Part:BBa_K1960002
Toggle switch controlled by sensing device
This part is a toggle switch controlled by sensing device such as quorum sensing systems. The promoter BBa_R0011 will be partly regulated when the device works, and then the expression of cI, BBa_C0051 will be limited, then the promoter BBa_R0051 will be regulated. After a long time, the expression of cI, BBa_C0051 will be drastically stopped, the device controlled promoter BBa_R0051, such as BBa_K1960001, a reporting device, will work.
In this schematic diagram (Figure 2), the sensor part is able to sense the signaling molecules.Then the responder expresses. The toggle switch is used to control the product of the lysis gene can make the engineered bacteria cracked. When the switch is in the "ON" state, the expression of the lysis gene is repressed. When the switch is in the "OFF" state, the inhibition of the lysis gene is counteracted. According to our circuit model, we chose the Gram-negative bacteria's quorum Lux sensing system as our sensor part. The toggle switch is consisted of lacI gene and cI gene.
Figure. The diagram of the mechanism that how the switch consisting of the cI gene and lacI gene works.
Usage and Biology
This part can be used as a delaying switch with a suitable signal controller, such as quorum sensing systems. To see how this part works, you can see BBa_K1960000.
When AHL around the engineered bacteria is at low concentration, AHL can't be sensed by the Lux sensor part, and the cI gene expresses at the wild-type levels, while lacI-2 and GFP are repressed since the cI protein is high. When AHL around the engineered bacteria reach a certain concentration, it can be sensed by the sensor part so the promoter Lux-pR will be activated, CFP and lacI-1 can also express. Then the CFP can be measured by fluorescence measurement, and the lacI-1's product-LacR protein can inhibit the expression of cI gene. As a result, lacI-2 and GFP can express. The LacI-2's product can further repress cI's expression, then GFP can be measured by fluorescene detection. The time interval of firstly detecting CFP's fluorescence and firstly detecting GFP's fluorescence can represent the delay time which the switch give for responder's expression.
Figure. The mean green fluorescence intensity in E.coli and its variety with time on the AHL of 1ng/μL, 10ng/μL, 20ng/μL and 0ng/μL.
The concentration of AHL didn't influence the expression of GFP directly. The GFP in 10ng/μL and 20ng/μL group started to express in the 420th minute and it had no significant difference in expression level. The GFP didn't express in 1ng/μL group.
Sequence and Features
- 10COMPATIBLE WITH RFC[10]
- 12COMPATIBLE WITH RFC[12]
- 21COMPATIBLE WITH RFC[21]
- 23COMPATIBLE WITH RFC[23]
- 25COMPATIBLE WITH RFC[25]
- 1000COMPATIBLE WITH RFC[1000]
| None |