Team:NUS Singapore-A/shadow/Composite Part

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OVERVIEW

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LIST OF COMPOSITE PARTS

Device Part Number Usage
PhtpG1-mRFP BBa_K2819118 Stress reporter
NANDA FILL ME BBa_I20270 Promoter MeasKit (J23151)


PhtpG1-mRFP

This part contains the coding sequence of mRFP put under control of the stress promoter PhtpG1. The promoter, PhtpG1, was carefully chosen because of sensitivity to synthetic construct-induced burden in E. coli. This distinct characteristic is especially valuable to our system because we were interested in quantifying real-time levels of stress generated by the expression of externally introduced constructs.

In our experiments, we were interested in the depletion of finite cellular resources during the expression of synthetic constructs constitutes an unwanted burden, which we define as cell stress,


hampering the growth and expected the performance of engineered cells in an unpredictable manner. Stress regulation has been shown to enable cells to outperform their unregulated counterparts in terms of protein yield, a remarkable discovery which we believe will have significant implications in the biomanufacturing field.

By quantifying cell stress via fluorescence, recombinant protein production can be optimized by the user simply by reducing cell stress i.e. switching off protein production (in our case, this can be done by turning on blue light).

Additionally, according to Ceroni et al. (2018), PhtpG1 displayed the best on/off characteristic out of the 4 promoters that were being investigated (htpG1, htpG2, groSL, and ibpAB). This feature allows the stress-reporting module, PhtpG1-mRFP, to not only respond rapidly, but also to maintain its receptivity in a dynamic cell microenvironment.



EXPERIMENTS

Abs600

  • Wavelength: 600nm
  • Read Speed: Normal
  • Delay: 100 msec

Fluorescence

  • Excitation: 485
  • Emission: 525
  • Optics: Top
  • Gain: 50
  • Light Source: Xenon Flash
  • Lamp Energy: High
  • Read Speed: Normal
  • Delay: 100 msec
  • Read Height: 7 mm

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CONCLUSION


The results from our experiment seem to indicate that normalizing fluorescence measurements to absolute cell count using the Study’s two methods will not be able to reduce lab-to-lab variability because counting colony-forming units do not return the expected cell concentration, i.e. the cell concentration modeled by the silica beads in Method 1. While both methods cannot be used independently to establish a robust fluorescence measurement system, it may be possible that lab-to-lab variability can be reduced if a different method of normalizing to absolute cell count is devised, replacing Method 1, Method 2, or both.