This year (2018) the iGEM Team TecMonterrey_GDL decided to contribute into the Interlab study measurements. The goal of the study is summarized in achieving a way to reduce lab-to-lab variability in fluorescence measurements via normalizing to absolute cell count or colony forming units. The approaches taken were indicated by the iGEM measurement team: 1. Converting between absorbance of cells to absorbance of a known concentration of microsphere silica beads 2. Counting colony-forming units (CFU) from the samples The team followed a series of protocols created to help standardize the measurement of GFP (green fluorescent protein), which is widely used as measurement marker. Specifications: The equipment we used was Cytation 3 by Biotek. It can measure both absorbance and fluorescence. And the pathlength correction was disabled. The temperature of the measurements was done at room temperature.

Calibration Protocol 1: OD600 Reference point - LUDOX Protocol

The first protocol’s goal was to obtain a conversion factor between absorbance measured and the OD600 measurement as it occurs in spectrophotometry measurements. This was made with the kit provided LUDOX CL-X (45% colloidal silica suspension) provided by iGEM and sterile mili Q water, reactants were added accordingly to the protocol and the obtained results are shown in the next table (Table 1):