Lecture 7 Flashcards
Quorum Sensing
Minimum amount of molecules that must be present in order for microbes to do something
-this is how bacteria can communicate with neighbors
Lux
Prototypical quorum sensing system
-light
Luciferase
an enzyme that emits light
Is Allivibrio fischeri gram(-) or gram (+) bacteria
Gram (-)
Autoinducer molecules (AHL)
-can diffuse across cell envelope
-reaches high concentration inside cell if many cells are nearby
-binds to LuxR
Lux operon
regulates biominulescence
What produce autoinducer molecules
LuxI
What do autoinducers bind to and what happens?
LuxR
-LuxR dimerizes and binds to promoter to start transcription
True or false: LuxR can transcribe all genes in lux operon without dimerizing
False
-LuxR needs to be a dimer to transcribe all genes
Which 2 units make luciferase?
LuxA and LuxB
True or false: Only a few genes in the lux operon need to be transcribed in order to make light
False
-ALL genes need to be transcribed to make light
What does LuxI do?
produces autoinducers
What does LuxR do?
encodes autoinducer-transcription factor
Explain the steps of the Lux operon
- LuxI makes autoinducers
- Autoinducers diffuses into medium and accumulates
- AI reaches a concentration threshold and diffuses back into the cell–>activates LuxR–>activates lux transcription genes–>makes light (luiferase)
What is the quorum sensing signal in Gram (+) bacteria?
AIP-1
-small cyclic peptide
What is the quorum sensing signal in Gram (-) bacteria?
3OC6-HSL
