The Effect Of Zinc Pollution On Endophytic Bacteria Diversity And Infection Characteristic Of Sedum Alfredii

Sedum alfredii Hance is a Zn/Cd-hyperaccumulator native to China,which includes a diverse range of endophyte.Researches have proved that the influence factors of endophytic bacteria communities diversity in hyperaccumulating ecotype of S.alfredii includes environmental conditions,host plants and endophytic bacteria,especially soil environment.However,detailed knowledge concerning the community and diversity of rhizospheric and endophytic bacteria and infection characteristic associated with S.alfredii under the Zinc pollution is still far less than enough.Therefore,in this study,the differences of genetic diversity and community of endophytic bacteria between hyperaccumulator ecotype of S.alfredii were assessed using high-through sequencing technology?HTS?on the basis of DNA extracted from plants.The influence of soil environment on the community structures and biological roles of endophytic bacterial in the root,stem and leaf tissues of S.alfredii were also investigated.Colonization dynamics of plant growth promoting endophytic bacteria Pseudomonas fluorescens labeled with GFP??₈L₄-GFP?in rhizosphere soils and plant tissues of S.alfredii were investigated by the use of plate colony-counting methods in combination with the Dual photon confocal laser scanning microscopy?CLSM?.The reseach aims at laying a good scientific foundation for developing technogy of endophytic bacteria assisting phytoremediation of heavy metal contaminated soils.The main results were as follows:?1?In phylum level,Proteobacteria,Cyanobacteria,Bacteroidetes and Actinobacteria were the dominant phylum in S.alfredii stem and leaf samples,whlile Proteobacteria,Bacteroidetes and Actinobacteria were represented phylum in root samples.With the increasing Znic concentration of agriculture soil,the relative abundance of Bacteroidetes and Actinobacteria in stem and leaf were increasing,while the relative abundance of Cyanobacteria were decreasing and Proteobacteria were firstly increasing and then decreasing.Furthermore,in root samples,the relative abundance of Bacteroidetes and Actinobacteria were increasing,and the relative of Proteobacteria were decreasing.Meanwhile,the S.alfredii planted in the soil with 500mg·kg^-11 Zinc?Zn500?,the relative abundance of Proteobacteria,Bacteroidetes and Actinobacteriain in its stem and leaf were higher than those planted in Multi-metal Polluted soil?MMPS?.Instead,the relative abundance of Cyanobacteria were higher in MMPS.?2?At the class level,the dominant endophytic bacteria in S.alfredii were Cytophagia,Actinobacteria,Alphaproteobacteria,Betaproteobacteria and Cytophagia.With the increasing Zn concentration of agriculture soil,the relative abundance of Cytophagia,Alphaproteobacteria and Saprospirae in leaf were increasing,while the relative abundance of Betaproteobacteria were decreasing;in stem,the the relative abundance of Alphaproteobacteria were increasing,while the relative abundance of Cytophagia and Actinobacteria were decreasing and Betaproteobacteria were firstly increasing and then decreasing;in root,the relative abundance of Actinobacteria,Alphaproteobacteria and Cytophagia were increasing,while the relative abundance of Betaproteobacteria and Saprospirae were firstly increasing and then decreasing.At the same time,relative abundance of Alphaproteobacteria,Betaproteobacteria and Actinobacteria planted in the Zn500 were higher than those planted in MMPS.?3?At the genus level,Streptomyces,Flavisolibacter,Sphingomonas,Paucibacter,Rubrivivax?Citrobacter,Ralstonia,Pseudoxanthomonas,Acidovorax,Caulobacter,Burkholderia and Agrobacterium were the major bacterial class in S.alfredii.Combining Canonical Correspondence Analysis?CCA?and Heatmap?Spearman correlation?showed:The impact factors of the community structures of endophytic bacterial of S.alfredii were investigated,including the ecotypes of zinc content in plant,heavy metals levels and nutrition in rhizosphere soil.The relative abundance of Cupriavidus,Ralstonia,Pseudonocardia,Xanthomonas was mainly affected by Zn content in leaves and soil;in stems,Acidovorax,Sphingomonas,Achromobacter and Flavobacterium were shown to be positively related to Zn concentration of stems and its soil;in roots,Burkholderia and Rhizobium were related to Soil Zn and root Zn concentration.?4?The results of plate colony-counting methods showed marked strain?₈L₄^-GFP can invasion and colonization of S.alfredii,but the effect of colonization were different among root,stem and leaf.At the same sampling time,the count of?₈L₄-GFP were rhizosphere>root>stem>leaf.Besides,mature stems and leaves were the better places for further research.Dual photon confocal laser scanning microscopy results showed that marked strain?₈L₄^-GFP can be observed in the root,stem and leaf of the S.alfredii somaclone.At the plant tissues level,the count and strength of?₈L₄-GFP were rhizosphere>>root>stem>leaf;At the organization level,the strain?₈L₄^-GFP were mainly distributed at the root epidermis,and vascular tissue of the stem and leaf;at the cellular level,its were mainly distributed in intercellular space.Therefore,it is preliminarily indicated that the endophytic bacteria were grown and colonized the S.alfredii by staying away from the high pollution of zinc.In conclusion,the endophytic bacteria diversity of hyperaccumulating ecotype of S.alfredii were changed with the Zn pollution and soil property;meanwhile,the endophytic bacteria were grown and colonized the S.alfredii by staying away from the high pollution of zinc.