A study of nitrite-dependent dissimilatory micro-organisms isolated from oregon soils

Three specialized nitrite-dissimilatory microorganisms, found to be incapable of nitrate dissimilation, were isolated from Oregon soils. These isolates were designated as members of the genus Pseudomonas.Soil extracts stimulated nitrite dissimilation, with highest rates of activity observed with extracts from a manured soil. Nitrous oxide accumulation occurred with both nitrite- and oxygen-grown soil isolates during nitrite dissimilation in the presence of oxygen, whereas an isolate derived from a marine mud environment did not accumulate this intermediate when tested under comparative conditions.The soil-derived isolates were better able to adapt to changes between oxygen and nitrite as terminal electron acceptors, in comparison with the marine derived isolate. All isolates appeared capable of utilizing oxygen and nitrite simultaneously in their terminal respiration processes.Nitrous, but not nitric oxide was utilized as an electron acceptor by all isolates, and nitrite and nitrous oxide dissimilation was inhibited to varying degrees by cyanide, azide, and 2,4-dinitrophenol.Such infrequently studied specialized nitrite-dissimilating microorganisms, incapable of nitrate dissimilation, should be further investigated to better understand their role in nitrogen transformations, especially in manured soil environments.