Team:Cambridge/Project

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(Design)
(Our Solutions)
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*'''A Catalogue of Threshold Devices''': To avoid being limited to the sensitivity of the promoter and in order to be able to detect distinct concentrations of an inducer using just one promoter, we see the need for a catalogue of threshold devices.  These devices allow you to "tune" your biosensor, such that it reports meaningful concentrations of the inducer appropriate to the biosensor's application.   
*'''A Catalogue of Threshold Devices''': To avoid being limited to the sensitivity of the promoter and in order to be able to detect distinct concentrations of an inducer using just one promoter, we see the need for a catalogue of threshold devices.  These devices allow you to "tune" your biosensor, such that it reports meaningful concentrations of the inducer appropriate to the biosensor's application.   
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*'''Colour Output''': What if we could "see" the concentration of an inducer in a sample by a change in colour of the biosensor?  After all, we can "see" if a child has a fever using a thermometer strip and we can "see" the pH of a solution using a pH indicator; both device use colour as meaningful, simple output.
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*'''Colour Output''': What if we could "see" the concentration of an inducer in a sample by a change in colour of the biosensor?  After all, we can "see" if a child has a fever using a thermometer strip and we can "see" the pH of a solution using a pH indicator; both devices use colour as meaningful, simple output.
== Project Details==
== Project Details==

Revision as of 14:35, 3 September 2009


Project

Abstract

Improving Biosensors

The Parts Registry's repertoire of input-sensitive devices is incredibly varied. Teams have engineered E. coli to be sensitive to a wide range of environmentally significant compounds, including arsenic, mercury, lead, cyanide, etc., to genetically engineer biosensors as an alternative to other available technologies. The Cambridge 2009 iGEM team identified two stumbling blocks in biosensor design.

  • Sensitivity: By utilizing an input-sensitive promoter, the biosensor is limited by the sensitivity of the promoter. For example, the promoter might be sensitive to input concentrations which have no real world meaning. The promoter's sensitivity could be too low, so it reports concentrations below levels of real-world interest. Alternately, the promoter's sensitivity could be too high, so it reports concentrations above those which might be considered "dangerous" or environmentally significant.
  • Output: Previous iGEM biosensor projects have used pH, electrical conductance, and fluorescence as output. However, these reporter mechanisms require further steps to read the output.

Our Solutions

  • A Catalogue of Threshold Devices: To avoid being limited to the sensitivity of the promoter and in order to be able to detect distinct concentrations of an inducer using just one promoter, we see the need for a catalogue of threshold devices. These devices allow you to "tune" your biosensor, such that it reports meaningful concentrations of the inducer appropriate to the biosensor's application.
  • Colour Output: What if we could "see" the concentration of an inducer in a sample by a change in colour of the biosensor? After all, we can "see" if a child has a fever using a thermometer strip and we can "see" the pH of a solution using a pH indicator; both devices use colour as meaningful, simple output.

Project Details

Design

The Product

Our product reports the concentration of an inducer by colour:

Cambridge prototype3.jpg

Each well on the palette contains a different bacterial strain, which produces pigment only when the inducer is above a specific concentration. Thus, the top well turns brown at very high inducer concentrations, while the red well is the first to be activated by the very lowest concentrations of an inducer. The orange pigment in the bottom well is constitutively expressed to show that the bacteria are alive so the product is functional.

The Genetically Engineered Machine

Each bacterial strain is a machine built from a three part system:

Cambridge newGenericdevicE.jpg

  • Sensor: Our sensor system is sensitive to different concentrations of an inducer.
  • Threshold device: The threshold device is responsible for the sensitivity to the inducer, and acts as an "on" switch to activate pigment production once the inducer has reached a threshold.
  • Colour: Pigment production.

Components

The three part system can be described by the system diagram below:

Cambridge systemdiagram1.jpg

  • Sensor: Our project was output-focused, so we concentrated on the second two parts. For our proof of concept we used an arabinose sensitive promoter as the sensor. Future extensions of our project would include using our device with other input-sensitive promoters in the registry.
  • Threshold Device: This construct is based on Cambridge 2007's amplifiers.

Experiments

Results

(Preliminary): A few of the pigments we have available:

Cambridge 4colours.JPG

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