Team:TU Eindhoven/Project

This year’s iGEM team of the Eindhoven University of Technology focuses on a fundamental problem in the application of genetically modified bacteria: bacteria are not suited for many environments. For example: local bacterial production of medicine has a promising future as a medical treatment, but the human immune system still is a big limiting factor for this new technology. Another field that would greatly benefit from more resilient bacteria is the bioreactor industry; bacteria that can survive in high pressure and temperature environments can help increase efficiency of reactors.

To create such resilient bacteria the 2014 team has designed a ‘plug and play’ system using copper free click chemistry to attach different chemical groups to create bio-layers on E. Coli cell membranes. Circularly permuted OmpX (CPX), an outer membrane protein, was mutated to contain an azido-functionalized unnatural amino acid. CPX functions as an anchor for any DBCO functionalized molecule to click on to. The polymers used in this project were designed to form hydrogels , which enables the bacteria to have antifouling properties.

With our team’s biomedical background in mind, an anti-fouling chemical layer for use in the human body was chosen to test the ‘plug and play’ system. An anti-fouling hydrogel has to have little to no interaction with the human immune system, thus preventing immune responses caused by the presence of bacteria. Dibenzocyclooctyne Polyethylene glycol 10kDa (DBCO-PEG 10kDa) was chosen as the molecule to click onto OmpX to form the hydrogel because it has good anti-fouling properties and the modular length allows for easy testing on a smaller scale.

Our goal is to genetically engineer an E. coli bacteria strain in which each bacterium is able to produce a hydrogel capsule around its entire cell membrane, with the help of microfluidic techniques, in order to evade the immune system. This is visualised in Figure 2. A criterion that must be met is the fact that this engineered E. coli must produce a degradable capsule, either enzymatically or after a certain induction. The advantages of this technique are a possible gelation from the inside toward the outside (a more homogeneous gelation process), a controllable cell growth (only one bacterium per capsule), and the bacterium will be able to control its own polymerisation process enzymatically – this will result in more controllable drug release.