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Team:Edinburgh/Project/Future
From 2010.igem.org
Future Work: Sequential addition
One of the future expansions of the BRIDGE protocol that we have discussed involves using it to directly introduce genes in the genome next to each other without using the BioBrick method before-hand. For example, if you wanted to insert four genes with the steps described in the protocol section, it would take eight steps. If you do this with the method shown in Figure 1 below, it would only take four steps.
Figure 1: Using BRIDGE to directly insert genes into the genome.
At the first step of the process, the first antibiotic resistance gene and sacB are introduced alongside the first gene. The antibiotic resistance gene can then be replaced with the next gene and a second antibiotic resistance gene, thereby cycling the antibiotic resistance such that selection is different at each step. At the last step, both markers are removed and the final constructs can be selected for by growth on sucrose (growth on sucrose can also be used as a negative control at each stage, although this would only be to confirm the persistence of the marker).
The final construct would look as shown in Figure 2.
Figure 2: The theoretical final construct after using BRIDGE to directly insert genes into the genome.
The steps above are purely theoretical and have not yet been tested, but the principle behind them is not too distant from the original method, so it would be nice to attempt it if anyone ever gets the chance.
Future Work: A working protocol
So far we have been unable to produce cat/sacB recombinants using the protocol we have written up on this wiki. We believe we know where the problems lie.
We initially suspected that the plasmid containing the recombinase genes was incorrect, however a restriction digest of this with EcoRI gave the bands expected for that plasmid (see lab notes).
We thought perhaps cat was not very chloramphenicol resistant but we have demonstrated it's growth on cml40 and the titre indicated no chloramphenicol resistance at all in our transformants (see BRIDGE protocol and characterisation).
We eventually discovered notes on the protocol indicating that JM109 and DH5alpha are not suitable hosts for lambda recombination. Knowing this we have switched strain to K12. We are also using kanamycin resistance instead of chloramphenicol resistance.
If these experiments still don't work then the induction step needs to be change. For example, L-arabinose is essential but it might be needed in higher concentrations.
Future Applications
We want it to take over the world! ... fine, we'll settle for an RFC.
The advantages of the BRIDGE protocol over more traditional methods of BioBrick insertion have been documented here.
