Part:BBa_K2629003:Experience

Experiments were done on a plasmid in which the probe has been inserted, thanks the Gibson technic, in psB1C3-BBa_J04450.

Results of the clonning of the BFP gene instead of BBa_J04450 and the probe clonning

This is the alignments realized:

- between psB1C3-BBa_K2629003 and new BFP gene (A).
- between psB1C3-BBa_K2629003 and the probe after probe activation by PCR linearization (B).

Unfortunately, this is not the result that we expected. In fact, the sequencing shows that the cloning of the probe did not work. Regrettably, we did not have the time to make more sensibility tests. However, the substitution of RFP gene by BFP gene did work well as we can see one the figure A. This means that a new biobrick was constructed with the same RBS, promoter and terminator system as BBa_J04450 but with another gene than mRFP E1010 --> K592100 (BFP gene).

Test A: Is this part able to detect the target for which it has been designed ?

Unfortunately, results were too heterogenous to bring any conclusions. Indeed, the number of colonies, for the 1:100 and 1:200 ratios, expected was not good enought (there is a possibility that the detector was badly digested and was consequently badly transformed).

Test B: Is this part able to detect specifically the target for which it has been designed ?

Another limitation driven by the kit is the purity of the sample. Indeed, the detection occurs when the target is mixed with a lot of foreign and unknown DNAs. To estimate specificity, i.e. the ability of the detector to identify the true positive, the detector has to be tested with “false target sequences”, more or less homologous to the original targets. To do so, an algorithm was made by iGEM Grenoble 2017 to give random sequences with 5%, 15%, 25% and 50% randomly modified pairs of nucleotides (length is kept at 42bp). In addition, the probe detects a DNA fragment with mutations causing resistance. As a result, three other controls have been added:
- One without the 2 mutations
- One with the first mutation
- One with the second mutation

The algorithm can be found here :

Unfortunately, we did not have the opportunity and the time to carry out these experiments.

Conclusion

In conclusion, this probe aims to characterize a resistance marker of Pseudomonas aeruginosa. If the constructed probe recognizes the target, it hybridizes, the plasmid is circular and ready to be transformed. After this transformation in TOP10, the bacteria expresses the reporter gene which is blue in this case. The idea of ​​our project is to associate a color with a probe. The red color (RFP) for the probe characterizing the lysis of Pseudomonas aeruginosa and the blue color for the probe characterizing a resistance marker of Pseudomonas aeruginosa.

Finally, the probe was not inserted in this case. On the other hand, the substitution of the gene of the RFP by the gene of the BFP was a success. Unfortunately we did not have time to properly characterize this new biobrick. However, it could be used in several applications. As we have tried, it can be used in diagnosis with a report color.

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