In this section, we aim to present all the composite parts that we have built and used thorough our project. In addition we introduce our best composite part: the pBAD-Gp2 construct, which provides a novel non-lethal way of inhibiting the growth of bacteria.
This year our best composite part is the pBAD-Gp2 construct, a new tool for repressing growth in bacteria without killing the host cell. We have demonstrated that the population is able to recover its initial growth rate once Gp2 is no longer expressed. We are excited to provide this new growth regulator for the synthetic biology community and for future iGEM teams.
In the presence of arabinose (the promoter was active from 100 μM L-arabinose), the araC transcriptional regulator activates the pBAD promoter, resulting in the production of Gp2, a protein from T7 phage. Gp2 binds reversibly to the bacterial RNA polymerase, preventing protein production, and preventing the cell from dividing (Bae, B. et al, 2013).
Figure 1. The pBAD-Gp2 construct.
The part was created by cloning a synthesised sequence block that contained Gp2, an RBS and the biobrick prefix and suffix, into an pBAD construct created by the 2014 Imperial iGEM team.
The construct effectively downregulates the growth of E. coli in response to arabinose, and does so in a reversible manner. We believe it is a good alternative to existing growth control methods, especially for controlling co-culture, for several reasons. You can read more about our characterisation data on our results page.
- Controlling cells in this way doesn’t require the usage of supplemented or minimal media, as in the case of antibiotics and auxotrophy.
- The system can easily be induced by L-arabinose, and switched off by D-glucose, both of which are non-toxic.
- Gp2 is particularly good for regulating population size in co-cultures, as it only affects the size of one population.
Bae, B., Davis, E., Brown, D., Campbell, E.A., Wigneshweraraj, S. and Darst, S.A., 2013. Phage T7 Gp2 inhibition of Escherichia coli RNA polymerase involves misappropriation of σ70 domain 1.1. Proceedings of the National Academy of Sciences, 110(49), pp.19772-19777.