do microcolonies differentiate into biofilms?
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Through quorum sensing
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What is the structure of biofilms and what are they composed of?
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Mushroom-like, 20-30% volume bacteria, the rest is mostly a matrix composed of polysaccharides and proteins and DNA from the environment
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What is FljA?
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A transcriptional repressor of FliC and is part of the same operon that encodes for FljB
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What is Hin recombinase?
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Mediates a crucial step in the Flagellar phase variation- it excises the fljB promoter every so often
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What happens once the fljB promoter is excised?
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Its orientation will be switched, rendering the promoter non-functional
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What is a consequence of the fljB promoter being non-functional?
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FljB and FljA will no longer be transcribed, and therefore FljA can no longer repress FliC, and therefore FliC will be flagellin subunit produced
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What is a consequence of FliC being produced instead of FljB?
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The flagella switches antigenicities, and thus the antibodies made against FljB will not work against FliC, and this is a way Salmonella can evade the host immune response
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Which Toll-like receptor recognizes flagellin?
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TLR5
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What is the difference between TLR5 recognition of Salmonella flagellin and H. pylori flagellin?
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The recognition of Salmonella flagellin triggers a robust immune response, while the recognition of H.pylori does not cause inflammation
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Why would Salmonella trigger a robust immune response?
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Because it wants to reach the underlying macrophages of the tissue to infect as many as possible- destroying the tissue in the process
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Why would H. pylori not trigger inflammation?
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It survives for a long time in the host
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What are some pathways that TLR5 ligand binding triggers?
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MAPK and NfKb signalling pathways
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What do TIRs interact with?
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MyD88 adaptor protein
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How many TLRs have been identified in mammals?
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11
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What do TLRs recognize?
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PAMPS (Pathogen associated molecular patterns)
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What does TLR9 recognize?
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CpG bacterial or viral DNA (unmethylated)
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What does TLR3 recognize?
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dsRNA
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What does TLR4 recognize?
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LPS on Gram negative bacteria
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What is Ipaf?
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Cytoplasmic receptor of flagellin
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Which family is Ipaf apart of?
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NOD-like receptors
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What does NOD stand for?
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Nucleotide-oligomerization Domain
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How is it possible for flagellin to interact with the intracellular Ipaf?
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The flagellin can either be secreted into the cell by Type III or IV secretion systems, or bacteria residing in the phagosome can inject the flagellum into the cytoplasm
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What happens when flagellin interacts with Ipaf?
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Ipaf changes conformation, allowing it to oligomerize
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What is CARD?
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A domain on Ipaf that once Ipaf oligomerizes, interacts with pro-caspase 1, cleaving it to form the active caspase-1
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What can activation of caspase-1 result in?
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Macrophage cell death by apoptosis or inflammation
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What do NOD1 and 2 recognize?
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They each recognize different parts of peptidoglycan and are cytoplasmic receptors
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