Soil bacteria that convert nitrogen gas into ammonia could one day replace synthetic fertilisers, if researchers can rewire their internal control systems to make them leak this nutrient into the soil. Modern agriculture depends on chemical nitrogen fertilisers, which are energy-intensive to produce and damage the environment through runoff and greenhouse gas emissions. Some soil bacteria naturally fix nitrogen from the air using an enzyme called nitrogenase, but they keep the resulting ammonia for themselves. This project aims to understand the regulatory networks that govern how bacteria manage their internal nitrogen supply, then use synthetic biology to modify those controls so that the bacteria export excess ammonia or amino acids to surrounding plants. If successful, the work could reduce agriculture’s reliance on fossil-fuel-derived fertilisers, lowering both costs and environmental harm. The researchers also plan to apply the same principles to develop solar-driven biotechnological processes for industrial production of nitrogen-containing chemicals. The project combines experimental measurements of proteins and small molecules with computational modelling and the engineering of new master gene regulators, all while studying how bacteria form beneficial associations with plant roots.
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We plan to address how the supply of one key nutrient for plant growth - nitrogen in a form that can be taken up by plants (i.e. ammonia) - can be supplied by soil dwelling bacteria. A lack of nitrogen supply to plants frequently limits their growth, and the use of chemically produced nitrogen fertilizers threatens the environment and is energetically expensive to produce. Hence alternative methods to supply fixed nitrogen that are not dependent on fossil fuels or the application of chemicals to the soil are desirable. We plan to investigate how the nitrogen economy of simple soil dwelling bacteria is established through the network of control systems operating to achieve optimal levels of ammonia within cells, and to modify these control systems to then allow the export of ammonia or amino acids to the soil and hence to plants. Ammonia will be produced by the action of the bacterial nitrogen fixing enzyme nitrogenase, and we will work out how the bacterial cell regulates this metabolic process in order to maximize its own resource use efficiency. This knowledge will allow us to rewire the regulatory control for the purpose of enhancing agricultural productivity.To date some simple first pass attempts have been made to exploit bacterial ammonia export for plant growth, and somewhat surprisingly these one offs show promise in that plant growth is enhanced in a manner suggesting reduced nitrogen from the bacteria is becoming available to support plant growth.Hence successfully refining ammonia export by bacteria holds great promise. Our work requires that we accurately quantify various key small molecules and proteins used to determine the cells nitrogen economy, and produce a scheme whereby we can intervene and create a situation where some of the nitrogenase derived ammonia is excreted from the bacterial cells to the outside without greatly sacrificing the growth and fitness of the nitrogen fixing bacteria. To do so we will use methodologies which capture the various players of the control systems in action, allowing us to work out where the major points of regulation occur and how they might be modified to gain an ammonia export function without losing the fitness of the organism. This approach requires that we combine experiments with modelling of the nitrogen control schemes, and also deploy synthetic biology tools to produce new master gene regulator proteins which will allow us to capture the control of the entire complex networks of genes needed for the cells management of its nitrogen economy. By combining these approaches with knowledge and parallel study of how soil dwelling bacteria establish close associations with plant roots and are competitive , and in particular how they gain carbon as an energy source from plants, we expect to be able to in a sustainable way improve nitrogen supply to plants in order to improve crop yields. In addition, we plan to utilize the knowledge and understanding that is gained in this project to also develop renewable biotechnological processes for industrial production of nitrogen containing chemicals that is driven entirely by solar energy.
Jacob Bundy (Co-Investigator)John Pinney (Co-Investigator)Martin Buck (Principal Investigator)Michael Stumpf (Co-Investigator)Patrik Jones (Co-Investigator)Philip Poole (Co-Investigator)Raymond Alan Dixon (Co-Investigator)
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