Part:BBa_J04450:Experience

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Our aim was to evaluate RFP expression quantity of E. coli. In order to obtain this information, we agreed that the measurement of fluorescence intensity in certain OD values is the best approach. However, fluorescence quenching was a setback which we must overcome for accurate and reliable results. Because, as a result of quenching, fluorescence intensity counts do not give the actual amount of fluorescence expected from a certain OD value. Therefore we employed a curve fitting method suggested by Zhang et. al (2010) which is claimed to take the quenching problem into consideration

Where If is the fluorescence intensity; OD is the cell density; y0 is the offset; A1 is the amplitude; and t1 is the decay constant.
We chose BBa_J04450 for this experiment. And our negative control was again BBa_B0034.
There were nine bacterial concentrations prepared for one to five hours of IPTG induction. (All concentrations were prepared as triplicates.) Then a complete graph of all the induction durations was plotted with the help of the function shown above:

(■) 1 h induced; (●) 2 h induced; (▲) 3 h induced; (▼) 4 h induced; (♦) 5 h induced

As seen in the graph, fluorescence behaves exactly as expected and does not increase linearly with the increased bacterial concentration. However, IPTG induction effect is clear on fluorescence intensity. (Error bars were too small to be visible.)

Finally, the variables A1 and t1 of the fittings of each induction duration were used to obtain a mean fluorescence intensity (MFI) value:

By conducting this experiment, we were able to characterize RFP expression pattern of the part BBa_J04450 in the host Top Ten. Theoretical mean fluorescence intensity reflects the fluorescence quantum efficiency of the fluorophore RFP, and was found to be unrelated to the cell concentration. Since it is obvious from the results we have obtained that change in the OD does not correlate linearly with the change in the fluorescence intensity. Therefore this model proposes a solution to the unpredictability of the fluorescence amount coming from a certain bacterial population.

The characterization was performed by METU-TURKEY 2010 IGEM TEAM.

User Reviews

UNIQc5d2e91d33d4d95a-partinfo-00000006-QINU

••••• Antiquity

This review comes from the old result system and indicates that this part worked in some test.

••••• Marc.mtk

We've used this part as an alternative to the suicide part p1010 (ccdB) for selecting against cells that have been transformed with a [http://ginkgobioworks.com/support/BioBrick_Assembly_Manual.pdf destination plasmid]. It worked perfectly, and if i might say, it looks smashingly in LB medium ;).

UNIQc5d2e91d33d4d95a-partinfo-00000009-QINU