The Influence Of Zostera Marina On The Microbial Communities And The Preliminary Study Of Nitrogen Metabolism

Zostera marzina is a kind of perennial seagrass,which is an important primary productivity in marine ecosystem.Besides,Z marina has significant value in ecology and scientific researches.The previous research in our lab showed that the microbial communities in sediment were influenced by Z.marina,but the results failed to prove the differences induced by Z.marina directly.Therefore,the horizontal variation of environmental factors and microbial communities in sediment were detected to explore whether the variations were caused by Z.directly.Then the mechanism of nitrogen uptake of Z marina was also explored by observing the variations of uptake and the activities of key enzymes under different nitrogen resourses.Besides,a series of preliminary researches on the ammonium transporters were also done based on AMT1.5 and AMT2.3 in Z marina.1.The horizontal variation of environmental factors and microbial communities insedimentIn this study,all samples were collected from Shuangdao bay which is localed in Weihai,Shandong.Then the relevant physical and chemical methods and high throughput sequencing technology were used to analyse the environmental factors and microbial communities in sediment.The results showed that the sediment in Z marina rhizosphere has the characteristics of high-water sulfide(WS),high-total nitrogen(TN),low-sediment organic matter content(SOM),low-phosphate and low-inorganic nitrogen,and nitrogen may be the limiting factor of the growth of Z.marina in this bay.Although the composition of microbial communities in different samples has differences,all samples take the phylum Proteobacteria,Bacteroidetes,Chloroflexi,Planctomycetes and Acidobacteria as the dominate bacteria group.Besides,compared with the arrounding environment,the microbes in rhizosphere have the highest aboundances and diversities,and most of the special bacteria are related to sulfur or nitrogen metabolism.The correlation analysis shows that the microbial communities are mostly affected by SOM.Both of the content of SOM and the abundances of pathogenic bacteria in sediment of rhizosphere are lower than any other places.Hereby,the variations of microbial communities in sediment vegetated with Z.marina may result from the interaction between the plants and the cycle of nutrients,which includes the abundances and diversities of some bacteria increase or decrese.Therefore,the variations of microbial communities in sediment is relevent to Z marina directly.2.The influence of different nitrogen source test on the nitrogen uptake and key enzymes of nitrogen metabolism in Z marina.The results above show that nitrogen may be the limiting factor of the growth of Z marina.So this part was focus on studying the variations of uptake and the activities of key enzymes under different nitrogen sourses.The results indicate that the uptake of NO3-is inhibited by NH4+,while the uptake of NH4+is promoted by NO3-.In addition,NO3-can induce the activities of nitrate reductase,nitrite reductase,glutamine synthetase and glutamate synthase.However,NH4+can only induce the activities of glutamine synthetase and glutamate synthase.NH4+can significantly restrain the nitrate reductase activities and has no obvious effect on nitrite reductase activities.The results is same to terrestrial plants.Although the nitrogen uptake of Z,marina is different with terrestrial plants,the changes of key enzymes'activities is same to terrestrial plants.3.The preliminary research on the ammonium transporters in Z marina.Zostera marina has differences with terrestrial plants in using nitrogen type.NH4+is the main nitrogen form absorbed by Z.marina.In most plants,the transport of NH4+ is completed by ammonium transporters and there are no studies reported so far.In this study,the genes coded ammonium transporters were found from the complete genomic sequence obtained from NCBI.The basic characteristics of genes and amino acid sequences,expression pattern and the phylogenetic status were analysed in this study.The results suggest that the expression of genes ZmAMT1.5 and ZmAMT2.3 are induced by 10?M/LNH4+,and ZmAMTL5 and ZmAMT2.3 may play an important role in the transport process of NH4+.Moreover,ZmAMT1.5 may be a kind of high affinity transporter,while ZmAMT2.3 may be a low affinity transporter.The results of protein-structure show that both of ZmAMT1.5 and ZmAMT2.3 are hydrophobic proteins which are stable in primary structure.ZmAMT1.5 and ZmAMT2.3 have 9 and 11 transmembrane domains respectively,which are classic membrane transporters.However,the phylogenetic relationship between ZmAMT1.5 and ZmAMT2.3 is very far and their 3D structures have differences,which may be related to their functions.Our results show that the microbial communities are influenced by Z marina directly,which improve the provious results of our lab.They can not only have great significance in developing and utilizing the ecological functions,but also have high value in protecting and recovering of Z marina.Besides,the results of nitrogen uptake,key enzymes of nitrogen metabolism and ammonium transporters related to Z marina fill in the blank of AMT and increase the basic data of the mechanism of nitrogen metabolism in Z marina.