Rapid enrichment and ammonia oxidation performance of ammonia-oxidizing archaea from an urban polluted river of China.

Ammonia oxidation is the rate-limiting step in nitrification process and dominated by ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). In the present study, a highly enriched culture of AOA was obtained from urban polluted water in Shahe River, Shenzhen, China. The optimum growth conditions were identified by orthogonal analysis as 37 °C, with pH 7.0 and initial ammonia concentration of 1.0 mM. Under these conditions, the highest abundance of AOA was obtained as 4.6 × 10⁷ copies/ng DNA. Growth of AOA in polluted river water showed significant reduction in ammonia concentration in AOA-enriched cultures without antibiotics after 10 days of incubation, while synchronous increase in nitrate concentration was up to 12.7 mg/L. However, AOA-enriched by antibiotic showed insignificant changes in ammonia or nitrite concentration. This study showed that AOB play an important role in ammonia oxidation of polluted river water, and AOA alone showed insignificant changes in ammonia or nitrite concentrations. Therefore, the ammonia oxidation performance of natural water could not be improved by adding high concentration AOA bacterial liquid. Image 1 • Optimum growth conditions of AOA were identified by orthogonal analysis. • Highest abundance of AOA was obtained by 4.6 × 107 copies/ng DNA. • AOB play an important role in ammonia oxidation of polluted river water. • AOA-enriched by antibiotic showed insignificant changes in NH 4 ⁺ and NO 2 ⁻. In this study, the optimum growth conditions of AOA in a polluted river were investigated. AOB also play an important role in ammonia oxidation in the river water. [ABSTRACT FROM AUTHOR]