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 two 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 the commonly used E. Coli chassis.