Isolation and Identification of an Aerobic Denitrifying Bacterium

The present study was aimed to isolate an aerobic denitrifying bacterium from environmental samples.The collecting water samples were enriched and domesticated,the bromothymol blue (BTB) selective medium were used for screening.Based on the aerobic denitrification activity,ammonium and nitrite nitrogen removing ability,the strain DG-3 was isolated from the sample.The strain was identified according to its aerobic denitrification ability,morphological,physiological and biochemical properties and phylogenetic analysis of its 16S rDNA sequence.The results showed that the reduction efficiency of strain DG-3 was up to 75.57% under aerobic conditions with initial NO₃^--N concentration of 138.63 mg/L,and the accumulated nitrite appeared during the process of denitrification,the max concentration was 2.06 mg/L.The morphology of strain DG-3 was with an average size of (1.7 to 2.8)μm×(0.6 to 0.7)μm and a pale yellow surface.DG-3 was identified as Pseudomonas mendocina by morphological and biochemical characteristics and molecular properties.It could be concluded that DG-3 had an aerobic denitrification ability with removing ammonium and nitrite,which showed a great potential in nitrogen wastewater treatment.