Heat Induced 'Light Bulb'

We aimed to engineer Escherichia coli so that it increases expression of a fluorescent protein (sfGFP) when an electrical current is passed through the growth medium, via the use of inducible promoters that respond to the heat-stress response created by the conversion of electrical energy to waste heat.

We designed two parts (BBa_K1895000 and BBa_K1895006) which respond to the heat-stress in two different ways:

  1. BBa_K1895000 contains the E. coli htpG promoter. RNA polymerase requires the stress response sigma-factor (σ32) to initiate transcription of genes downstream of this promoter. σ32 is produced by cells when under different forms of stress, one of which is heat. This composite part also contains a modified BioBrick compatible σ32 coding region (the gene rpoH, BBa_K1895001) which will create a positive feedback loop to the PhtpG promoter, therefore increasing the expression of the downstream reporter gene sfGFP and the fluorescence of the cell.
  2. BBa_K1895006 contains the dnaK promoter which, like PhtpG, is transcribed via binding of RNA polymerase by σ32. PdnaK is placed upstream of the BBa_0034 RBS and BBa_I746916 sfGFP.

To see our results click here

Arabinose Controlled Variable Resistor

We aimed to create a biological “variable resistor” by modifying the E. coli’s natural systems to allow for controlled ion uptake. In order to do so, we looked at the work carried out by the 2011 Tokyo-NokoGen iGEM team who used the smtA gene from Cyanobacteria and inserted it into a strain of E. coli. SmtA is thought to play a role in preventing heavy metal toxicity by binding excess heavy metal ions such as Cadmium (II), as characterised by Tokyo-NokoGen, or Zinc (II).

We took the smtA gene, (BBa_K519010), and put it under the control of a PBAD promoter, induced by the presence of L-arabinose, making our BioBrick BBa_K1895999. This should allow us to control the uptake of zinc ions by adding or removing L-arabinose, resulting in control over the resistance of the LB media.

To see our results click here

Microbial Fuel Cell

We aimed to look at different ways of improving the voltage output of a microbial fuel cell. At first we looked at yeast microbial fuel cells with the help of Dr Ed Milner, Dr Paniz Izadi and Professor Ian Head, but after talking with PEALS we decided to move away from using yeast and looked at working with E. coli instead.

For inspiration we looked at the Bielefeld 2013 iGEM Team . One of the issues we noticed with their design was that their porin overexpression protein was taken from Pseudomonas fluorescens and so the pores size was too large for the E. coli to handle. We changed this by overexpressing E. coli’s natural porin producing genes ompF, BBa_K1895004. Bielefeld also had issues with cell growth due to the metabolic stress of using a T7 promoter. To improve this part we used a PBAD promoter to allow the cell population to grow before inducing the porin over-expression, BBa_K1895005.

To see our results click here