Identification of a denitrifying bacterium and verification of its anaerobic ammonium oxidation ability

A strain D-3 of denitrifying bacterium was isolated from an anammox reactor, and identified as Pseudomonas mendocina based on the morphological and physiological assay, Vitek test, Biolog test, (G+C) mol% content, and 16S rDNA phylogenetic analysis. As a typical denitrifying bacterium, strain D-3 achieved the maximal nitrate reduction rate of 26.2 mg/(L center dot d) at the nitrate concentration of 88.5 mg N/L. The optimal pH and growth temperature were 7.84 and 34.9 degrees C, respectively. Strain D-3 was able to oxidize ammonia under anaerobic condition. The maximum nitrate and ammonium utilization rates were 6.37 mg/(L center dot d) and 3.34 mg/(L center dot d), respectively, and the consumption ratio of ammonia to nitrate was 1:1.91. Electron microscopic observation revealed peculiar cell inclusions in strain D-3. Because of its relation to anammox activity, strain D-3 was presumed to be anammoxosome. The present investigation proved that denitrifying bacteria have the anammox ability, and the results have engorged the range of anammox populations.