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A sensing array of radically coupled genetic ‘biopixels’
20.385April 25, 2012Sabina Sood
Arthur Prindle, Phillip Samayoa, Ivan Razinkov, Tal Danino, Lev S. Tsimring & Jeff Hasty
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Background
• Quorum sensing – used by bacteria to coordinate gene expression
• Biopixels – small oscillating bacterial colonies on the microfluidic chip
• Hydrogen peroxide – oxygen-oxygen single bond
• Redox signalling – when free radicals act as biological messengers
• Arsenite – compound poisonous to multicellular life
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Overview
Purpose: To construct a robust circuit in a noisy cellular environment
I. Construct microfluidic arrayII. Test sensing arrayIII. Engineer arsenic-sensing biosensorIV. Characterize arsenic biosensor
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Construct microfluidic arrayNetwork diagram
Quorum sensing:• luxI: produces AHL
• aiiA: degrades AHL
Redox signalling:• ndh: produces H2O2
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Construct microfluidic arrayDevice setup
http://www.nature.com/nature/journal/v481/n7379/extref/nature10722-s3.mov
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Test sensing array
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Engineer arsenic-sensing biosensorNetwork diagram
Thresholding:• luxR: produces
LuxR
• ArsR: inhibits luxR
Period modulation:• luxI: produces AHL
• ArsR: inhibits luxI
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Characterize arsenic biosensor
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Characterize arsenic biosensor
Thresholding: ON/OFFPeriod modulation
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Concerns
• Not a lot of points on the sensor calibration curve
• Arsenic sensor: “reliably quantify arsenite levels”
• Used 0.8 μM for sample period modulation sensor output
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Conclusions
• Combine two modes of communication:- Quorum sensing- Redox signalling
• Modify sensing array to detect arsenite:- Thresholding- Period modulation
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Significance
• Coordinate bacteria behavior over large length scales
• Foundation for low cost genetic biosensors
• Biosensor used for detecting heavy metals and pathogens
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Questions?