Synthetic biology and all the engineering disciplines need to be reliable and repeatable, this year iGEM TecCEM 2018 is one of the teams that participated in the Fifth International InterLaboratory Measurement Study. In this page, we report the results obtained during all protocols.

Competent cell - transformation DH5-alpha

Transformations of all devices were performed, and the resulting transformant strains were plated on LB agar, with 35 μg/mL chloramphenicol. Two colonies per plate were separated into two independent cultures.

Verification

We verified the presence and size of the device plasmids in the transformant strains by running an agarose gel electrophoresis.

Table 1. Devices from the Interlab Study with their pait number and respective size.

Calibration Protocol

The main objective of this calibration LUDOX protocol is to use LUDOX CL-X to get the conversion factor between absorbance (Abs600) from the plate reader and the OD600 measurement.

Table 2. OD600 Reference Point - LUDOX Protocol

Particle standard curve - Microsphere Protocol

The aim of this protocol is to establish a standard curve from a microsphere solution. These microspheres have similar size and optic properties to bacterial cells, therefore, they may be used to calibrate. After preparing the Microsphere Stock Solution, serial dilutions were made in a 96-well plate as instructed. To achieve reliable results, the plate reader was set to shake the samples just before reading them. The reads were registered in the given Excel file and are shown below.

Fluorescence standard curve - Fluorescein Protocol

Following the protocol for the fluorescence standard curve using fluorescein, we prepared the corresponding reactants and the requested serial solutions in the 96-well plate.

Cell measurement Protocol

Table 3. Absorbance and fluorescence at hour 0 and hour 6.

After performing all three calibration measurements, we proceeded to execute the cell measurement protocol, previously having the overnight cell culture of each device and control. We use the same plate and volume that we used in the calibration protocol, also the same settings in order to make valid the measurement. We defined the difference between the measurement of the absorbance and fluorescence, starting in the hour 0 until the hour 6.

Colony Forming Units per 0.1 OD600 E. coli cultures

To preparing the starting samples we diluted overnight cultures of both positive and negative controls to the linear detection range of the plate reader. A duplicate of each culture was placed on the 96-well plate, as well as a blank. After measuring absorbance, cultures were diluted further to reach an OD600=0.1. A triplicate of each dilution was placed as instructed. The absorbance measurements were confirmed and used to prepare the respective dilutions for 12 starting samples at 0.1, six for each control. We diluted the cultures to a final OD600 of 0.1 and performed serial dilutions by transferring 100 μL to the next tube. The dilutions 3, 4, and 5 were used to spread 100 μL in LB+Cam plates. After an overnight incubation, we counted the colonies in each of the plates, being many of them uncountable. The counted colonies are shown below.

Table 4. Colony count