Preliminary Study On Phylogenetic Diversity Of Cyanobacteria And Cyanophage Photosynthetic Gene PsbA In Eutrophication Lake

Cyanophage, as a kind of virus, which can specifically infect cyanobacteria, widely exists in marine and freshwater, and has played an important role in the regulation of aquatic production, diversity and community succession of cyanobacteria, biogeochemical cycle, and regulating gene transfer among microorganisms in aquatic ecosystem. Meanwhile, as a cyanobacterial-specific lethal factor, there is a great potential for cyanophage to prevent the cyanobacteria bloom and will not cause the secondary pollution, conducing to the balance of the aquatic ecosystem. As a kind of important biological resource, investigating the genetic diversity and its relationship with its host of cyanophage in different ecological environment, is of great significance for biological evolution.In this paper, we took water samples in Yunnan plateau lakes such as Dianchi Lake, Erhai Lake, Qilu Lake, Xingyun Lake, Yilong Lake as the research object, collected the samples on the fixed time and places and detected some related environmental factors, examined genetic diversity of cyanobacteria and cyanophage in each lake and analyzed gene transfer between cyanobacteria and cyanophage. Provide a theoretical basis for the treatment of eutrophication water such as Dianchi Lake. The main contents and results are as follows:1. The relationship between the cyanobacteria and water factors in Dianchi Lake. Taking Dianchi Lake as an example, several environmental factors we made are indicating that the natural elements have a significant impact for the growth and production of cyanobacteria, and further explained that the concentration of chlorophyll a was positively related with the temperature and pH values, and negative correlation with water transparency.2. The genetic diversity of cyanobacteria and cyanophage in Dianchi Lake. We take psbA as a target gene, do some research about the diversity of cynobacteria and cyanophage, the results showed that:(1) In the total 164 sequences, the major species of those are Microcystis, Anabaena, Synechococcus, Dunaliella and Melosira, which indicated the abundant genetic diversity in Dianchi Lake. In summer, Microcystis has a great species advantage because of the high temperature, however in other cold seasons, the associated algae are exsits. (2) A total of 146 cynophage psbA gene sequences in Dianchi Lake. The environmental parts are derived from the cynophage through the analysis of GC percentage content and amino acid triplet sequences motifs, and clustered into A to F 6 clusters, indicating the genetic diversity of cynophage in Dianchi Lake is rich. Compared with the marine, the psbA gene cluster in Dianchi Lake is more similar with the cyanophage communities of the Japan paddy floodwater; freshwater sequence homology is higher than that of marine sequence, indicates that the cynophage between freshwater and marine has great difference and unique type, and the evolution history among freshwater cyanophage and marine different are different as well.3. The genetic diversity of cyanobacteria and cyanophage in other lakes. (1) The cyanobacteria genetic diversity in other lakes:Erhai Lake (11 valid sequences of cyanobacteria psbA gene), Qilu Lake (17 valid sequences of cyano bacteria psbA gene), Xingyun Lake (19 valid sequences of cyanobacteria psbA gene), Yilong Lake (15 valid sequences of cyanobacteria psbA gene) also has their own psbA gene diversity, the major cyanobacteria are Microcystis, Aulacoseira, Synechococcus, Chlorella. The species diversity correlates with the temperature and other factors. (2) The cyanophage genetic diversity in other lakes:Erhai Lake (19 valid sequences of cyanophage psbA gene), Qilu Lake (25 valid sequences of cyanophage psbA gene), Xingyun Lake (34 valid sequences of cyanophage psbA gene), Yilong Lake (28 valid sequences of cyanophage psbA gen), which has its cyanophage genetic diversity of psbA gene.4. Gene transfer study. PsbA gene transfer among the cyanobacteria and cyanophage in this research mainly existed in Microcystis, Anabaena, Synechococcus, indicating that psbA gene in cyanophage derived from cyanobacteria; and the cyanophage can mediated gene transfer among the different class of cyanobacteria.Through the above research, we preliminary study the genetic diversity of cyanobacteria and cyanphage in eutrophic lake and give a analysis on photosynthesis gene transfer among the cyanophage and its hosts, and lay a theoretical foundation for the relationship between cyanobacteria and cyanophage, and the mechanism of control harmful algal bloom by cyanophage as well.