Difference between revisions of "Team:NUS Singapore-A/InterLab"

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   <p>In the first method, silica beads are used to estimate the actual amount of cells during fluorescence measurement. These beads are modelled after a typical E. coli cell, and are thus expected to scatter light in a similar way to E. Coli cells. As a sample of these silica beads give a consistent and known absorbance measurement at 600 nm, absorbance measurements from a sample’s cell density can be converted into an “equivalent concentration of beads” measurement that should be more universal and comparable between different labs.</p>
 
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   <p>In the second method, cell concentration is approximated is by plating a known volume of the sample and letting bacterial colonies grow. As each bacterial colony is assumed to represent a single cell (for cells that do not stick together), the cell concentration in the sample is then directly proportional to  the number of CFUs. Using a scaling factor computed from negative and positive control CFUs, a conversion factor from absorbance to CFU can be computed.</p>
 
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Revision as of 12:54, 17 June 2018

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Interlab Study

Objectives

A challenge of synthetic biology is repeating measurements in different laboratories. For example, fluorescence data is difficult to compare either because it is reported in different units, or because different groups handle raw data differently. iGEM’s Measurement Committee thus aims to use the InterLab Study to eventually develop absolute units for measurements of green fluorescent protein (GFP) in a plate reader. This will improve the measurement tools of synthetic biologists. This year, the Committee aims to discover if it is possible to reduce lab-to-lab variability in fluorescence measurements by normalizing to absolute cell count or colony-forming units (CFUs) instead of optical density (OD). For this, we were required to measure the cell density of Escherichia coli (E.Coli) DH5⍺ cells using the methods below.

Methods

In the first method, silica beads are used to estimate the actual amount of cells during fluorescence measurement. These beads are modelled after a typical E. coli cell, and are thus expected to scatter light in a similar way to E. Coli cells. As a sample of these silica beads give a consistent and known absorbance measurement at 600 nm, absorbance measurements from a sample’s cell density can be converted into an “equivalent concentration of beads” measurement that should be more universal and comparable between different labs.

In the second method, cell concentration is approximated is by plating a known volume of the sample and letting bacterial colonies grow. As each bacterial colony is assumed to represent a single cell (for cells that do not stick together), the cell concentration in the sample is then directly proportional to the number of CFUs. Using a scaling factor computed from negative and positive control CFUs, a conversion factor from absorbance to CFU can be computed.

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Results

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Discussion

Conclusion

★ ALERT!

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InterLab

Bronze Medal Criterion #4

Standard Tracks: Participate in the Interlab Measurement Study and/or obtain new, high quality experimental characterization data for an existing BioBrick Part or Device and enter this information on that part's Main Page in the Registry. The part that you are characterizing must NOT be from a 2018 part number range.

For teams participating in the InterLab study, all work must be shown on this page.