Cell-Free Biofilm Biosensor of Catheter related Urinary Tract Infections, Built using Biobricks that Exploit AHL Signalling Pathways in Biofilms

Urinary catheters are the major source of hospital infections worldwide and the second most common cause for bloodstream infections. Biofilm formation begins by the initial adherence of bacteria to the catheter surface that build a polysaccharide matrix. The internal communication is based on quorum sensing, involving small signaling molecules such as acyl-homoserine lactone (AHL). As part of the 2007 iGEM competition, we combined the principles of synthetic biology and the engineering cycle to produce ‘Infector Detector’. The design of this DNA construct, based on the MIT Biobrick Registry part F2620, consists of 2 main elements. The first is a constitutive Tet promoter, generating transcription factor LuxR. This binds to AHL, from the biofilm, providing the input of our biosensor system. The resulting AHL-LuxR complex activates the second part, a Lux promoter generating a fluorescent signal in the form of GFPmut3b, giving a detectable output. To avoid bacterial exposure in the clinical scenario, the biobrick was incorporated in an S30 E.Coli cell extract chassis - an in vitro transcription/translation system - as opposed to commonly used E.Coli chassis.

Imperial College has been successfully participating at the iGEM competition for 2 consecutive years. In 2006 they were first runner ups at the competition by engineering a molecular predation oscillator and also awarded a prize for best documentation and best part characterisation. In 2007 the Imperial team created and successfully tested a biofilm biosensor that could identify biofilm infections on urinary catheters. They also enhanced the Registry of BioBricks by adding a second, cell-free chassis, that could be used in the place of E.Coli. In 2007 they were awarded a gold metal for their overall contribution to the iGEM wiki and BioBrick Registry.