MMI 302 Lecture: Ruby 1

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  1. Quorum Signaling is an example of
    • bacterial cell to cell signaling
    • Allows determination of how many bacteria are in vicinity
  2. Quorum
    Minimum number of things needed to take an action
  3. What does Quorum signaling control?
    Specific gene activation
  4. AHL
    • acyl-homoserine lactone
    • Common molecule for quorum signaling in proteobacteria
    • Made by AHL synthase
    • Binds protein receptors to activate gene
  5. Signal levels based on density of bacteria
    • Low levels, signals diffuse away
    • High levels, no net diffusion, bacteria know that they have friends around
  6. Biofilm Development
    • Free living bacteria (i.e. planktonic bacteria) begin attaching to surface
    • More bacteria grow and attach in response to Quorum signalling
    • Form extracellular polysaccharide membrane
    • Become pillar shape
    • When nutrients run out the film degrades and cells re-disperse
  7. Experimental evidence for quorum signalling in virulence
    Wild-type and non-QS mutant are inoculated into a mouse. Far less death in non-QS mutant.
  8. AHL/Peptide QS Molecules
    • AHL: 5 member 1 O ring with subs, Gram -
    • Peptide: Used by Gram +
  9. Peptide QS
    Peptide signalers are produced, accumulate, activates cascade for gene transcription
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MMI 302 Lecture: Ruby 1
2013-11-04 17:03:25
MMI 302

MMI 302
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