The Study On Abundance And Diversity Of Ammonia-oxidizing Archaea In Tea Orchard Soil

Ammonia-oxidation is responsible for the rate-limiting step of nitrification in a wide variety of environments and plays a central role in the global cycling of nitrogen. Ammonia-oxidizing archaea(AOA) represent a substantial component of microbial communities in aquatic and terrestrial environments.However,its abundance and diversity has until recently remained unclear in tea orchard soil.Here we selected tea orchard soil of different ages and unveiled the abundance and composition of soil AOA by using quantitative real-time polymerase chain reaction,cloning and sequencing approaches based on amoA genes.These findings are assumed to improve fertilizing and management of tea orchard soil.The main results are as Follows:1.We found that pH was an important factor of net nitrification.When pH was 5, the net nitrification were 0.308,0.272,0.356 respectively;when pH was 4,the net nitrification increased to 1.365,1.146,1.659;when pH was 3,the net nitrification were 1.365,1.146,1.659,which was the most high value among them.The abnormal result may be due to the high-intensity fertilization in tea orchard soil.2.The abundance of AOA in all soil samples were determined by quantitative real-time PCR based on amoA genes.Population sizes of AOA in tea orchard soil were big.The 50y tea orchard soil had the most big number with 2.05×10~7,2.84×10~7, 3.04×10~7 copies per g dry soil.The second one,10y tea orchard soil,had 1.5×10~7, 9.4×10~6,9.8×10~6 copies per g dry soil and the 2y tea orchard soil had 3.5×10~6, 2.7×10~6,5.6×10~6copies per g dry soil,which was the least.On the other hand,the amoA genes of AOB couldn't be amplified maybe due to its absence or small amount in the soil.It is suggested that AOA dominated in tea orchard soil.Considering the strong nitrification in the soil,we assumed that AOA played an important role in nitrification in ecosystem.3.We selected 18 samples with different restriction-enzyme digestion profiles and sequenced.Polygenetic analysis of amoA gene fragment and the M-TRFLP data before showed that,GU396251,GU396242,GU396250,GU396241,GU396243 had the highest copy numbers of AOA amoA genes among the soil.It may play an important part in the nitrification in tea orchard soil.