Characteristics And Biochemical Effects Of Indigenous Iron Reducing Bacteria In Hetao Basin,Inner Mongolia

High arsenic groundwater,as a worldwide issue,poses severe health risks to local people,and therefore it is of great significance to seeking the source of groundwater As in the affected areas.As an important component of high As aquifer system,indigenous iron-reducing bacteria lead to the reductive dissolution of iron?oxyhydr?oxide,releasing arsenic adsorbed on iron minerals into groundwater.In the present study,the Hetao Basin,a typical inland basin hosting high As groundwater,is selected as the study area.Based on field test,laboratory experiment and the advanced molecular biology technology,the study investigated the chemical characteristics and microbial community characteristics of groundwater system,isolated pure iron reducing microorganisms,and assessed their characteristics of iron reduction capacities.The following conclusions are obtained.?1?Results of 16S rRNA gene sequencing showed that Proteobacteria,Bacteroidetes,and Firmicutes were the top three phyla in groundwater microbial community,and the microoganisms of the relatively high abundance at the genus level were Aquabacterium,Flavobacteriaeae,Pseudomonas,and Desulfurivibrio.The highest abundances of microorganisms in the sediment microbial community were affiliated with Proteobacteria,Actinobacteria,Firmicutes,Bacteroidetes,Chlorofloxi,and Acidobacteria,while at the genus level,the relatively high abundance were from Pseudomonas,Arthrobacter,Actinobacteria,and Noviherbaspirillum.?2?Eleven pure cultures capable of iron reduction were obtained from the groundwater and sediment samples via enrichment and isolation,which belonged to Bacillus?including B.subtilis,B.cereus,B.circulans,B.wiedmannii,B.thuringiensis?,Enterococcus?including E.casseliflavus and E.faecium?and Paraclostridium?including C.bifermentans,P.benzoelyticum,and R.lituseburensis?.?3?Representitive B.subtilis and R.lituseburensis had ability of reducing both dissolved Fe?III?and solid Fe?III?.Iron reducing abilities of R.lituseburensis are stronger than those of B.subtilis.R.lituseburensis and B.subtilis were able to reduce dissolved Fe?III?at the rates of 1.5*10^-9 and 1.3*10^-9mM Fe?III?/cell,respectively,and ferrihydrite at the rates of 764*10^-6 and 774*10^-6?mol/(cell*g_ferrihydrite),respectively.