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Team:UANL Mty-Mexico/Wetlab
From 2013.igem.org
Wetlab
We divided our circuit in sub-circuits, or modules. Each module comprises a single function of our system. These modules are:
- The mCherry switch.- this switch comprises the 37°C thermometer and an mCherry reporter right downstream from it.
- The GFP switch.- this switch is similar to the mCherry one, but has a 32°C thermometer and a GFP reporter.
- The LacI-GFP switch.- in this switch, a 37°C thermometer is regulating the expression of a LacI gene, which in turn is regulating the expression of a GFP reporter. This GFP reporter is also under the regulation of a 32°C thermometer. In this way, we expect to see two different states: OFF at temperatures below 32°C; ON when temperature is between 32°C and 37°C; and OFF again when temperature is above 37°C.
- The TetR-mCherry switch.- here, an mCherry reporter is regulated by a 37°C thermometer and a pTet promoter; this switch also includes a TetR construction.
- The cI-TetR-mCherry switch.- this switch is similar to the previous one, but also includes a cassette that expresses a thermolabile version of cI. In this way, the expression of mCherry will be ON only at temperatures between 37°C and 42°C and OFF at other temperatures.
Fluorescence Assay
The part BBa_K110006 which has mCherry under the regulation of the TetR and the RNA Thermometer specific for the 37°C. To verify the operation, a series of experiments were developed in which the bacteria with this part were exposed to different temperatures under the following protocol.
1.- The synthetic constructions were transformed in DH5-alpha and planted in Petri dishes with LB Agar and the corresponding antibiotic.
2.- Twenty different clones were chosen and planted in test tubes with 3 mL and LB medium. They were incubated at 37°C to overnight until saturation.
3.- A visual section of the clones with more and less expression of the Red Fluorescent Protein (mCherry ) was made.
4. 20 μL of the cultivation of all the night were transferred to eppendorf tubes in the microcentrifuge with 500 μL of LB medium and antibiotic. A tiny hole was made to the cap of these tubes with a needle to allow the oxygenation of the cultivation over the experiment.
5.- They were placed at the thermomixer, in eppendorf adjusting the temperature to 25, 37 and 42°C and shaken at seventeen hours at 900 rpm.
6. 200 μl were took from each cultivation and placed in a black 96 well plaque Costar to make measurements in a fluorometer Biotech Synergy HT with the following conditions for mCherry. Excitation filter of 530 +/- 25nm, emission filter of 590 +/- 35 nm, sensibility of 85.
7. The optical density was determined for each cultivation to normalize the measurements reading in a Petri dish with transparent 96 well plaques Costar, with a wave length of 630 nm.
8. The data was processed with Excel.
Figure 1. Fluorescence assay for mCherry synthetic construction. The image represent the protocol that we follow to measure the relative fluorescence. We growth the different clone in 25, 30, 37 and 42oC and measure the Fluorescence and OD to normalise the results.
