This article examines the distribution of nitrogen-transforming bacteria in an artificial reservoir (pond) populated with aquatic higher plants of common reed (Phragmites australis) and cattail (Typha) for treating swine wastewater. In the pond occupied by Phragmites australis, 7 strains of ammonium oxidising and 14 denitrifying bacteria were identified, while, in the pond occupied by Typha, 6 strains of ammonium oxidising and 19 denitrifying bacteria were distinguished. A comparative analysis of bacterial count at various sampling points revealed their decrease along the artificial pond. Most of the bacteria strains oxidising ammonium were identified in the samples collected from the surface layer of the pond, while denitrifying bacteria dominated the bottom layer. The isolated microorganisms identified by 16S rRNA sequencing belonged to the genus Pantoea, Enterobacter and Bacillus. An artificial pond having aquatic higher plants is characterised by a diverse microbiota, whose composition strongly depends on the wastewater source rather than on the cultivated plant species. The ammonia transformation and denitrification capacity of isolated bacterial strains was determined. The highest conversion efficiency of ammonia (up to 56%) was observed for Enterobacter cloacae bacteria isolated from the surface layer of the pond. Denitrifying bacteria sampled from the bottom layer allowed for the reduction in nitrate content from 20 to 10 mg/L in 72 h. The obtained results confirm the role of bacteria in the treatment of wastewater against nitrogen-containing pollutants, with the average efficiency of removal of inorganic nitrogen compounds being 50%.