Study On Diversity And Quantitation Of Denitrification Microbial In Rhizosphere Sediment Of Submerged Macrophytesin Lake Liangzi

Nitrogen cycling is one of the most important biogeochemical cycle in the estuarine ecosystem which is driven by microorganisms. It closely related to the environmental problems of lake eutrophication. Submerged macrophytes were believed to greatly influence nutrient cycle, whose rhizospheres also had a significant impact on denitrification process and its associated micro-organisms. In this study, rhizosphere sediments of Lake Liangzi submerged macrophytes were chosen as model systems. The structure and abundance of denitrification microbial community were analyzed using the DGGE, clone library and real-time PCR technique. Specifically, this study focused on the dynamic changes in structure and abundance of denitrification microbial community and the impact of environmental factors on the quantity of denitrification microbial. The main results of research are as follows:1. The results showed that rhizosphere sediments of Lake Liangzi submerged macrophytes were abundant in bio-diversity of bacterial community with the stripes of DGGE 27~38 in various seasons. Alteration of bacterial community structure was produced, and the bacterial diversity and population sizes were enhanced by rhizospheres of submerged macrophytes.2. Sequencing analysis showed that Nitrosospira and Nitrosomonas were two mainly found AOB groups in sediments of Lake Liangzi. And Nitrosospira had dominant position. AOA groups belonged to Thaumarchaeota which were divided two branches:watersediment and soil-sediment. Anammox bacteria was found in sediments of Lake Liangzi. And Candidatus Kuenenia occupied an absolutely dominant position. In this study we found an new strain which may belong Kuenenia, but its physiological and biochemical characteristics and whether had the anammox activity had yet to be confirmed by further studies.3. Quantitative analysis showed that the quantity of AOA which in rhizospheres sediments of submerged macrophytes had obvious increasing trend. Submerged macrophytes did not have a significant impact on the quantity of AOB, nir K-gene-bearing and nir S-gene-bearing denitrifiers, anammox bacteria. The abundance of denitrification microbial were high. Especially, AOA predominated over AOB, nir S-gene-bearing denitrifiers far outnumbered nir K-gene-bearing denitrifiers.4. Statistical analysis showed that Whether in winter or summer, AOA amo A gene copy numbers and OM showed significant positive correlation(in winter:r=0.914,P<0.05;in summer:r=0.970,P<0.01), which indicated that OM promoted the growth of AOA in rhizospheres sediments of submerged macrophytes. In winter, there was significant positive correlation relationship between NO3- and AOA(r=0.930,p<0.05); AOB amo A gene copy numbers was significantly correlated with the NH4+-N concentration in the pore water(r=0.955*,p<0.05), which showed that AOB amo A gene copy numbers were mainly controled by NH4+-N concentration; There was significant positive correlation relationship between p H and nir K(r = 0.933, p < 0.05); DO showed significant negative correlation with anammox bacteria copy numbers(r=-0.934*,p<0.05). In summer, AOA amo A gene copy numbers showed significant positive correlation with AOB amo A gene copy numbers in summer(r=0.893*,p<0.05), which indicated that a synergistic action may exist between AOA and AOB. There was significant positive correlation relationship between NO4+ and AOA(r=0.986,p<0.01);DO showed significant negative correlation with nir S-gene-bearing copy numbers(r=-0.930*,p<0.05).