Occurrence,Distribution And Sources Of Biopterin In The Jiulong River And Estuary System

Biopterin is one derivative of pteridine with two nitrogen rings.It is usually synthesized during the metabolism of Guanosine triphosphate.As Biopterin is the precursor of many key macromolecular substances such as folic acid,Vitamin B2,nitrate reductase,nitric oxide synthase and sulfite oxidase in biology,it widely occurs in all organisms including microbes,higher plants and animals.After pterin compounds were discovered,researchers focused on their medical application imcludimg diagnosing and treating diseases,such as cancer,viral infection and nephropathy.Measurements have been done in human urine,plasma and other media,while there was still no previous reports regarding Biopterin in natural waters.I therefore trned to develop the rmethodology of measuring Biopterin in natural waters,and then applied it for detecting its occurrence and distrnbution in the Jiulong River and estuary.By conducting laboratory experiments,I wanted to explored the relationship of microbial-metal elements-biopterin,in order to understand the association of small metabolite molecules with metal elements in biology.My dissertation will cover three aspects:1)developing the methodologyof measuring lopternn,and its application in natural waters;2)Measuring biopterin in Jiulong River Estuary,Xiamen Bay,and Jiulong tributaries(Xixi and Beixi):3)Explore the dynanics of pternn and metsl during laboratory culture of Synechococcus under manipulative nutrnent addition(glucose,vitamin C,and biopternn).The results of field investigation showed that Biopterin widely exists in natural waters 'with large spatial and temporal variations.The concentrations of cellular Biopterin was high in Summer(as high as 61.77 ng/L),low in Spring and Autumn and lowest in Winter(around 7.76 ng/L).Spatially Biopterin concentrations in fresh waters were higher than tnose in the saline estuary.The concentrations of Biopterin in the upstream were much higher than tihose in the downstream and Xiamen Bay area in Spring,Summer and Autumn,The results suggest that the main source of Biopterin may be related to increased microbial activities.Positive correlation between Chlorophyll,AOU and Biopterin showed that Biopterin is highly associated with microbial activities and phytoplankton productivity.The concentrations of metals including V,Cu?Mn and Fe in the high turbidity zone increased slightly,then they decreased along with seawater Sporadically high levels of dissolved metals also occurred in Xiamen Bay,which could be attributed to sedimentary releases under low oxvgen conditions.In the experiments of culturing SJynechococcus,cellular Biopterin showed with a dynamic pattern along with the growth of with the growth of Synechococcus.The concentration of Biopterin increased significantly at the initial stage,quickly reached at a high value,then declined at the plateau stage.Biopterin showed a re-growth at the later stage.The concentrations of Biopterin were also different during the culture experiments with addition of the following agents:Biopterin>Glucose>Vitamin C>Control.Under the addition of nitrate,it was found that the increase of nitrate promotes the growth of SynechococcusIn summary,I developed the methodology of measuring biopterin in natural waters for the first time,and observed a large contrasting spatial and temporal distribution of Biopterin in natural waters.By combing environmental parameters,I suggest that biopterin is highly associated to biological activities including bacteria and phytoplankton.