Soil Bacterial Community Structure In Rare Earth Mining Area And Remove Characteristics Of Rare Earth-heavy Metals By Isolates

Unreasonable mining may bring serious metal pollution,which is mixed with complex metal elements.These metal elements enter the surrounding soil and water through floating dust,surface runoff and leachate,which may bring unpredictable serious consequences to the surrounding environment,animals,plants and human beings.Up to now,the effect of heavy metal on soil microbial communities has been reported,however,the effect of combined pollution of rare earth and heavy metal on soil microbiota remain unknown.Baotou Rare Earth Tailings Dam,due to incomplete mining,has brought about serious rare earth-heavy metal compound pollution,which provides us with good research materials.In this study,the bacterial community structures of 5 soil samples seriously polluted by rare earth-heavy metals and one relatively unpolluted-soil sample around Baotou Rare Earth Tailings Dam were analyzed by Illumina-Hiseq sequencing technique.At the same time,metal-resistant bacteria were isolated from the polluted samples,and their rare earth-heavy metal tolerance and metal removal ratio were analyzed.The results are as follows:1.Six saline-alkaline soil samples were collected,samples C were non-polluted,samples B1,B2 and B3 were seriously polluted by rare earth elements,samples B4 and B5 were seriously polluted by rare earth-heavy metal elements.The salinity of B1?2.25%?,B2?3.14%?and B3?8.36%?samples was significantly higher than that of other samples.2.At the genus level,the abundance of the many floras such as Trichococcus?B1, 11.6%;B5,14.7%?,Psychrobacter?B1,20.8%?,Carnobacterium?B1,7.2%;B4, 6.6%;B5,1.8%?,unidentified_OM1_clad?B2,9.5%?)Planomicrobium?B1,10.9%?in contaminated samples were higher than that of uncontaminated control C?<0.9%?;However,the abundances of Skermanella and Pseudarthrobacter in sample C were 2.5%and 3.5%,respectively,but they accounted for only 0-0.7% of the contaminated samples,indicating that the spatial heterogeneity of the bacterial community structure of the contaminated samples was large.3.A total of 16 isolates were obtained from rare earth-heavy metal contaminated soils,belonging to 6 genera?Bacillus,Rhodococcus,Micrococcus,Brevibacterium,Brevibacillus and Methylobacterium?.The MIC values of the representative strains for the four metal ions are as follows:the MIC of all strains for La,Ce,Pb and Zn were greater than 590 ppm,550 ppm,320 ppm and 250 ppm,respectively, they exhibiting strong rare earth and heavy metal tolerance.Among them, Methylobacterium sp.B4-3 has the highest tolerance to La and Ce?MIC>800 ppm?,and Rhodococcus sp.B2-2 has MICs of>800 ppm and>500 ppm for La and Pb,respectively.Potential new species Brevibacterium sp.B6-7 exhibits high tolerance to both rare earths and heavy metals?MIC>500 ppm?.4.Under 10%salinity,the adsorption capacity of Brevibacterium sp.B6-7 on La³⁺,Ce³⁺,Pb²⁺and Zn²⁺was 5.45 mg/g,3.53 mg/g,19.58 mg/g and 25.11 mg/g,respectively.These results provide a theoretical basis for understanding the effects of rare earth-heavy metal complex pollution on soil bacterial community structure and diversity,and provide strain resources for the removal of rare earths and heavy metals from waste water by bacteria.