Part:BBa_K3777017

CtcS-T7(ctcO)-3WJdB

Basic biosensor device for Chlortetracycline detection.

Usage and Biology
The genetic circuit was composed of a coding sequence of Chlortetracycline repressor which was inserted into an expression vectors with a consitive promoter(BBa_J23114) and RBS(BBa_K3777030), as well as 3WJdB(BBa_K3777000) under the control of T7 promoter (BBa_K3777006). The terminator we used were BBa_B0010 and BBa_M36305.(Fig 1)
When CTE was absent, TetR would bind to the inducible promoter（PI）and prevent RNA polymerase from initiating transcription, thus repressing the expression of reporter gene. If tet was present, TetR would no longer able to bind to the promoter, resulting in the expression of reporter gene.
We expressed this circuit in the E. coli BL21(DE3) cells for tetracycline detection. Thus we could roughly deduce the concentration of the antibiotics in the sample according to the fluorescence intensity.
Fig.1 Schematic overview of the genetic circuit.
Results
To verify the functionality of the biosensor, we performed a plate-reader experiment and measured optical density and fluorescence intensity every hour. We observed a correlation between concentration of antibiotics in the sample and intensity of fluorescent signal.
The figure shows that our cuircuit can recognize different concentrations of Chlortetracycline, and the fluorescence value was positively correlated with Chlortetracycline concentration which proves that our part can Detect the concentration of Chlortetracycline，and our reporter gene 3WJDB is surprisingly sensitive.

Reference：Alam Khalid K,Tawiah Kwaku D,Lichte Matthew F,Porciani David,Burke Donald H. A Fluorescent Split Aptamer for Visualizing RNA-RNA Assembly In Vivo.[J]. ACS synthetic biology,2017,6(9)

Sequence and Features

Assembly Compatibility:

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

  Illegal NheI site found at 7
  Illegal NheI site found at 30
  Illegal NheI site found at 911
  Illegal NotI site found at 579
  
• 21
  INCOMPATIBLE WITH RFC[21]

  Illegal XhoI site found at 588
  
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  INCOMPATIBLE WITH RFC[1000]

  Illegal BsaI site found at 323