Regulation of reactive nitrogen removal in wastewater by viruses

In order to sustain the global food-energy-population dynamic of the anthropocene, mankind is ever-increasingly converting unreactive dinitrogen (N2) to reactive N (Nr), which then results in a cascade of positive (food and energy for people) and negative (damage to people, climate, biodiversity, and environment) impacts as Nr is distributed throughout Earth systems. To protect Earth’s ecosystems and drinking water supply and to mitigate climate change the discharge of Nr to the environment must be reduced. Even though wastewater treatment helps to reduce the load of Nr released to the environment, the wastewater treatment industry is still one of the major Nr-polluting sectors. Viruses are an important, but poorly explored, component of this system, reaching 10–1000-fold higher concentrations than in other aquatic systems. We propose that viruses are significant yet poorly understood regulators of efficient removal of Nr in wastewater treatment systems. The proposed project will bridge gaps of knowledge about the importance of viruses for Nr conversion processes in wastewater by specifically focusing on the interplay between host selectivity, alteration of host metabolism and abundance, genetics, and ecology of viruses from wastewater treatment plants. Making use of culture-independent techniques such as DNA-and RNA-SIP-targeted metagenomics and metatranscriptomics, as well as culture-dependent methods including physiological assays of newly established viral cultures the proposed project will deliver knowledge to what extent viruses regulate the removal of Nr from wastewater via symbiotic or lytic interactions with nitrifiers and denitrifiers. The outcomes of the project will provide fundamental insights to viral ecology and inform efforts for more efficient and sustainable operation of wastewater treatment plants.