Study On Abundance And Diversity Of T4-Like Bacteriophages In East Lake And Xiangxi Bay

The virioplankton refers to all kinds of virus particles in aquatic environments,including eukaryotic algae viruses,cyanophages and bacteriophage.Highabundance and phylogenetic diversity indicate the virioplankton play important role in aquatic ecosystem.The T4-like virus is an important representative of the virioplankton,and the g23 gene has been used as a molecular marker to study its distribution.In this study,the abundance and diversity dynamics of the T4-like virus in the East Lake and the Xiangxi Bay were studied,and the factors affecting viral abundance and diversity were analysised.1.Results from 2-years observation indicated that the abundance of T4-like phages showed different seasonal distribution pattern in the two environments.In East Lake,the highest and the lowest viral abundance were detected in winter and spring,while in Xiangxi Bay,the highest and the lowest viral abundance were observed in winter and autumnrespectively.Besides,there was no significant correlation between viral abundance and environmental factors.2.High throughout sequencing results basing on g23 gene sequence indicated that the OTUs acquired from the East Lake is less than that from Xiangxi Bay,but most OTUs from the East Lake containmore sequences than that from the Xiangxi Bay.This result suggests that the T4-like phages of the East Lake has higher richness and lower diversity than the population of Xiangxi Bay.3.Based on ? diversity analysis,the genetic diversities of g23 gene in the East Lake and Xiangxi Bay showed significant seasonal succession.There were no significant differences in g23 genetic diversity among different nutrient levels in the East Lake and different sites in Xiangxi Bay.Based on the correlation analysis between ? diversity and environmental factors,the richness of T4-like phages in the East Lake was significantly negatively correlated with temperature and dissolved oxygen.The richness of T4-like phages in Xiangxi Bay was significantly negatively correlated with the chlorophyll a.concentration.4.Based on ? diversity analysis,the temperature has the greatest impact on the T4-like phages diversity of Tuanhu and Guozheng sub-lakes,while nutrient concentrationis the main factor affecting the phage diversity in Guanqiao sub-lake.The T4-like phages diversity of Xiangxi Bay was affected by different environmental factors in different seasons.The main environmental factor affecting phage diversity in spring was l silicate,then chlorophyll a and temperature in summer,and orthophosphate in autumn sample and winter.5.Hierarchical clustering results showed that the g23 sequences from the East Lake are obviously divded into 2 clusters: spring-summer cluster and autumn-winter cluster.The sequences from different sites of Xiangxi Bay showed similar cluster pattern: sequences from the same season are more likely to cluster together.From the phylogenetic analysis,most phages from the East Lake and the Xiangxi Bay belong to different group and showed distant relative to phages from other environments,despite a few OTUs are closely relative to sequeces from the ocean,Lake Baikal and the French subalpine lake.