Our FerriTALE

The Problem

Enterohemorrhagic E. coli (EHEC) causes severe illness in over a quarter of a million people each year, costing us billions of dollars worldwide in food recalls and treatment. These bacteria normally live peacefully in the gut of cattle, but when they are present in the water, vegetables or meat that we eat, they can result in illness and even death. In the cattle population only a small number of animals, about 5%, produce the vast majority of the EHEC, around 95%, found in all cattle and the surrounding environment. These cattle with such high bacterial loads are known as "super-shedders" as they contain anywhere from 100 to 10,000 times as many colony forming units of these bacteria. The high amounts of EHEC being excreted into the cattle surroundings lead to prime opportunities for EHEC to contaminate ground water, vegetables and surrounding cattle in the same holding pen. In the case of other cattle, a contaminated hide of an animal increases the risk of spreading the contaminant to the meat where it could causing illnesses to consumers. If super-sheddering cattle could be detected prior to entering the processing plants, a significant risk for the contamination of water, vegetables, and meat could be eliminated.

Our Goal: to design and build a synthetic biology system capable of identifying EHEC super-shedding cattle.

The Solution

Before embarking on our project, we asked ourselves how does the industry views these challenges. This led to our systems informed design by initiating discussions with industry that we continued throughout the development of our project. We believe developing a product should involve the industry and end users input at all steps of development. This core belief in informed design has led us to build a system that can achieve scientific rigor and meet the needs the industry has indicated to us for a biosensor. To read more about our user-focused, informed design approach to human practices click here.

To detect EHEC bacteria in a sample we developed a unique detection strategy combining tools available in iGEM as well as the literature. We designed DNA binding proteins available in iGEM that allow us to capture sequences only found in the pathogenic E. coli coupled with a chemically modified protein nanoparticle that acts as a rapid catalyst to create a readable colour change in a matter of seconds. To aid in tuning our system we created a mathematical model to predict the amount of DNA binding proteins needed for varying levels of sensitivity, alongside two spatial models to demonstrating how our system works. Finally, we designed a physical prototype of our system and were able to obtain some preliminary data as to its functionality. More on the scientific details of our project can be found here.

In addition to the EHEC biosensor we have been working on, we felt the need to give back to the iGEM community as well. Early in the planning stages of our project our team looked into past projects and found a staggering number of biosensors. By joining forces with Paris-Bettencourt's iGEM team we created the first database of iGEM team-created sensors, SensiGEM. This tool will aid in streamlining the design process for future teams doing projects with the theme of a biosensor. To learn more about our collaboration click here.