Diversity And Driving Factors Of Endophytic Bacterial Communities Of Aquatic Plant Nymphoides Peltatum In Mountain Lake

Endophytic bacteria in plants have many biological functions,such as growth promotion,plant protection,bioremediation and so on.They are important components of plant micro ecosystem.Endophytic bacteria of aquatic plants play an important role in many ecological processes in lakes,however,compared with terrestrial plants,the understanding of the diversity pattern of endophytic bacterial communities of aquatic plants is far from enough.Therefore,studying the dynamic regulation of endophytic bacterial communities structure of aquatic plants in mountain lakes,revealing its diversity and its driving factors,has important scientific significance and theoretical guiding value for understanding the function maintenance of aquatic plants.In this study,the structure and diversity of endophytic bacterial communities in Nymphoides peltatum were studied through high throughput sequencing,in Mayinghai Lake of Shanxi Province.The characteristics of diversity changes of endophytic bacterial communities were analyzed,and the factors affecting diversity changes were discussed.Based on the null model of phylogenetic diversity,the assembly process of endophytic bacterial communities was analyzed.The source of endophytic bacteria was explored based on traceability analysis.The results showed that:(1)The species composition of endophytic bacterial communities varies in Nymphoides peltatum with different organs and seasons.The number of species in the endophytic bacterial community of Nymphoides peltatum in summer is as follows: leaves > stems > roots,and there are unique groups in different plant organs;in autumn,the order is stem > leaf > root,and different plant organs do not have unique taxa.In summer,unclassified＿f＿＿Comamonadaceae and Methylotenera were the dominant genera of endophytic bacteria in leaves and stems;norank＿f＿＿Rhodocyclaceae and Sideroxydans were the dominant groups of root endophytic bacteria.In autumn,Clostridium＿sensu＿stricto＿1 was the dominant genus of endophytic bacteria in leaves;Delftia was the main dominant genus of stem endophytic bacteria;norank＿f＿＿Rhodocyclaceae and Sideroxydans were still the most dominant groups of root endophytic bacteria.The number of species in the endophytic bacterial communities of Nymphoides peltatum increased in autumn,and the dominant genera such as unclassified＿f＿＿Comamonadaceae,Delftia,and Methylotenera bacteria had seasonal differences.(2)The diversity of endophytic bacterial communities varies in Nymphoides peltatum with different organs and seasons.Among different organs,the Shannon index of leaf endophytic bacterial communities was the highest in summer(P < 0.05),and the α diversity of leaf and stem endophytic bacterial communities in autumn was significantly higher than that of root endophytic bacterial communities(P < 0.05).The Shannon index of root endophytic bacterial communities decreased significantly in different seasons(P < 0.05),while the leaf and stem endophytic bacterial communities did not change significantly.There was a significant relationship between plant soluble protein content and α diversity of endophytic bacterial communities.For β Diversity,the spatial structure of leaves and stems endophytic bacterial communities was more similar than that of roots,and their community structure had obvious seasonal variations,while the seasonal differences in the spatial structure of roots were not obvious.There were significant relationships between the contents of plant soluble protein,total carbon and total sulfur with the β diversity variation of endophytic bacterial communities.Overall,changes in soluble proteins in different plant organs due to seasonal changes may be a major contributor to the changes in α diversity and β diversity in endophytic bacterial communities.(3)The source and construction process of endophytic bacterial communities varies in Nymphoides peltatum with different organs and seasons.The community construction of endophytic bacteria in leaves and stems was dominated by unknown random process.While the roots was dominated by the deterministic process of homogenous selection,and the relative proportion of deterministic process decreased in autumn.In summer,root endophytic bacteria were mainly derived from root epiphytic bacterial communities(70.67%),leaf endophytic bacteria were mainly derived from stem endophytic bacterial communities(75.83%),and leaf endophytic bacteria were also an important source of stem endophytic bacterial communities(59.49%).In autumn,root endophytic bacteria were still mainly derived from root epiphytic bacteria(88.07%),leaf epiphytic bacteria were the largest source of leaf endophytic bacteria communities(53.32%),and leaf endophytic bacteria were the main source of stem endophytic bacteria communities(58.41%).In general,the endophytic bacterial communities in different seasons were mainly derived from epiphytic bacterial communities,and the sources and proportions of endophytic bacterial communities in different organs were different.However,the endophytic bacterial communities in adjacent organs had strong mobility,and the surfaces of roots and leaves were important interfaces for the sources of endophytic bacterial communities.In conclusion,this study not only analyzed the diversity of plant endophytic bacterial communities by combining the characteristics of water,rhizosphere soil and different organs of plants,but also analyzed the effects of water,soil,plant physiological characteristics and seasonal changes on the diversity,source and construction mechanism of endophytic bacterial communities of aquatic plants.The results provide data support for revealing the mechanism of maintaining the diversity of endophytic bacterial communities in aquatic plants,which has important scientific significance and theoretical guiding value for understanding the functional maintenance of aquatic plants.