The Study On Mechanism Of Neutral Microaerophilic Fe(?) Oxidation In Paddy Soil

Geochemical iron cycling is one of the most important geochemical processes in the soil,the iron cycle process affects the important matter cycle processes such as carbon cycle,nitrogen cycle,hydrogen cycle and so on.The iron cycle process includes ferrous oxidation and iron reduction.In the neutral,microaerophilic environment,microaerophilic Fe???-oxidizing bacteria?FeOB?can oxidize ferrous iron into ferric iron,while the inorganic carbon is assimilated into organic matter,and to obtain the energy required for growth.Iron oxide produced by the iron oxidation process plays an important role in the degradation of pollutants in the environment.On the one hand,Iron oxidecan adsorb heavy metals in the environment,on the other hand,it acts as an iron reduction substrate to produce active Fe???that it has a significant effect on the degradation of contaminants.In this study,firstly,we use the gel-gradient tube method to enrich the microaerophilic FeOB,andstudy the three parts of ferrous oxidation,carbon assimilation and microbial community.Secondly,the effects of substrate on microaerophilic FeOB were investigated in the process of domestication and culture of different substrates.Furthermore,we investigated the effect of domestication on the oxidation rate,carbon assimilation amount and microbial community.Lastly,the effects of the products of iron oxidation on the degradation route and efficiency of pollutantswere investigated.The main conclusions are as followed:?1?To explore the iron oxidation and carbon assimilation capacityofmicrobial community,and microbial community composition,gel-gradient tubes with FeS or FeCO₃ were used to enrich microaerophilic FeOB from paddy soil.The results showed that the gel gradient tube culture method could successfully enrich the microaerophilic FeOB which belong to the inorganic autotrophic microorganism,they can drive ferrous iron oxide while assimilating inorganic carbon.This study mainly found some typical nitrate-dependent iron oxide bacteria,such as Pseudogulbenkiania and Magnetospirillum,the result shows these microbes have the potential to use ferrous iron and assimilate carbon in microaerophilic environments.?2?The effects of two different substrates on microbial growth,ferrous oxidation and carbon assimilation were investigated.The microbial growth,iron oxidation rate and carbon assimilation ability of FeCO₃ treatment were better than FeS treatment.In addition,with the increase of culture generations,the bacterial growth,iron oxidation rate and carbon assimilation ratio were significantly decreased,the result shows the relative abundance of non-dominant microbes was significantly reduced,the sequencing analysis also confirms this view.?3?The study reveal the effect of the product of iron oxidation on the degradation of pollutants and the degradation efficiency in the environment.The results show that the addition of electron donor citrate was beneficial to the reduction process of iron.The participation of ferrous iron significantly improved the degradation efficiency of organochlorine pollutants in the environment.The electron donor could change the route of transformation of pentachlorophenol,weakening the process of biological removal chloride,while strengthening the microbially mediated chemical dechlorination process.