Team:Michigan/InterLab
InterLab Study
We participated in the iGEM Interlab study, following the 2018 Interlab Study protocol. Previous Interlab Studies examined variability in GFP measurements between labs. However, measurements of mean GFP expression per cell also depend on the variability between labs in measuring the cell count. We hope our work contributed making measurements of cell counts more reproducible. We first calibrated our plate reader to make absorbance values that approximate OD600 measurements with a spectrophotometer. We then made tenfold dilutions of a known concentration of microspheres and fluorescein to make particle and fluorescence standard curves. Once we had these standard curves, we transformed Dh5ɑ cells with one of 8 iGEM plasmids. Two colonies transformed with each plasmid were diluted to 0.02 Abs600, and both absorbance and fluorescence readings were taken for a 0 hour and 6 hour time point. To assess the correlation between OD600 and the number of cells in solution, we examined the number of colony forming units (CFU) for 2 positive control and 2 negative control cultures diluted to OD600 of 0.1. Once the cultures were diluted to OD600, serial dilutions were made and bacteria were plated at dilution factors of 8 x 104, 8 x 105, and 8 x 106.
We found the Interlab protocol very clear and accessible. We had slight difficulty obtaining the plate reader, but once we were allowed to use the plate reader of a lab on campus, the instructions in the protocol were straightforward to follow. We appreciated that the protocol and the Interlab Study explained how the measurements we were making contributed to the goal of the study as a whole.