Part:BBa_K101008

Biological Comparator Inducible by IPTG and aTc

Control systems are an integral component of almost all aspects of life. Whether it is in industrial, biological, or chemical applications, controllers provide a way to keep systems functioning properly. A vital part of any control system is the comparator. This component compares a set point value and a measured value, and determines which is larger. It then sends the appropriate signal to the controller, which reacts to bring the system back to the set point. In typical applications, the controller equipment is electronic. However, our team set out to create a comparator using only genetic components.

In order to undertake this task, a system involving six genes was designed. For our system, the two inputs (one representing the set point and one representing the measured value) are IPTG and ATC. These inputs will activate the transcription of the LacI and TetR proteins, and set in motion the rest of the system to produce the outputs. Depending on the amounts of the two inducer molecules added to the system, either green fluorescent protein (GFP) or red fluorescent protein(RFP) will be produced.

This device was designed for use in the DH5alphaPro E.coli, in which TetR and LacI are constitutively produced. The comparator is a composite of four smaller parts, each composed of a promoter, RBS, gene, and terminator. This constitutive production creates the baseline state of the device, in which neither of the reporter genes (RFP and GFP) are expressed. Addition of IPTG and/or aTc to the system inhibits the repression of LacI and TetR and allows reporter expression to occur.

Within the device are 4 individual composite parts. The first is the Lambda cI gene driven by the TetR promoter. This is followed by the p22 mnt protein which is driven by a LacI promoter. RFP expression is controlled by a TetR/p22 mnt dually repressed promoter, while GFP expression is controlled by a LacI/Lambda cI dually repressed promoter. Thus, when IPTG is present, only GFP should be expressed. Similarly, when aTc is present, only RFP should be expressed. It is this response that allows this device to function as a comparator.

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  INCOMPATIBLE WITH RFC[21]

  Illegal BglII site found at 2466
  
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  INCOMPATIBLE WITH RFC[1000]

  Illegal BsaI.rc site found at 2293