Team:Technion/Project/Overview
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Contents |
The general idea
Figure 1 presents the basic strategy for our three inputs AND gate. Each one of the inducers can be an environmental signal, to which the phage will respond. In the presence of all the inputs, the phage will be capable to resume its lytic cycle. The assembly of the lytic phage, is our circuit's output.
The inducers, promoters and bacterial strain
When considering the choice of our system's components, the choice of the inducers, promoters and bacterial strain is intertwined. We needed to minimize the number of plasmids used, therefore, the bacterial strain should provide us with as many regulatory overexpressed components as possible. Roee had the strain DH5αZ1, which expresses high levels of Lac and Tet repressor (LacR, TetR) as well as of AraC {1}. This allowed us to use the PTetO and the PLac/Ara promoters without the introduction of additional regulatory elements on plasmids. Consequentially, the inducers used were anhydrotetracycline (aTc) for PTetO and IPTG with arabinose for PLac/Ara.
The choice of the third promoter could no longer rely on host strain expression of required regulatory elements. Therefore, we chose the quorum sensing system based on the PLux promoter, which is induced by [http://partsregistry.org/3OC6HSL 3OC6HSL] (also known as N-(β-ketocaproyl)-L-Homoserine lactone). This made it obligatory for us to express the LuxR gene from a plasmid. Moreover, since the PLux promoter is leaky, we chose to introduce another regulatory element to reduce the basal level. This element is the theophylline induced riboswitch, which controls the level of translation of a given protein. More about these elements can be found in the YES gate #3 section.
The fluorescent proteins
The RNA polymerases and promoters
The phage
References
1. Lutz R., Bujard H. 1997. Independent and tight regulation of transcriptional units in Escherichia coli via the LacR/O, the TetR/O and AraC/I1-I2 regulatory elements. Nucleic Acids Research 25(6): 1203-1210.