Enrichment Culture Of Nitrifying Bacteria And Ammonia Monooxygenase Gene Fragments By Pcr Amplification

Nitrification, performed oxidation of ammonia to nitrate by nitrifying bacteria is a key process in the cycling of nitrogen and an impotent component of modern wastewater treatment. Chemolithoautotrophic nitrifying bacteria have many unfavorable physiological characteristics, namely, slow growth, small biomass and susceptible to environmental factors. To remove high ammonia-nitrogen concentration in wastewater from refineries, we directly enriched nitrifying bacteria of activated sludge via optimizing enrichment conditions (temperature > pHU NH4+-N concentration). The results showed that the number of nitrifying bacteria after 6 weeks enrichment increased 32.8 times and nitrification rate improved 2.76 times than that before enrichment.Ammonia-oxidizing bacteria which oxidize ammonia to nitrite is a key group of nitrifying bacteria. The population of ammonia-oxidizing bacteria is variable with the different environment. The gene of amoA in ammonia-oxidizing encodes the active-site polypeptide of ammonia monooxygenase which catalyzes the oxidation of ammonia to hydroxylamine. We designed a pair of primers special for the amoA gene by comparing the known amoA gene sequences and used PCR to amplify the amoA gene fragments. The results showed about 490bp DNA fragments were amplified.. Because the amplified products is specific to the P -subclass of the Proteobacteria , the amplification of the amoA gene may be a powerful molecular tools for detecting and analyzing ammonia-oxidizing communities in environment.