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Revision as of 03:32, 17 July 2018
Introduction: What is InterLab
Reliable and repeatable measurement is key to synthetic biology. It is essential for a standard protocol to be established so that the same measurements can be repeated in different labs.
This year’s interlab study is aimed to reduce the variability of cell count measurements by replacing OD600 measurement which varies between labs with directly counting of colony forming units (CFU) to determine the number of cells in each sample. Then the mean GFP expression level by each cell can be determined by dividing the already standardized GFP expression level of the sample by the number of cells in that sample.
This is the 5th year of InterLab and we have the following question:
Can we reduce lab-to-lab variability in fluorescence measurements by normalizing to absolute cell count or colony-forming units (CFUs) instead of OD?
Materials
DNA/Plasmids
- Negative Control: BBa_R0040
- Positive Control: BBa_I20270
- Test Device 1: BBa_J364000
- Test Device 2: BBa_J364001
- Test Device 3: BBa_J364002
- Test Device 4: BBa_J364007
- Test Device 5: BBa_J364008
- Test Device 6: BBa_J364009
Apparatus
- 96 well plates (provided by Peking University)
- Plate reader
- Foil covered 50 ml tube
- Eppendorf tubes
- Pipettes
Materials
- LUDOX CL-X
- Silica beads
- Fluorescein
- Phosphate buffered saline
- LB media
- Chloramphenicol
- LB plates
- distilled water
Protocols
We followed the protocol provided by iGEM HQ so that inter-laboratory errors can be reduced. Protocols we used can be found here:
2018 InterLab Plate Reader ProtocolHelp: Protocols/Transformation
During the first day, we resuspended DNA from distribution kit (Kit Open Day!) and transformed the plasmids into Escherichia coli DH5α competent cells.
For the second day, firstly we picked single colonies from transformation plates and prepared overnight cultures; we also finished particle and fluorescence calibration.
The third day was fairly occupied.
- Overnight cultures were collected for assays. Essentially, each culture was diluted into same starting Abs readings and incubated for 6 hours. Samples were taken at the starting time and after 6 hours. Abs and fluorescence readings were measured for each sample and then imported into excel file.
- While we were waiting for incubation, we diluted the starting sample culture for Colony Forming Units protocols and spread 36 LB plates.
- We nearly forgot to calibrate OD reference points at the end of the day!
At last, we counted the colonies (colony forming units) in those 36 plates. It was just an exhausting process!
Results
The results are shown in the tables and figures.
Calibrations
OD600 reference point:
Table 1. OD600 Reference Point.
Figure 1. Particle Standard Curve.
Figure 2. Fluorescein Standard Curve.
Raw Plate Reader Measurements
Fluorescence Raw
Table 2. Raw Plate Reader Measurements of Fluorescence Raw at 0 hour.
Table 3. Raw Plate Reader Measurements of Fluorescence Raw at 6 hours.
Abs600 Raw
Table 4. Raw Plate Reader Measurements of Abs600 Raw at 0 hour.
Table 5. Raw Plate Reader Measurements of Abs600 Raw at 6 hours.
Evaluation
Thanks to Molecular Biology Laboratory in Tsinghua University, we could follow the protocols without issues regarding apparatus and reagents. Also, we’d like to appreciate our advisor and anyone who helped us in Tsinghua and Peking University for providing suggestions and guidance during InterLab studies.