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Team:PennState/diauxie/intro
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Diauxie EliminationHormone Biosensors |
Introduction
There are currently a only few dependable transcriptional induction systems that are readily available for use in E. coli and other bacteria. Some common systems use proteins such as LacI and AraC to sense the level of sugars such as lactose and arabinose respectively. In both these cases the presence of glucose affects the amount of transcription promoted by each operator; in wild-type bacteria the genes downstream of these operators are involved with metabolism of the sugar associated with the control of that gene system. This phenomenon of preferential sugar usage for cell growth is called diauxie. In this project our goal is to introduce a new induction system that uses xylose as the inducer. To make this system unique, transcription will be activated in the presence of xylose regardless of the presence of glucose in the cell. This will create a novel and useful new way of initiating transcription that isn’t limited to cases where glucose is not a carbon source. In addition to creating a valuable new tool for the part registry, this project has useful applications in the bioproduction industry, including (but not limited to) conversion of biomass to ethanol using bacteria. Common biomass feedstocks used for production contain a 50:50 mixture of glucose and xylose. When cells are grown on this mixed carbon source, diauxie causes glucose to be used first, then depending on the process xylose is consumed or removed as waste. This leads to inefficiency in production, especially if a continuous process is desired. Separation of xylose from glucose is very costly, and so is the lag time when the cells are switching from glucose to xylose metabolism. The induction system we are creating would eliminate this problem by eliminating diaxuie, leading to more efficient production by using both sugars at the same time. |
