Nitric oxide gets a new role

Abstract

Fertilizer runoff from farmlands can create algae blooms that cause hypoxic dead zones in rivers, lakes, and oceans. But the runoff can also lead to the release of nitrous oxide (N2O), a greenhouse gas that can also destroy the ozone layer. In soils and during wastewater treatment, microbial enzymes convert fertilizer ammonia (NH3) into other nitrogen compounds through a process called nitrification. Nitric oxide (NO) is a key intermediate in the nitrification pathway rather than a by-product, as previously thought, reported Cornell University researchers at the ACS national meeting. Postdoc Jonathan D. Caranto and his adviser, Kyle Lancaster, studied nitrification in Nitrosomonas europaea, which is the dominant ammonia-oxidizing bacteria species in wastewater treatment plants. One enzyme converts NH3 to hydroxylamine (NH2OH). Previously, researchers thought that a second enzyme, hydroxylamine oxidoreductase (HAO), then oxidized NH2OH to NO2–. Under anaerobic conditions, NO2– gets reduced to N2O, yielding...