Isolation and identification of ammonifying bacteria in the downstream waters of Baiguishan Reservior in Henan Province and conditions of degrading organic nitrogen

Abstract:

[Objective] The aims of the present study were to isolate and screen ammonifying bacteria, and to examin the conditions for their degradation of organic nitrogen. [Methods] Ammonifying bacteria were isolated from the micro-polluted raw water collected from the downstream water bodies of the Baiguishan Reservoir in Henan Province. The obtained nitrifying bacteria were studied for their capabilities to degrade organic nitrogen; The conditions for strain N24 to remove organic nitrogen were assessed by using single factor method. Strain N24 was identified by morphology, physiological and biochemical characteristics, and 16S rRNA gene-base phylogenetic alalyses. [Results] Four ammonifying bacterial strains were isolated from the collected water samples, The NH4+-N concentration reached 138.926 mg/L after 40 hours’ fermentation of strain N24. The optimal conditions for strain N24 to remove organic nitrogen were about 30?35 °C, initial pH 6.0, and medium volume 75 mL. Strain N24 was identified as Bacillus flexus (GenBank accession number: JX291240.1). Its 16S rRNA gene sequence had 99%?100% similarity with those of Bacillus sp. deposited in GenBank, and showed closest relatedness to Bacillus flexus IFO15717T (GenBank accession number: NR024691.1). [Conclusion] N24 is an efficient organic nitrogen-degrading Bacillus flexus; The present study enriched the microbial resources for organic nitrogen removal and provided a theoretical framework for the practical use of strain N24 in environmental engineering.

Key words:Ammonifying bacteria, Bacillus flexus, Organic nitrogen, Degrading conditions, Phylogenetic analysis