Phylogenetic Diversity And Temporal And Spatial Distribution Of G23Genes Of T4-type Bacteriophages In Freshwater Lakes Of Hubei And Yunnan Province

With high abundance and wild distribution in the aquatic ecosystem, virioplankton is the controller of the primary productivity and secondary productivity. The huge diversity is the important clue for the discovery of its ecological function. T4-type bacteriophage is the supreme exponent of virioplankton. And g23gene had been used as a marker for the investigation of its genetic diversity. Repports were more commonly seen in the habitats of sea, paddy fields and soil. Researches were sparse and scattered in freshwater lakes, and very rare in plateau lakes. In this study, sequences combining environmental factors were used to analysis the phylogenetic diversity and temporal and spatial distribution of T4-type bacteriophage in freshwater lakes. The sequences include1630g23gene sequences from lakes in HuBei and YunNan province. The g23gene sequences at different times (winter and summer) and space (plateau and plains, different levels of trophic habitats) and phylogenetic diversity of characteristics were systematicly explained based on sequences analysis, phylogenetic analysis and comprehensive statistical analysis methods integrating various interdisciplinary research tools, such as community ecology, quantitative ecology, molecular ecology and bio-informatics. Furthermore, differences among time scales and spatial scales were compared. The performances of differences and the conserved sites of different scales were found. Finally, attempts were carried out to reveal the differences caused by the distribution.The results were as follows:1, The g23gene of T4-type bacteriophage in freshwater lakes is quite different from other habitats. The mean identity compared with GenBank sequences was only73.41%and sequences which were already reported were32.57%-63.76%.2, There were differences in seasonal distribution of the T4-type bacteriophage g23gene in freshwater lakes. The phylogenetic diversity in winter was higher and more closely clustered than that in summer.3, There were differences in trophic level distribution of the g23gene of T4-type bacteriophage in freshwater lakes and should be separated from lakes in plains and plateau. The phylogenetic diversity in winter was higher and more closely clustered than that in summer. Phylogenetic characteristics of the T4-type bacteriophage g23gene were as follows:in plains, oligotrophic lake had the lowest phylogenetic diversity and the T4-type bacteriophage community was relatively phylogenetically overdispersed; mesotrophic lake had the middle phylogenetic diversity and the T4-type bacteriophage community was phylogenetically overdispersed of the maximum which meant far genetic relationships among species. In plateau, T4-type bacteriophage community of middle eutrophic lakes was phylogenetically overdispersed of the maximum which also meant far genetic relationships among species. TP could to the maximum extend explain the trophic level distribution pattern of the phylogenety.4, There were differences in elevation distribution pattern of the T4-type bacteriophage g23gene in freshwater lakes. Lakes in the plains had higher diversity than that in the plateau at light eutrophic and hyper eutrophic levels, and the rest trophic levels were just contrary. Light eutrophic lakes in the plains had the highest phylogenetic diversity, and so did middle eutrophic lakes in the plateau. T4-type bacteriophage community was phylogenetically overdispersed in the plateau, while the community was phylogenetically clustered in the plains.5, New "conserved regions" were found in the process of conserved points analysis. Besides the classical "conserved regions" which were known as the front12amino acid residues and the rear47amino acid residues, there were four other sections relatively conserved in the "hypervariable regions". And this four conserved regions were not continuous. The real meaning of the hypervariable regions were in those interval regions. The conserved sites were more frequently found in the interval regions other than in the "hypervariable conserved regions". Specifically, there were relatively conserved sites in different seasonal sequences. More conserved sites were found in the summer sequences than that in winter. And there were conserved sites only right in "hypervariable conserved regions" in summer sequences. There were also relatively conserved sites in different trophic level sequences. More conserved sites were found in the oligotropher and hyper eutropher lakes sequences than in others. And there were conserved sites only right in "hypervariable conserved regions" among light eutrophic lakes sequences. There were also relatively conserved sites in different elevation lake sequences. More conserved sites were found among the plains lakes sequences than pleaseu’s. And there were sites right in "hypervariable conserved regions" both among plains lakes sequences on the "Ⅳarea" and pleaseu lakes sequences on the " Ⅰ area".The results above had a favor of enriching the knowledge about virioplankton phylogenetic diversity in aquatic ecosystem and the means of virioplankton phylogenetic diversity. It also laid the foundations of awareness of ecological niche of virioplankton in aquatic ecosystems and its ecological functions.