Characteristics of heterotrophic nitrifying bacterium strain SFA13 isolated from the Songhua River

Strain SFA13, with the ability to perform simultaneous heterotrophic nitrification and aerobic denitrification, was isolated from the Songhua River. Investigation of the phenotypic and genotypic characteristics of strain SFA13 revealed that its 16S rRNA gene sequence shares high similarity with that of Microbacterium esteraromaticum DSM 8609T (99.78 %). gyrB and recA gene sequences showed 92.40 % and 92.57 % similarity to those of M. esteraromaticum DSM 8609T, respectively, showing that strain SFA13 is a member of M. esteraromaticum. However, strain SFA13 showed distinctly different phenotypic characteristics from the type strain DSM 8609T. Strain SFA13 was negative for H2S production, β-fucosidase, hydrolysis of starch and Tween, utilization of salicin, l-alanine, d-fructose, d-galactose, d-glucose and d-trehalose; and positive for alkaline phosphatase, cystine arylamidase, acid phosphatase, naphthol-AS-BI-phosphohydrolase and β-galactosidase. The ammonium removal rate of strain SFA13 was affected by temperature, decreasing obviously as the temperature dropped from 30 °C to 10 °C. Even so, strain SFA13 exhibited a high ammonium removal efficiency at 5 °C. The highest ammonium removal rate was 4.41 mg NH4 + L−1 h−1 when the initial ammonium concentration was 61.63 mg L−1 at 5 °C. Excessive ammonium (more than 62 mg L−1) restricted the ammonium removal rate of strain SFA13. This strain could be used effectively to remove low concentrations of ammonium ion at low temperature.