Linking ecology, enzymes and ecosystems in the global nitrogen cycle
The global nitrogen cycle is of fundamental importance for our climate as well as agriculture, and both are facing significant threats due to environmental change. Anthropogenic input of synthetic ammonia-based fertilisers has a profound impact on the nitrogen cycle. Most soil ecosystems globally are nitrogen limited, necessitating ammonia-based fertiliser to achieve sufficient crop yield to feed the world’s growing population. However, circa 70% of fertiliser is lost through the activity of ammonia oxidising microorganisms, which contribute to the emission of the extremely damaging greenhouse gas nitrous oxide – a molecule with a global warming potential 300 times that of CO2, and also the most important ozone-depleting gas. 

Ammonia oxidising microorganisms are ubiquitous, highly abundant organisms. Despite their ubiquity and major environmental importance, they are some of the least well-understood microorganisms in the global nitrogen cycle. Several challenges contribute to the lack of our understanding: (1) Ammonia oxidisers are difficult to cultivate, (2) the molecular mechanisms driving their adaptation to different environments are poorly characterised, and (3) links between their cellular and physiological traits and the rates of nitrogen turnover are not understood. Consequently, it is difficult to interpret the ecological and environmental significance of many research findings. This research programme will bridge the gaps in our understanding of terrestrial nitrogen cycling using a combination of highly innovative methods. My research programme aims to reveal functions of uncultivated ammonia oxidisers and determine the important but overlooked role of cellular traits in nitrogen cycling rates in terrestrial environments. This study will provide a holistic framework of terrestrial nitrogen cycling from molecules to ecosystems and will deliver a major advance towards balancing the global nitrogen cycle.