Dinitrogen Production from Nitrite by a Nitrosomonas Isolate

A chemolithotrophic ammonium-oxidizing bacterium that was able to reduce ¹⁵NO₂⁻ to ¹⁵N₂ (m/z 30) while oxidizing ammonium under conditions of oxygen stress was isolated from stream sediments. Energy was derived from ammonium oxidation, as evidence by growth, with CO₂ serving as the sole C source. The organism was a gram-negative, motile, short rod that failed to grow either aerobically or anaerobically in heterotroph media. The organism was identified as a Nitrosomonas sp.