Synthetic Biology - Devices - Recombination Switch
From Keaslingwiki
Goal
This project aims to create an invertible AND gate capable of remembering temporal information. Used as a composable biological part, such a switch would provide a useful means of encoding and retrieving information from a biological system.
Background
There are several inversion recombination switches found in prokaryotes, for example the Fim inversion recombination system of E. coli, and the hin system of Salmonella. They share a few common characterizations, such as unique inverted repeat sequence, and an invertase that recognizes the specific sequence.
The invertases bind to the inverted repeat recognition sequences, form a DNA loop, then cleave and ligate the looped DNA, resulting in the inversion of the DNA fragment inbetween the inverted repeats. Both the fim and the hin system have a gene flanking the inversion region, which is controlled by a promoter that reside within the region. The expression of the gene is dependent on the orientation of the promoter.
Bacterial inversion recombination system provides several advantages for use as a generic, composable switch:
- They are reversible.
- They are specific to the invertase and its recognition sequence.
- They are easy to refactor. The sequence elements required for inversion are known, and are flexible in what can be included within the inversion sites.
The Heritable Memory Switch
By using two inversion recombinations switches, we can construct a system that can respond to two separate inputs. By intercollating the sequences, we can construct a system that is affected by the previous input, and the system can "remember" what input it has seen before. (picture) Output of such system would look like the following:
| Input | Output |
|---|---|
| signal A | -- |
| signal B | -- |
| signal A, then signal B | Output 1 |
| signal B, then signal A | Output 2 |
