Molecular mechanism of anaerobic ammonium oxidation

Abstract

Two distinct microbial processes, denitrification and anaerobic ammonium oxidation (anammox), are responsible for the release of fixed nitrogen as dinitrogen gas (N(2)) to the atmosphere. Denitrification has been studied for over 100 years and its intermediates and enzymes are well known. Even though anammox is a key biogeochemical process of equal importance, its molecular mechanism is unknown, but it was proposed to proceed through hydrazine (N(2)H(4)). Here we show that N(2)H(4) is produced from the anammox substrates ammonium and nitrite and that nitric oxide (NO) is the direct precursor of N(2)H(4). We resolved the genes and proteins central to anammox metabolism and purified the key enzymes that catalyse N(2)H(4) synthesis and its oxidation to N(2). These results present a new biochemical reaction forging an N-N bond and fill a lacuna in our understanding of the biochemical synthesis of the N(2) in the atmosphere. Furthermore, they reinforce the role of nitric oxide in the evolution of the nitrogen cycle.

Towards A New Decision Support System for Design, Management and Operation of Wastewater Treatment Plants for the Reduction of Greenhouse Gases Emission

“…Indeed, the partial nitritation-anammox (PNA) process constitutes an alternative for nitrogen removal than conventional nitrification-denitrification over nitrate, since it requires up to 63% less aeration energy, does not require the addition of an external carbon source and the production of sludge and CO2 emissions are minimal [15]. Given that N2O is not involved in the anammox metabolism [16], it is generally accepted that anammox bacteria do not contribute to N2O emissions.…”

<b>Physicochemical monitoring of wastewater from a sugar and ethanol industry after bioaugmentation, with a proposal for reuse

“…Even though the DO concentration increased in Lagoon G, the Central Uptake remained below the minimum limit (≥ 4 g L force help preventing the formation of substances with undesirable odor, such as ammonia and hydrogen sulphide, for example, from anaerobic biological oxidations (Kartal et al, 2011).…”

State of The Art Strategies for Successful ANAMMOX Startup and Development: A Review

“…Instances of failures in pH control have resulted in unsuccessful attempts in ANAMMOX cultivation [12]. This usually leads to changes in concentrations of NH [8,55] [56]. NO could be produced from NH 2 OH and NO 2 --N by AOB and ANAMMOX activity, respectively, while N 2 O generated from NO by AOB activity [57].…”