Team:Guelph/Description
Antibiotics are antimicrobial compounds used to treat bacterial infections by eliminating bacteria or inhibiting their growth and/or reproduction. Sometimes, bacteria are capable of reducing or eliminating the effectiveness of the antibiotic and therefore have a greater chance of survival. These bacteria are then more likely to replicate and produce more bacteria with this same capability. This ability to resist the effectiveness of an antibiotic is known as antibiotic resistance. Increasing antibiotic resistance may lead to complications when treating infections that occur because of an illness or as a result of surgery. A study commissioned by the UK government predicted that by the year 2050 more people will be dying from antimicrobial resistance than are currently dying from cancer 1 . This crisis is becoming increasingly difficult to manage as more and more microbes are being exposed to antibiotics in the environment. Currently, tetracycline is one of the most commonly used broad-spectrum antibiotics in the world and has an amplitude of agricultural applications. Each year, of the roughly 60,000 tons of antibiotics are used for livestock globally, nearly 6,000 of those tons were tetracycline in the United States alone 2. In order to effectively slow down and minimize the damage of the antibiotic crisis, countries, groups and individuals must make a concentrated effort to monitor antibiotic usage and show restraint on when to use them. In efforts to combat the antibiotic resistance crisis, our team decided to create a biosensor to detect antibiotic levels, starting with tetracycline.
A biosensor will be a step in the right direction with regards to monitoring antibiotic use. A biosensor will allow for a rapid and efficient test of presence of antibiotics with a simple bacterial reporter system. For our biosensor proof of concept we decided to start with the detection of tetracycline as it is the most commonly used antibiotic. The biosensor we will create will consist of two actions: the detection of tetracycline which will be followed by a response. This response will be a colour change in the engineered bacterial cells through the utilization of the violacein pathway. Violacein is a purple coloured compound that is the final product in a pathway involving the actions of tryptophan and 5 proteins 3. This enzymatic pathway, first discovered in the bacterium Chromobacterium violaceum, is a branching process which produces one of four differently coloured pigments depending on which enzymes are being expressed in the cell. For initial proof of concept will make work of the first four enzymes resulting in a pink or green colour change, as shown in figure 1. VioC’s expression, the enzyme controlling the resultant pink colour, will be induced by the presence of tetracycline. So if tetracycline is present, there will be a pink colour change, and if no tetracycline is present, the bacterial cells will be green, indicating the system is working, as shown in figure 2. The violacein pathway was also selected because it has the potential to be expanded to detect more antibiotics.
As students at the University of Guelph, an agricultural focused university, the agricultural antibiotic crisis is a theme that strikes close to home. We are surrounded by agricultural research in making crops better, and analysing the effects of different factors on crops. When looking more into agricultural research and antibiotic use we made the connection to microbiology research on antimicrobial resistance. Looking into it further we were shocked by how detrimental the antibiotic resistance crisis is becoming and wanted to fight back. Advances in agriculture and farming can only take place in a healthy and sustainable environment. Monitoring and understanding the effect of antibiotics and contamination of food products is a fundamental part of creating this sustainable environment. As such, we set off to find a way to create a time- and cost-effective diagnostic test for agricultural antibiotic levels, and how we decided to do this is with a bacterial biosensor.
Project Inspiration and Description
Antibiotic Resistance
Why a Biosensor?
Project Motivation
The use of the violacein pathway was inspired by iGEM Washington 2017’s work using the pathway to visualize metabolic processes in yeast. Having the genes for the enzymes of this pathway readily accessible through the iGEM Registry made working with the system possible.
Next: Design
