From OpenWetWare
Jump to navigationJump to search

Project Wiki Home

Example 1: Use of toggle switch to make a genetic JK Latch

  • Paper: Biological Signal Processing with a Genetic Toggle Switch Patrick Hillenbrand , Georg Fritz, Ulrich Gerland 2018
  • Combinational logic is widely used in biological systems to integrate signals to have a regulatory effect on a gene.
  • The signal processing capability of any combinatorial logic is limited as output always depends on the current continuous output.
  • Sequential logic- output is dependent on memory/history.
  • Genetic toggle switch consists of two mutually repressing genes- it serves as the basis for simple sequential logic.

e.g. JK Latch


Core memory unit: genetic toggle switch

  • Sequential Logic in digital electronics is predominantly synchronous- ie it has a central clock that orchestrates the timing of all operations.
  • Biological systems must use asynchronous logic resulting in design constraints.

Example 2

  • Paper: A Glucose-Sensing Toggle Switch for Autonomous, High Productivity Genetic Control Bothfeld, W., Kapov, G. & Tyo, K.E.J., 2017.
  • Currently, many bioproduction strategies rely on growth-coupled production, because constitutive expression of the product pathway is more feasible than inducing production after growth
  • A decoupled growth and production phase strategy is needed for efficient economical bioproduction of chemicals.
  • A toggle switch has been developed that uses glucose sensing to enable this two-phase strategy.


Idealized strategies for biosynthesis of chemicals using cell factories. (a) Common biomass (solid line) and product (dashed line) profiles expected from a variety of biosynthesis strategies (green: decoupled growth and production, yellow: constitutive growth and production, red: constitutive pathway overexpression). (b) The integration of glucose sensing into the toggle switch architecture.

A functional genetic toggle switch

  • Unlike simple induction, a genetic toggle switch could enable complete activation to a new stable state that would eliminate graded induction.
  • The culture could stay in the production state even after the activating condition is gone due to the memory capacity encoded by the switch
  • The “new” switch state could be maintained stably during the entire production phase

Selecting Glucose Responsive Promoters

  • There was need to identify promotors with strong activation due to glucose depletion.
  • CRP(cAMP receptor protein) Promotors.
  • Different Glucose-Responsive Promoters Have Differing Activation Characteristics
  • A promoter with both a tight OFF-state and an ON-state with adequate expression during glucose-starvation is desirable

(Relevant to our project)

Advantages this has:

  • IPTG is expensive

Application of this

An IGem Project uses this for PHP Production.