Team:NYU-AD/Description
Issue
In many developing countries, rapid urbanization leaves people with limited access to cooking facilities, resulting in a large dependence on reasonably priced and conveniently available street foods. These foods, however, pose a high risk of food poisoning due to microbial contamination. According to WHO statistics, food poisoning kills 420,000 people a year worldwide. One of the primary microbial contaminants is the Shiga toxin-producing E. coli O157:H7 (STEC). These particular pathogenic bacteria cause severe diseases in humans worldwide by secreting a toxin called Shiga-like toxin (SLT). Research shows that E. coli causes 73,000 illnesses in the United States every year. It is even estimated that STEC causes 2,801,000 acute illnesses worldwide annually, leading to 3890 cases of Hemolytic Uremic Syndrome, 270 cases of End-stage renal disease, and 230 deaths. Currently, there is no detection method for Shiga-like toxin outside of a lab setting, so consumers have no way of protecting themselves without strong legislation.
Project
Lack of action taken by governments and street food vendors in developing countries lead to the prevalence of street food-related illnesses, and call for the necessity of consumer awareness. Our project ultimately aims for a consumer-focused mechanism to detect Shiga-like toxins in foods.
Shiga-like toxins are exotoxins, which consist of a toxic enzymatic A subunit and a cell-binding B subunit. The latter binds to a globotriaosylceramide (Gb3) receptor, expressed on the surface of the target cells. This interaction is responsible for the toxin's entry into the host cell. Through our device, Gb3 will be expressed in non-pathogenic E. coli. When the receptor is exposed to the food sample, the SLT subunit B, if present, will bind to Gb3. Crosslinking will occur to stabilize the interaction. Next, a recombinant subunit B will be fused with a reporter and then applied to detect whether the Gb3 binding sites are available. If the binding sites are vacant, the sub-unit B will bind to them and elicit a signal, indicating the safety of the food sample.
In summary, we will be creating a portable device that would evaluate the safety of food by detecting a specific contaminant, Shiga-like toxin, for consumers who rely heavily on street food in developing countries in which there are weak food safety regulations.
Ideation Process
Before making our final decision, we explored an extremely diverse range of project topics such as blockage of oil pipes, controlling fruit ripening, detecting milk adulteration, biodegradable plastics, bioelectronics, preventing the coral reefs bleaching, bio-art, smoking, monitoring air quality, and more. After extensive research and intense discussion, we decided to move forward with the idea of detecting pathogenic SLT-producing E. coli in street foods. SLT is highly toxic due to its low LD50 and the A subunit’s protein synthesis inhibitory action, so it would have been too dangerous to work with given our lab environments. Keeping the validation process in mind, we decided to use only the SLT B subunit as our method of verification.
In addition to our main project, we have improved the characterization and validated the functionality of a previously submitted part by NYUAD iGEM team 2015. We have performed an Indole detection test to validate proper expression of indole of e.coli cells. Non-transformed cells were used as negative controls and pure indole solution served as positive control. Our experiment showed a highly significant colorimetric change corresponding to a high level synthesis of indole in transformed cells. Figures displaying this outcome and relevant protocols are shown both in our experiments and results pages.
