Screening And Identification Of Antimony Oxidizing Bacteria And Their Effects On The Migration And Transformation Of Antimony In Soil

Antimony(Sb)is a highly toxic heavy metal element in the natural environment.The reserves and production of Antimony in China are in the forefront of the world.People pay more and more attention to the harm of high antimony pollution area to human health.Microorganisms play an important role in the geochemical cycle of antimony,which can determine the morphology,toxicity,migration and transformation of antimony.Antimony oxidizing bacteria have the ability to convert the more toxic Sb(III)to the less toxic Sb(V).Therefore,it plays an important role in bioremediation of Sb pollution.Traditional microbiological methods were used to screen antimony resistant strains in soil samples from typical antimony contaminated mining areas,and their classification status was identified.The effect of aerobic antimony oxidizing bacteria on the migration and transformation of antimony in contaminated soil was explained by simulating groundwater and soil multi-media environment.It provides basic data for the study of the mechanism of microbial participation in the geochemical cycle of antimony and the remediation of antimony resistant organisms in soil.The main research contents are as follows:Firstly,nine antimony resistant bacteria were isolated from typical high antimony contaminated soil by aerobic enrichment with 1 mol·m^-3 Sb(III),and their classification status was identified by morphological,physiological and biochemical tests,PCR amplification,16S r DNA sequence analysis,phylogenetic tree construction and other methods.Nine bacterial strains were identified to belong to three different genera,and one bacterial strain with good growth was selected from each genus and named as Acinetobacter sp.LX12,Rhizobium sp.LX14,and Pse?domonas sp.LX16,respectively.Experimental results of antimony resistance showed that strains LX12 and LX16 could both tolerate 2 mol·m^-3 Sb(III),and LX14 could tolerate 1 mol·m^-3 Sb(III).All three strains could tolerate at least 10 mol·m^-3Sb(V).The experimental results of antimony oxidation show that under aerobic conditions,strain LX12 and strain LX14 co-cultured with 100 mmol·m^-3Sb(III),the oxidation efficiency of Sb(III)was 5.3?mol·d^-1 and 3.8?mol·d^-1,respectively.Strain LX16 had a higher oxidation efficiency of Sb(III).The oxidation rate of Sb(III)is close to 100%in 3 days,and the oxidation rate is 29.5?mol·d^-1.The whole genome of bacterium LX16 was sequenced,and the reported antimony oxidation gene aio A was not found in bacterium LX16.This strain may contain unknown antimony metabolism and oxidation mechanism,which needs to be further studied.Finally,strain LX16 was co-incubated with antimony contaminated soil to explore the effect of strain LX16 on antimony migration and transformation in soil.On this basis,two groups of experiments were carried out,the control system(antimony contaminated soil only)and the addition system(antimony contaminated soil and antimony oxidizing strain LX16).Antimony in soil was analyzed by morphological extraction,X-ray diffraction analysis(XRD)and Raman spectroscopy.The results showed that strain LX16 oxidized Sb(III)on the surface of soil particles,and the bacteria and soil interacted to produce Fe-Mn oxide and Fe OOH.The adsorption capacity of Sb(V)in soil was enhanced,and the fixation of Sb(V)in soil in the form of strong adsorption state was promoted.The release amount of Sb(V)from solid phase to liquid phase was significantly reduced,and the fluidity of Sb in soil was reduced.LX16 has a faster oxidation rate of antimony and can significantly reduce the fluidity of antimony in soil.Therefore,strain LX16 has potential application value in the remediation of contaminated soil in antimony mining area.