Team:Newcastle/Proof

Electrically Induced 'Light Bulb'

We aimed to engineer Escherichia coli that it increases fluoresce when an electrical current is passed through the growth medium, via the use of inducible promoters that respond to the heat-stress created by an electrical current.

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

  1. BBa_K1895000 contains a HtpG promoter which is induced by a sigma-factor (σ32). This sigma factor is produced by cells when under different forms of stress. This part also contains a σ32 coding region which should create a positive feedback loop and therefore increase fluorescence.
  2. BBa_K1895006 contains a DnaK promoter which is induced by dnaK, a product of other stress related responses within the cell.

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 Tokyo-NokoGen iGEM Team in 2011 who used 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), shown by Tokyo-NokoGen, or Zinc (II).

We took the SmtA part (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.

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 (link to their MFC page). 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. 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 overexpression. JOSH CAN YOU LOOK AT THIS!!!