Engineering the bacterium Rhodopseudomonas palustris as a platform for electrosynthetic bioproduction

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In the context of global climate change and population growth, there is a need to replace fossil fuels with renewable sources of energy such as wind and solar power. However, if renewables are to be more widely taken up, new storage technologies are required to manage the fluctuations in the power they supply compared to demand. A second global challenge is meeting the growing demand for sustainably produced chemicals, both for fuels and for manufacturing.This project offers a comprehensive solution to the problems of energy storage and sustainable chemicals production, in the form of an electro-active biological material formed of genetically engineered bacteria. Electro-active bacteria can interact with metals in their environment and exchange electrons with their internal metabolism. Electrons that are taken up are used supply energy and to drive chemical reactions. Biological materials have the advantage of being self-assembling and self-repairing, and they capture carbon as they grow which decreases their environmental impact. The engineered bacteria would be grown in specialised electro-chemical reactors, allowing for secure containment and efficient use of land.This project will use the bacterium Rhodopseudomonas palustris, which is naturally electro-active and also has broad metabolic capabilities. This includes being able to harness light to produce energy, and the ability to capture both carbon dioxide (just as plants do when they photosynthesise) and nitrogen gases. The organism can also use electrical current to convert simple molecules into useful chemicals for fuels or manufacturing, or growth of the cell. We aim to engineer Rh. palustris so that it is more effective at taking up electrical current, and efficiently uses the electrical input to produce large amounts of desirable molecules. This would enable electrical energy to be converted into and stored as fuels such as hydrogen gas, or used for the production of useful molecules such as bio-plastics. Transfer of electrical current between cells and an electrode has already been demonstrated in Rh. palustris, showing the feasibility of this project. Synthetic biology is an approach to building designer organisms that uses standardised genetic parts and modular design to more predictably engineer their behaviour. This project requires the development of new genetic components for Rh. palustris. We will characterise libraries of genetic parts that will give us control over when and how strongly certain genes are expressed. We will also optimise methods for making genetic alterations to the Rh. palustris chromosome and expressing foreign genes. These tools will also be useful to other researchers who are working with Rh. palustris, and may be transferable to related organisms.We will also do fundamental research into how Rh. palustris takes up electrons, at the level of gene expression. This will inform us about how we might need to alter the gene expression to channel the organism's energy and metabolic pathways into useful activities. Again, this will be useful to other researchers looking to engineer Rh. palustris to produce desirable chemicals.Together, these genetic tools and data will enable us to introduce genes into Rh. palustris that give it the capability to effectively import electrical current, and to produce useful chemicals that it cannot naturally synthesise. We will also add genetic elements to control the switching between these different activities. Ultimately we aim to have integrated all these new functions together, producing a prototype organism for the conversion of electrical power to chemicals.