Part:BBa_K1045016:Experience
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Applications of BBa_K1045016
We used this part as a construction intermediate to obtain our DarR reporter system BBa_K1045017. Since this composite part was functional, we assume the construction intermediate BBa_K1045016 to be functional, as well. The characterization experiments for BBa_K1045017 are described below:
Microscope data
For characterization, E. coli BL21 was transformed either with BBa_K1045017 or with BBa_K1045013 as a control. Both strains were grown in the abscence of c-di-AMP and subjected to fluorescence microscopy.
In BBa_K1045013, gfp is placed downstream of a strong promoter and the DarR operator. This vector does not encode for DarR. The strong fluorescence of the cells transformed with BBa_K1045013 (Fig. 1 top) indicated that GFP was expressed. However, when transformed with BBa_K1045017 (Fig. 1 bottom), the cells showed almost no fluorescence. In contrast to BBa_K1045013, BBa_K1045017 encodes for DarR. The low fluorescence suggested that DarR was expressed and active as a repressor down-regulating gfp transcription. In conclusion, BBa_K1045017 was active, suggesting that BBa_K1045016, too, encodes for a functional darR gene.
Plate reader data
We furthermore produced quantitative data characterizing the growth and the fluorescence over time of the BL21 E. colis we transformed with the DarR reporter system construct BBa_K1045017. As a control, we used E. coli cells harboring the BBa_K1045013 plasmid. The following graphs show the results of the plate reader experiments performed to quantify the strength of the DarR construct in E. coli. Shown are growth curves measured at the wavelength 600 nm for the cell density (Fig. 2) and 509 nm for the GFP (Fig. 3), which is encoded in the construct. For each measurement, three technical and two biological replicates were done. The graphs show the mean value of the technical replicates and one of the biological replicates. As written in the legend, a dilution series of c-di-AMP was used to test the reaction of the DarR reporter system to the nucleotide. Experimental setup: total time 21 h; 15 min measurement interval; 37°C, medium shaking; 96-well titer plate; Synergy Mx Monochromator-Based Multi-Mode Microplate Reader; Gen5 V2.01
As in the microscope experiments described above, the expression of the reporter was prevented (even without c-di-AMP), when DarR was encoded in the vector. Though the DarR reporter system BBa_K1045017 could not be regulated by c-di-AMP, the expression units seem to have been operative. This suggests, as well, that part BBa_K1045016 harbors a functional darR gene.
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