Fe???-mediated Microaerobic N₂O Reduction Characteristics Of The Type Strain Alsobacter Metallidurans SK200a-9

The nitrogen cycle and iron cycle are important biogeochemical cycles.Amount of studies demonstrate that microbes can take advantage of energy produced by using nitrate as oxidant to oxidize Fe???,therefore,new biological denitrification technology mediated by nitrate-dependent Fe-oxidizing bacteria has been widely concerned.However,there is very little research on N₂O,one of greenhouse gases that has significant effect on global climate change,produced in the process of anaerobic iron-oxidizing denitrification.In addition,the study of the microbial mediated Fe-N coupling production N₂O is still in its infancy.This research intends to study the denitrification physiological activity of N₂O in the product of Alsobacter metallidurans SK200a-9,a typical strain of potential new family Alsobacteriaseae.To confirm the function of nitrogen removal and predict the denitrification activity,PCR amplification and phylogenetic analysis of denitrification function gene of SK200a-9 were carried out.Following,the nitrate consumption,N₂O production and biomass of SK200a-9 using different carbon sources?glucose,succinic acid and acetic acid?in different oxygen levels were measured.What`s more,The effects of Fe???concentration on the denitrification efficiency,biomass and N₂O prodction of SK200a-9 with different carbon sources were studied.Eventually the effect of carbon source concentration on nitrogen removal efficiency,biomass and N₂O production with Fe???-oxidizing was studied.The main results are as follow:?1?According to the result of PCR amplification and phylogenetic analysis,it was indicated that SK200a-9 sequence include nirK gene which can code nitrite reductase,but not nosZ gene which can code N₂O reductase.It showed more than 94%identity to the nirK gene clones detected from paddy soil in Japan and farmland in LiaoNing Province,and these sequences formed an independent cluster.Since it showed identity less than 84%to Rhizobiales except Afipia?identity 90%?,it was classified to be an unknown nirK gene sequence.According to the above results,it was preliminarily predicted that the end product of SK200a-9 denitrification could be N₂O.?2?The N₂O product activity test of SK200a-9 with Fe???participating showed that it can play the denitrification reaction only in around 2%oxygen system with Fe???added,and N₂O production was about 1000?g/m³.The control without Fe???did not produce N₂O.?3?According to the N₂O product activity test of SK200a-9 with Fe???participating in micro-oxygen environment,it was indicated that the maximum growth of SK200a-9 and the optimal removal efficiency of nitrate nitrogen were detected on the condition that 0.89mM Fe???was added in the micro-oxygen system,with glucose,sodium acetate or succinic acid as single carbon source.The optimal removal efficiency of nitrate nitrogen was 46.82%,34.19%and 29.01%respectively.?4?On the basis of the N₂O product activity test of SK200a-9 with Fe???participating in micro-oxygen system containing variable carbon concentration,it was demonstrated that in the micro-oxygen system containing 0.89mM Fe???and83.4mM single carbon source,the best growth of SK200a-9 was detected,and the optimal removal efficiency showed 47.1%,34.3%and 26.09%respectively.Denitrification function of Alsobacter metallidurans SK200a-9,which was confirmed through studying the microbial mediated Fe-N coupling N₂O production in this research,provides the scientific basis to understand and control the new production way of the greenhouse gas N₂O,and it is essentially significant to reveal Fe-N coupling N₂O emission mechanism with microbial mediated.