Welcome to iGEM Guelph 2019!

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Here’s what you need to know!

VioSensor: Developing an Antibiotic Biosensor as a Diagnostic Tool to Measure Tetracycline in Animal Products

Contemporary use of antibiotics in medicine and agriculture has resulted in the sharp increase of drug-resistant bacteria. These resistant bacteria pose risks to human and livestock health, as commonly-used antibiotics become less effective for treating infections. Additionally, if animal products contaminated with antibiotics are consumed by humans, there is a risk that the consumer’s intestinal microbiota will be damaged or create their own resistant bacteria. In light of this, antibiotic detection and monitoring in the environment and in animal products are of very current relevance. In our project, we’ve used synthetic biology to develop a bacterial system that can sense tetracycline and respond to its presence by producing a non-toxic biological pigment. The resulting system produces a visible colour change after induction with water, dairy, or meat samples that contain tetracycline. This project lays the groundwork for the development of affordable and sustainable biosensors that can detect other antibiotics.

Tetracycline Operon Repression and Activation System

TetR binds to the tetO sequence repressing the transcription of downstream genes. Tetracycline can bind to TetR causing a confirmation change resulting in TetR losing its ability to bind to tetO. This leaves the operator and promoter sequence open to RNA Polymerase binding and the transcription of downstream genes can begin.


pJKR-H-TetR (pTet) as our plasmid backbone. Designed by Rogers et al. (2015) this plasmid uses GFP downstream of the tetracycline promoter. Using GFP as the reporter for tetracycline presence requires fluorescent measurements which is not very applicable to applications outside of the laboratory. This is why we plan to modify this to contain visible colour pigments as the reporters of tetracycline presence in the system.

Violacein Biosynthesis Pathway

The VioABE enzymes convert L-tryptophan into the first intermediate which will spontaneously decompose into prodeoxyviolacein. If VioC is present, the intermediate is transformed into deoxyviolacein. VioD allows for the production of another intermediate which can result in two other colours and has potential for future expansion of the systems sensing capability. This figure was adapted from iGEM Washington 2017.

The VioSensor

The VioSensor comes in two separate components: the sample container and the reaction compartment. The sample container is a 5cm box with a hinged lid to provide a sealed environment for the biological reactions. The lid’s design includes a small protrusion that is forced into the container to ensure that there is no gap between the internal and external environment. The sample container component of the VioSensor can be 3D printed at home using the PLA filament, and the reaction compartment must be shipped from a supplier.

Check out the rest of the Wiki for more info!

University of Guelph iGEM 2019