Team:Caltech/Project

Background and Motivation

One of synthetic biology's chief promises is the potential to construct artificial, self-regulatory genetic circuits. While intracellular genetic regulation, as exemplified by such model systems as the repressilator, is fairly well documented and explored, intercellular regulation, mediated by cell-to-cell signaling, remains less well characterized and explored. This year, the Caltech 2014 iGEM team focused on the implementation of non-endogenous bacterial quorum-sensing systems in E. coli, in hopes that successful transfer of these systems into E. coli will promote enhanced prototyping of intercellular—in addition to intracellular—signaling and regulation in synthetic biology’s favorite model organism.

The original motivation for this project was to create a model system that will resemble the natural hormone regulatory systems of the body. Typically, these regulatory systems are responsible for maintaining normal functioning of vital human bodily processes including stabilizing blood glucose and cortisol levels. Breakdowns of these regulatory systems, as exemplified in diseases such as diabetes, hyperthyroidism, and Cushing's disease, represent many of the major obstacles facing mdoern medicine. The original intent of the project was to create an analogous model of one of these regulatory systems in E. coli, showing one plausible framework to serve as a scaffold for further research that could one day be used to present a solution to one or more of these diseases.

Project Design

The Caltech iGEM team plans to use the principles and methods of synthetic biology to create a model system that will follow the design in the picture below. The gene circuit has been designed so that "Cell 1" will produce a signaling peptide upon induction with aTc. This signaling peptide will then attach to the receptor of "Cell 2," triggering a very simple signal transduction pathway leading to expression of some target gene that, for our testing purposes, will be the reporter protein GFP. The quorum sensing systems being imported into the E. coli cells come from Gram-positive species of bacteria, which minimizes the possibility that their activity will interfere with or be interfered with by E. coli's endogenous signaling and reception systems but also introduces the challenge of trying to implement the relevant membrane proteins in an environment that significantly differs from their native environments (owing to the differences in membrane composition between Gram-positive and Gram-negative bacteria).