Team:Utah State
Abstract
The cheese industry generates billions of dollars each year, and no wonder—cheese is delicious! One of the greatest difficulties that the cheese industry faces is bacteriophage (virus) infection, which kills bacteria used in the manufacture of cheese. The industry utilizes a variety of approaches to deal with this problem, each having their own drawbacks. The 2015 USU iGEM team is implementing a synthetic biology approach to design and create phage resistant Lactococcus lactis, a commonly-used cheese starter bacteria. The genetic mechanism behind this phage resistance functions by pairing a promoter that is activated in the presence of phage with a kill switch to terminate infected cells before phage are able to propagate.
Project Description
Bacteria are used for a number of important purposes within the bioprocess and food industries. One notable example is the fermentation of dairy products in order to create cheese and yogurt. One problem that practitioners of bacteria fermentation deal with is attack by bacteriophages—viruses that infect bacteria. Many different techniques are used to control phage infection, including prevention of phage contamination by routine cleaning of the fermentation areas and rotation of cultures, employment of phage resistant strains of bacteria, and efforts to minimize opportunities for the appearance of new strains of phage. With the rise of molecular biotechnology, it is possible to create new types phage resistant bacteria by stacking genes with defense systems into the same strain and genetic construct. The dairy industry has funded research of this sort to creating phage resistant strains of lactic acid bacteria.
Building on research aimed at the creation of phage resistant lactic acid bacteria, the 2015 Utah State University iGEM team is using synthetic biology to create a strain of Lactococcus lactis that is capable of detecting, reporting, and fighting against phage infection, specifically the bacteriophage P335 from the Siphoviridae family. These bacteria will work by using a promoter from the virus itself, known as the cro promoter system, which will activate when the phage is present. In a construct where the bacteria will report the presence of phage so the culture can be stopped before the infection spreads, a GFP or RFP that is functional in the L. lactis bacteria will be placed downstream of the promoter. This will allow technicians to measure the fluorescence levels present in the culture to gain an indication of phage presence at any given time. In the version where the bacteria are able to fight against the infection, a suicide system will be placed downstream from the promoter system, which will cause the bacteria to die before the phage is able to fully form, preventing further spread throughout the culture.
In addition, another goal for the USU team is to test the viability of promoters and fluorescent proteins that were designed for lactic acid bacteria in L. lactis.
See our page for the interlab study at [https://2015.igem.org/Team:Utah_State/Interlab]