The Horizontal Gene Transfer Between Cyanophage And Cyanobacteria And Their Genetic Diversity

At present the eutrophication of waterbodies worldwide becoming more and more serious. The incidence of cyanobacterial blooms is increasing, which pose serious risks for human and animal health, aquatic ecosystem sustainability. Dianchi Lake is the largest lake in the Yunnan-Guizhou Plateau, a lake of serious eutrophication. In recent years, the government invested the massive funds to improve the water quality, but cyanobacterial blooms still outbreaking frequently. As a specific infected viruse of cyanobacteria, cyanophage has a very important role in aquatic ecosystems and can be use as a controlling factor in cyanobacterial blooms, which was considered as a promising biological algicide. More and more research has been in the phylogenetic diversity of cyanophages and cyanobacteria and their genetic relationship.In this study we take the Dianchi Lake as our object, collecting water samples in the same place every month.According to environmental factors and composite index of water bodies,we have a preliminary study of genetic diversity and the genetic relationship and horizontal gene transfer between cyanobacteria and cyanophage.We collect water samples in Dianchi Lake at the same location every monthl and measure the water temperature and pH value and the other biochemical parameters. Combinaing the composite index of the Dianchi Lake, we found that:the pH value in Dianchi Lake changed little in a year, but has remained at a very high value; the entrophication in Dianchi Lake was mainly due to excessive total nitrogen content, andtotal phosphorus sometimes excessive; the cyanobacteria phenomenon in Dianchi Lake was different as season changing.We study the cyanobacteria and cyanophage in water samples in use of molecular biology, establishing the phylogenetic tree of16S-23SrRNA ITS to analyze the genetic diversity of the cyanobacteria, and combinaing the the phylogenetic tree of psbA to analyze the genetic diversity of cnanophage.we found that:1,the main type of cyanobacteria was Microcystis, included Microcystis aeruginosa, Bloom Microcystis, Microcystis wesenbergii, and a small amounts of Anabaena and Nostoc, indicating that the rich genetic diversity of cyanobacteria in Dianchi Lake. The temperature and other environmental factors changed in different seasons resulted in different type of cyanobacteria.2,The cyanophage sequences located in the many branches of the phylogenetic tree, showing the rich genetic diversity of cyanophage in Dianchi Lake, the main type of cyanophage was cyanophage of Microcystis aeruginosa snd little Synechococcus cyanophage and the type of cyanophage was great changed in different seasons.The cyanobacteria and cyanophage psbA gene was amplified and established the phylogenetic tree of cyanobacteria and cyanophage psbA at the same time.According to the phylogenetic tree, we analysised the genetic relationship and gene transfer between cyanobacteria and cyanophage. The result showed that:the psbA gene in the cyanophage was originated from the cyanobacteria as the convinced values in phylogenetic tree was relatively low, we concluded that the cyanophage can mediate the exchange of psbA in different cyanobacteria.The horizontal gene transfer of psbA in cyanobacteria and cyanophage occurred frequently.Through the above research, we have a preliminary understanding in the main types and the genetic diversity of cyanobacteria and cyanophage, and have a preliminary analysis of the horizontal gene transfer of psbA between cyanobacteria and cyanophage in the Dianchi Lake. The result in this study can make us have a better research on the evolutionary history of the cyanobacteria and cyanophage, and provide theory of evidence in the cyanophage governancing cyanobacteria.