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. Because E. coli infection can be life-threatening, testing is a standard procedure in water treatment stations and slaughterhouses. Cell culture and PCR are gold standard techniques for E. coli detection and usually take 18 to 40 hours. Besides being time-consuming, current detection methods are based on samples of processed meat and the results are only available when the meat is already packed and on its way to the consumers. Pre-screening techniques can be very promising in preventing the distribution of contaminated meat. Their development requires a closer look on the cattle rather than the processed meat.

In the cattle population only 5% of animals produce around 95% of the EHEC 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. Super-shedders are kept in holding pens with normal cattle. By excreting high amount of EHEC, they can lead to contamination of ground water, vegetables and surrounding cattle. 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 in feedlots and prior to their entry 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 detecting EHEC, detecting super-shedding cattle, and preventing contamination.

The Solution

Before embarking on our project, we asked ourselves “how does the industry view this problem?”. Therefore we began discussions with the industry that continued throughout the development of our project. This information was then used to inform the design of our project. We believe developing a product-based project should involve both the industry’s and end-user’s input at all steps of development. Their input could then be incorporated into the design of the overall project, addressing their concerns and needs. This core belief in informed design has led us to build a system for the needs of the industry. 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 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 biosensor database, created exclusively by iGEM teams, named 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.