Abstract: Ammonia-oxidizing bacteria play an important role in material cycles and water purifying processes in aquaculture ecosystems. In the present study, the screening of bacteria with capability to remove ammonia nitrogen from sludge on the bottom of an aquaculture pond was carried out, and the bacteria isolated were identified by biochemical tests and molecular methods, then, which were used for treatment of ammonia nitrogen in wastewater from breeding of Macrobrachium rosenbergii. The results showed that the isolated strain YX0703 with capability to remove ammonia nitrogen was Ochrobactrum anthropi, which was able to grow on both inorganic and organic nitrogen medium; Strain YX0703 not only had ammonia oxidation activity, but also had the ability to convert NO3- into NO2-, then convert NO2- into N₂. Moreover, strain YX0703 carried nitrite reductase K gene (nirK). The determination of minimal inhibitory concentration (MIC) indicated that strain YX0703 was resistant to cephalosporins, but sensitive to some antibiotics, such as quinolones, meropenem and tetracycline; the removal rate of ammonia nitrogen in wastewater from breeding of Macrobrachium rosenbergii were 96.98% and 97.44%, respectively, when shaker speed was 150 r·min^-1, at 25 and 30 ℃. These results suggested that the isolated strain YX0703 was capable of using inorganic or organic nitrogen, which also had activity of ammonia-oxidizing and denitrification, and was useful for removal of ammonia nitrogen in wastewater from breeding of Macrobrachium rosenbergii.

Key words: ammonia-oxidizing bacteria, Ochrobactrum anthropi, denitrification, biodenitrification, nitrite reductase K gene