A Study On The Variety And Characteristics Of Aerobic Arsenic-reducing Bacteria In Shimen Realgar Mining Tailings Of Hunan,China

Arsenic is an internationally recognized toxic heavy metals,which seriously threatens human's health.Arsenic reducting-bacteria(aARB)played an important role in the transformation of arsenic,which is of great significance for the treatment of arsenic pollution environment.The aims of present work were to(1)isolate aARB from the polluted soils,water and Pteris vittata L in the pollutional area of shimen country Hunan province.By enriching the aARB and comparing the effect of different samples on the kinds of isolates,it is believed that our knowledge of kinds and distribution of aARB will be enhanced;(2)identify the arsenate reduction ability and molecular mechanism of all aARB to explore their role in the arsenic geochemical cycling.Multiple of culture media and methods were employed to isolate aARB in our study.The arsenic-reducing characteristics such as arsenic reduction rate,accumulation rate,and resistance ability,and reducing genes(arsRDABC)were then determined.The main results are followed:(1)Twenty-four aARB with about 90% reduction were screened from arsenic polluted water and soils.Moreover,six genera,Leclercia,Raoultella,Kosakonia,Lelliottia,Yokenella,and Kluyvera were first time reported as families of aARB.After the arsenic resistance and mechanism exploration,it was found that the 24 aARB had high resistance of As(V)(80~300 m M)and As(III)(2~30 mM).The reduction genes in different bacteria were found to be distinct.In detail,arsBC was amplified in most isolted strains,which indicated that they were common reduction and resistance genes in aARB.(2)Twenty-three arsenic-resistant strains came from two phyla and ten genera were screened from the rhizosphere and tissues of Pteris vittata L.Most of the isolated bacteria were identified to be from the genus of Pseudomonas.The 23 isolated bacteria exhibited distinct arsenic resistance and reducing ability.The As(V)resistant concentration ranged from 80 to 300 m M and the As(III)resistant concentration was ranged from 5 to 30 mM.It is found that among these 23 isolated bacteria,four of them,Pseudomonas sp.S2,Pseudomonas sp.P3,Staphylococcus sp.S14,and Agrobacterium sp.P1 were able to remove 75%~79% of arsenic from the culture medium and reduce more than 81% arsenate to arsenite.The arsenate reducing mechanism of all 23 isolated bacteria was detected.The arsC gene,which is well-known for its involvement in arsenate reduction,was amplified from twenty-one strains,indicating its prevalence in arsenic-reducing bacteria.Finally,by comparation of aARB from different samples,we found that the aARB resistance from arsenic polluted soils were higher than Pteris vittata L.However,the accumulation efficiency from Pteris vittata L were stronger than that from arsenic polluted soils,indicating the tight connection between strains traits and samples.Above all,the exporation of the variety and characteration of aARB in different samples expanded our understanding of aARB diversity and emphazed the widespread distribution of aARB in high arsenic contaminated areas and its non-negligible driving force of arsenic transfer.