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Characteristic Of The Nitrate-Dependent Iron-oxidizing Aquabacterium Parvum B6

Posted on:2017-09-12Degree:DoctorType:Dissertation
Country:ChinaCandidate:X X ZhangFull Text:PDF
GTID:1311330536481103Subject:Environmental Science and Engineering
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The nitrate-dependent Fe(II)oxidation(NDFO)process of Fe-oxidizing bacteria(FOB)was studied for the existing contamination of water resources in China.Via strain screening,efficiency investigation,metabolic mechanism anal ysis and bioreactor establishment and operation,the metabolic characteriscs and mechnism of the Aquabacteria were explicated for the first time.In this study,lab-preserved FOBs classified in different species were determined via controlled tests,and a type stain B6 from Aquabacterium parvum was selected as the experiment subject since its excellent performance of nitrate reduction,Fe(II)oxidation and cell proliferation.Via batch cultivation under anaerobic condition,Aquabacterium parvum B6 could achieve desirable anaerobic NDFO efficiency after inoculattion,and the biomass could also reach its maxium number of approximately 2.73×105 cell/m L.Influence of different factors on the efficiency of NDFO of strain B6 was also investigated.After comprehensive comparison,strain B6 cultured in medium using yeast extract or Na Ac as carbon source could achieve higher nitrate reduction rate and Fe(II)oxidation rate.Meanwhile,using glucose as carbon source would benefit the cell growth whilst Na-citrate,as carbon source,had a negative effect on the NDFO efficiency of strain B6.Further,according to the results of response surface methodology(BBD),initial p H was the most significant factor that affect the nitrate reduction of strain B6.Meanwhile the initial p H and C/N ratio had drastically influence the Fe(II)oxidation.Optimization Numedcal Solution was utilized to optimize the NDFO efficiency.The whole genomes of Aquabacterium parvum B6 was sequenced with Illumina Hi Seq 2000 system.According to the results by RAST annotation server,the genome size of strain B6 was 4 592 999 bp and the GC content was 65.3%.The functional genes were divided into 27 categories.252 genes,236 genes,59 genes and 22 genes were related to Protein,Carbohydrate,Nitrogen and Iron metabolism,respectively.The annotation results indicated that strain B6 possess a metabolic pathway of nitrate→nitrite→Nitric Oxide→ Nitrousoxide under anaerobic condition.This process was closely related to the encoding genes of NarG,Nar H,Nar J,Nar I,q Nor,Nnr S,DNR and Nnru.The Fe-S cluster of Nar,the heme C of Nir as well as the q Nor were involved in the NDFO process of strain B6.A continuous up-flow bioreactor was established and stain B6 were added to the bioreactor as inocula to explore the application of microbial NDFO efficiency in process.Ammonia nitrogen variation,nitrate reduction,nitrite accumulation,Fe(II)oxidation and total Fe removal during the operation period were investigated.The total removal rate of nitrogen and iron of the bioreactor was 79.7% and 75.16% correspondingly.The nitrate reduction and Fe(II)oxidation rate of the bioreactor were 46.9% and 60.33% respectively for anoxic section.Namely,the reduction rate was approximately 0.07 mg NO-3-N/(L·h)by the anoxic section inoculated with strain B6.The up-flow bioreactor ensured the diversity of microbial communities in both section.The NDFO metabolism of strain B6 could be expected since its relatively dominant position(relative aboundance of 8.06%).Meanwhile,Bacillus(22.58%)which function as close substitutes was also enhanced in in anoxic section,ensuring the biological application of nitrogen and Fe(II)removal performance of the reactor.In aerobic section,microbes such as Sphingobacterium,Chryseobacterium,and Bacillus that conduct heterotrophic nitrification and aerobic denitrification metabolism developed into dominant status.
Keywords/Search Tags:biological nitrogen removal, nitate reduction, nitrate-dependent Fe(II) oxidation, genome sequencing
PDF Full Text Request
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