Investigating widespread regulation of nitrogen assimilation at the level of RNA in bacteria

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Nitrogen is one of the key elements in biological systems since it is required in large quantities for the building blocks of life. Humans are rather limited in the sources of nitrogen they can use to live and grow, and we obtain nitrogen we need from complex organic compounds in the food we eat. By contrast, microbial metabolism is more adaptable and bacteria can capture the nitrogen they need from a range of simpler forms present in nature such as nitrate. In recent times, the amount of man-made nitrogen in the environment has increased dramatically due to industrial fixation of the relatively inert nitrogen gas present in the atmosphere. As the world population has grown, more intensive agricultural practices have been used to increase crop yields to meet this demand, including the widespread use of synthetic nitrate-based fertilisers in modern agricultural practice.Nitrate is highly soluble in water and readily lost from fields as run-off where it accumulates in rivers, lakes and oceans and provides an abundant nutrient for bacteria that are able to use it for growth. In agricultural fields the use of nitrate by soil microbes, instead of the crops for which it was intended, is not only economically wasteful but may also have a number of unintended consequences. One such consequence is predicted to be the increased consumption of dissolved organic carbon by particular bacteria in the environment. This poses a significant risk to the fertility and integrity of many soil types through catabolic breakdown of their organic constituents by nitrate-utilising bacterial populations. A significant decrease in soil organic matter would not only have a negative impact on the long-term sustainability of commercially valuable agricultural land, but increased microbial action on these carbon dioxide sinks may also contribute to global climate change.In this research programme we will address the role of a key gene we have identified that is essential for the use of nitrogen by the model nitrate-utilising soil bacterium Paracoccus denitrificans, which is widely studied in laboratories around the world. This gene is predicted to produce a regulatory protein that may control how bacteria use nitrate and carbon to grow. Understanding this process will enable us to develop strategies to minimise the impact of nitrate-utilising bacteria on our agricultural soils and the wider environment.