Members of the Thaumarchaeota are abundant in the ocean where they play a major role in the nitrogen cycle. The recent discovery of their involvement in the Anammox reaction explains a metabolic pathway leading to the assimilation of inorganic nitrogen by plants to make proteins. the fixation of atmospheric nitrogen gas to ammonia for use by plants. the conversion of inorganic nitrogen to nitrogen gas that is released to the atmosphere. the reduction of nitrite and nitrate in soils to nitrogen gas in the atmosphere. the decomposition of organic nitrogen to inorganic nitrogen..