Microbial Community Structure In Selenium-rich Soil Under Rice Planting And Rice Absorption Of Selenium

Selenium is an essential trace element for the human body,but also a beneficial element for plants.At present,domestic research on selenium mainly focuses on the behavior of selenium in the soil,plant selenium-enriched materials and nano-selenium materials,but there is a lack of research on the microbial community structure in selenium-rich soil and the absorption of selenium by rice.The selenium-enriched soil in Qintang District,Guigang City,Guangxi was selected as the research object,and the pot experiments using natural selenium-enriched soil and exogenous selenium were carried out.High-throughput sequencing technology was used to analyze the soil bacterial community structure,to explore the changes of soil bacterial groups under different selenium content before and after rice planting.Then determine the selenium content in plant various parts,and study the absorption of selenium by rice.The selenium-tolerant strains in the soil of each site were identified and the selenium removal ability was studied.The main findings of this article are as follows:(1)In natural selenium-rich soil,soil bacterial community composition with different selenium content before and after rice planting was roughly the same but the abundance changed slightly.At the phylum level,the dominant flora includes Proteobacteria,Acidobacteria,etc.At the genus level,Ornatilinea and Gp1 are the dominant flora.Soils with different selenium content had different abundance of microorganisms.When the soil selenium content was high,the relative abundance of Proteobacteria and Acidobacteria was low,the abundance of Chloroflexi,Ornatilinea and Anaeromyxobacter relative abundance was relatively high,and the abundance of Gp1,Gp3 and Gp7 was relatively low.Soil microbial abundance changes before and after rice planting.Compared with before planting,the relative abundance of Proteobacteria in the mature period was higher,and the relative abundance of Acidobacteria,Planctomycetes and Actinomycetes was lower.Natural selenium-enriched soils with different selenium content had no significant difference in rice plant height,yield,1000-grain weight aboveground biomass and underground biomass.The selenium content of each part of rice increased with the increase of soil selenium content.The selenium content of each part of plant was as follows: rice root>rice stalk>rice husk>rice.When the soil selenium content was high,the ability of roots to absorb selenium from the soil and the transfer ability of rice stalks to rice husks decreased.There was no significant difference between the primary transfer coefficient(PTI)of selenium from rice roots to rice stalks and the secondary transfer coefficient(STI)of selenium from rice stalks to rice.The selenium content of each selenium form increased with the increase of the total selenium content.There was a significant correlation between selenium content in rice and iron manganese oxide bound selenium in soil(P < 0.05),and extremely significant correlation with total selenium,exchangeable selenium and carbonate bound selenium(P < 0.01).(2)In the soil with exogenous selenium,the bacterial community composition of soil with exogenous selenium before and after rice planting was roughly the same.At the phylum level,the dominant flora was Proteobacteria,Chloroflexi,etc.At the genus level,the most dominant flora was Gp6.The application of exogenous selenium had an effect on the species abundance of the microbial community.Application of exogenous selenium reduced the relative abundance of Proteobacteria,increased the relative abundance of Chloroflexi,Gp6,Subdivision3＿genera＿incertae＿sedis,Gp3 and Sphingomonas.The abundance of the microbial community changed before and after rice planting.Compared with no planting,the relative abundance of Proteobacteria in the mature soil was higher,while Acidobacteria was lower.The increase of exogenous selenium content was beneficial to increase the rice yield,thousand-grain weight and above-ground biomass,but there was no significant difference in plant height,underground biomass(root).Rice roots,rice stalks,rice husks,and rice all increased after adding selenium content.The selenium content of each part of rice was as follows: rice root>rice stalk>rice husk>rice.In the absorption and transportation of selenium by rice,with the increase of soil selenium content,the ability of roots to absorb selenium from the soil decreased,the ability of roots to transfer selenium to rice stalks and the selenium enrichment capacity of rice stalks increased.The ability to transport selenium to the grain was reduced,selenium was more easily transferred to the inedible chaff.With the increase of selenium content,the total selenium content in the soil increased.The selenium content of the five forms raised with the increase of the total selenium content.The total selenium and soluble selenium in rice straw,rice husk,rice and soil the state,exchangeable and carbonate bound state,iron manganese oxide bound state,organic bound state,and residue state were all significantly correlated(P <0.01).(3)Four selenium-tolerant strains were screened out,labeled as A1,B4,C3,D6,and the selenium tolerance of the four strains reached 45000 μg/m L.A1 was identified as Comamonas,B4 as Lysinibacillus,C3 as Enterobacter,and D6 as Klebsiella,in the study of the removal rate of selenium by four strains,the C3 strain had the best removal rate in the range of selenium concentration of 0～4000 μg/m L,with the highest removal rate of 46.76%;in the range of 4000～5000 μg/m L,D6 strain had the best removal rate,the highest removal rate is40.04%.The four selenium resistant strains had the ability of selenium reduction,and could reduce sodium selenite to red elemental selenium.The results of this study provide a reference for the development and utilization of selenium resources.