Toronto

From 2007.igem.org

iGEM Project: Bacterial Neural Network

Please see the Background link below for more on what a neural network is.

A visual abstraction of the system. Red light inputs pass through filter cells (grey in this image) and hit photoreceptors on the reporter cells (depicted by solar panels). The reporters sum multiple inputs and fluoresce (blue lightbulb).

Our project aims to build a bacterial (E. coli) neural network composed of two cell types, where filter cells (type A) modulate input to reporter cells (type B). The first cell type is stimulated with red light of a specific intensity and duration, and will turn blue in proportion to that "pulse" of light. Populations of type A will be physically mounted above those of type B, acting as a light filter. Type B cells are receptive to the same wavelength of light, and will fluoresce in proportion to the amount of light they receive.

Neural networks are unique in that their ability to signal both forward (type A influencing type B) and backward (type B influencing type A) results in the ability to learn. Training sessions can be performed with predefined inputs and outputs, and repeated iterations will increase the probability that giving the network an input will produce the desired output. Our neural network training functionality will be implemented through cell-cell signalling from type B cells to type A cells, adjusting the strength of the light filter.

Depending on the training strategy used, our neural network can learn to function as either an AND or an OR gate. Essentially, our neural network will be able to sum a number of inputs and provide a proportionate output. Once training is completed with a few inputs, we should be able to provide novel inputs to the network and produce appropriate responses. This is a step towards demonstrating fuzzy logic (as opposed to traditional digital logic) in genetic circuits.

For a more comprehensive description including genetic circuit diagrams, please see E. Coli Neural Network. (Updated proposal!)

Background: What is a neural network? (coming soon; in the meantime, here is the Wikipedia definition of a neural network)

Simulated Models

We are currently working on two types of simulations.

Ordinary Differential Equations

An example of the differential equations used to model the neural network. This set defines the luxR-eCFP pathway in the second cell type.

Monte Carlo Stochastic Simulation

This graph depicts the second cell type responding to light. The two shades of purple lines indicate two cell populations producing LuxI, while the red line indicates total HSL production. In our neural network, LuxI is produced in response to light input, and expression of LuxI controls the expression of HSL; therefore, this cell type can "add" the light inputs to produce appropriate HSL output.

Graph predicting interactions in the complete neural network.

Construction

Construction strategy: Using classical DNA transformation and ligation techniques, we plan to build six testing constructs to provide experimental constants for our simulated models of the neural network. The simulations will then assist us in optimizing our experimental conditions for training the final circuits. Building test constructs also results in reliable intermediate parts that can be used to quickly assemble the complete neural network.

Lab Notebook - watch our daily wetlab progress online

Design Updates - the circuit diagrams for the neural network and testing constructs

Lab schedule - the lab schedule is now obsolete. The most recent version is available at [http://igem.skule.ca/lab/schedule.htm BlueGenes lab schedules].

Lab Protocols - online versions of our lab protocols. These can also be found on our static site, igem.skule.ca.

The Team

What is BlueGenes? - a brief overview of who we are, and where the name comes from (not pants!)

Meet the Team - team roster, photos, and profiles

A Short History of Progress: BlueGenes 0T7 Timeline - because the lab notebook doesn't tell the whole story

iGEM 2006 Wiki: [http://parts2.mit.edu/wiki/index.php/University_of_Toronto_2006 Blue Water]. Of particular note is the lab notebook (click on Construction under Committees).

Sponsors

Sponsors

If you would like to support us, please go to [http://igem.skule.ca/finance/opportunities.htm Sponsorship] for more on becoming a sponsor.

Miscellany

Website: [http://www.igem.skule.ca igem.skule.ca] - other information about BlueGenes can be found here.

Contact Us: igem[at]skule[dot]ca