Sequential nitrification by an Alcaligenes sp. and Nitrobacter agilis

The ecological importance of heterotrophic nitrification has been difficult to assess because of low levels of nitrification associated with this phenomenon. Nitrification by a soil isolate, an Alcaligenes sp., which oxidizes pyruvic oxime to produce up to 1867 mg nitrite-nitrogen/L, is described. Sequential nitrification with the chemoautotroph Nitrobacter agilis, ATCC 14123, resulted in nitrate accumulation and a concomitant decrease of the nitrite produced by the Alcaligenes sp. when the bacteria were jointly cultured. The ecological significance of such a sequential system is discussed.