Bacterial Diversity And Screening Of Heavy Metal Tolerant Endophytic Bacteria Associated With Poplar In Mining Areas

With the development of high-throughput sequencing technology,the studies on microbial biogeographic distribution and their ecological function have attracted interdisciplinary attention.Microbial diversity plays an important role in maintaining the soil ecological integrity,as well as an important indicator for evaluating soil pollution.However,the understanding of bacterial communities in mine ecosystems,especially in mining areas polluted by lasting and multiple heavy metals,remains inadequate.In this study,a sampling survey was conducted on the remediation plots contaminated by multiple heavy metals in mining areas.It was found that the contents of Cd,Cu,Pb and Zn in the polluted area exceeded 2-200 times of the national risk screening value.Endophytic and rhizosphere bacteria of poplar,which has multiple heavy metal tolerant abilities,were sampled for 16S rDNA,and their community characteristics and related environmental factors were also studied.A large number of core species were found,and the variation of bacterial structures in the ecosystem polluted by heavy metals was revealed.The niche differentiation of bacterial communities in different habitats was further analyzed.The main research contents and results are as follows:Revealed the diversity and structure of endophytic and rhizospheric bacterial communities.The soil of mine tailing in Suxian District of Chenzhou and the bioremediation plant poplar were selected as the research targets.Soil samples from polluted and non-polluted areas of mining area and different plant tissue samples of poplar were collected for16S rDNA high-throughput sequencing.Bacterial community structure,composition and function of different sample groups were analyzed.The community structure characteristics and 48 dominant bacterial species were obtained.Study on the influence of environmental factors on microbes suggested that it was the co-effect of plant,soil characteristics,and heavy metals.The chemical indexes of soil and plant samples were analyzed and the heavy metal content was detected.The pollution status of soil and plant was evaluated,as well as the heavy metal transport capacity of plants.A number of related environmental factors were screened for the study of microbial communities,and the correlation between species and environmental factors was calculated by Pearson's correlation.The environmental correlation and selection strategy of the population were obtained,which provided the research basis for further screening of functional bacteria with matching environmental factors.Isolation and identification of endophytic bacteria in bioremediation poplar for the selection of heavy metal resistant bacteria were conducted.461 colonies were isolated from poplar root and stem samples after surface disinfection,80 single colonies were obtained by pure culture and propagation,and a number of culturable strains with tolerance to Pb,Zn and Cd.Physiological and biochemical tests were carried out on two dominant strains of heavy metal tolerant bacteria named Burkholderia sp.YG-3 and Enterobacter sp.YG-14.The MIC levels of the two strains reached 1300 mg L^-1and 1000 mg L^-1of Cd²⁺,1500 mg L^-1and 600 mg L^-1of Zn²⁺,and 2000 mg L^-1and 2000 mg L^-1of Pb²⁺.In high heavy metal concentration water,the removal rates of YG-3 and YG-14 of Cd²⁺reached 62%and 43%,respectively,and the removal rates of Zn²⁺reached 81%and 68%.It provides biological materials and basic data for the follow-up study of heavy metal tolerance mechanism.