| Dissimilatory Iron Reduction(DIR),a kind of metabolism of microorganism,and Fe(Ⅲ) as the terminal electron acceptor was reduced to Fe(Ⅱ) in this process,coupled with the oxidation of organo/abio electron donors.DIR occurs generally in the natural anaerobic environment,where Dissimilatory Iron Reduction Bacteria(DIRB) exists universally.It is showed that DIR might be the earliest form of microbial respiration,according to geochemistry subject.Meanwhile,it was the earliest microorganism process besides other hot biosphere in former earth.Redox of iron oxides is prevalent in paddies,the model system in studying the redox process in natural eco-systems.oxidation reduction reaction is affected significantly by microorganism under anaerobic condition.Generally,it is influenced by microbial under waterlogging soil system.Therefore,study on characteristics of dissimilatory reduction of iron oxides in paddies and its influence factors,might help better understanding the paddies formation,its microbial ecology,also could help to elucidate the remediation and transformation of contamination in paddy soil.In this paper paddy soil samples were collected in china as experimental material. Co-culture incubation soil slurry anaerobic incubation and axenic culture methods were adopted in the experiment,to discuss effect of temperature on DIR process in paddy soil.The main results obtained are listed as followed:1.Under anaerobic constant temperature condition,DIR could obtain the maximum accumulation amount of Fe(Ⅱ) DIR process in four paddy soil treatments within the range of 10℃-25℃.Accumulation rate of Fe(Ⅱ) DIR increased as the temperature rising,meanwhile, the time of arriving at the highest accumulation rate decreased.Different paddy soil were variable with the range of 25℃-50℃,accumulation rate of Fe(Ⅱ) DIR increased as temperature rising in Tianjin and Jinlin paddy soi,however,accumulation rate of Fe(Ⅱ) DIR decreased as the temperature rising in Guangdong and Hunan paddy soil,which was because that microorganism biocoenosis in different district paddy soil were variable and temperature sensibility were variable.2.Under anaerobic constant temperature condition,accumulation rate of Fe(Ⅲ) DIR process increased as the temperature rising,meanwhile,the time of Fe(Ⅲ) DIR process decreased.The ratio of Fe(Ⅲ)/Fe(Ⅱ) could has a corelationship with Eh.The initial ratio of Fe(Ⅲ)/Fe(Ⅱ)DIR could has some corelationship with the PH and soil organic matter.The accumulation rate of ratio of Fe(Ⅲ)/Fe(Ⅱ) in DIR process was also stimulated as temperature rising,within the range of 10℃-25℃.The value of The ratio of Fe(Ⅲ)/Fe(Ⅱ) rise was not significant in four soil treatment DIR process.The constant rate of ratio of Fe(Ⅲ)/Fe(Ⅱ) could has a corelationship with rate of Fe(Ⅲ) DIR.3.Based on variable temperature culture experiment,the effect of temperature might be closely related to the mineralization of soil organic matter,which could provide a low molecular carbon source-facilitated the consumption by DIRB.Therefore,the maximum Fe(Ⅱ) accumulation amount might decreased under the higher temperature only when soil slurry incubation under constant temperature first,which might attribute to the depletion of soil organic matter which was facilitated to mineralization.4.Under the effect of Fe(Ⅲ) DIR capacity in paddy soil microorganism biocoenosis in different temperature treatment,Both accumulation amount and rate of Fe(Ⅱ) decreased as temperature rising.After 1 h 40℃treatment reaction of microorganism was higher than three other temperature treatments(70℃,60℃,50℃) significantly,accumulation amount of Fe(Ⅱ) with 70℃treatment was only 20%compared with 40℃treatment,considering microorganism biocoenosis in Jinlin paddy soil,accumulation amount of Fe(Ⅱ) with 70℃treatment decreased 81.75%compared with 40℃treatment.Meanwhile,accumulation amount of Fe(Ⅱ) with 70℃treatment decreased 81.83%and 74.77%compared with 40℃treatment in Tianjin and Hunan paddy soil.In conclusion,temperature had significant repression effect on DIR process.In addition,temperature treatment also had significant effect on the maximum accumulation rate and efficiency of Fe(Ⅱ)(Vmax),both decreased as temperature rising.5.In co-culture incubation treatment,AQDS was added under different temperature condition,it was shown that reduction rate of的Fe(OH)3 added AQDS treatment was significantly higher than CK,which confirmed that AQDS electron shuttles carrier could deliver electron which accelerated reduction of Fe(Ⅲ).JL paddy soil reduction rate was significantly higher than TJ SC paddy soil,which showed that different microorganism were variable among reduction capacities.In addition,microorganism in JL paddy soil was more sensitive in the reaction course,whose amount of Fe(Ⅱ) increased faster.As temperature rising from 30℃to 50℃,amount of Fe(Ⅱ) and reduction rate increased slightly in JL paddy soil microorganism biocoenosis,two others was not significantly.6.In axenic culture treatment,ferric(JX-a03,JX-a08,SC-aO4,SC-all) Fe(Ⅲ) reduction efficiency increased and the maximum Fe(Ⅱ) accumulation amount increased in different level as temperature rising from 40℃to 50℃,reduction rate and ferric JX-a03 the maximum Fe(Ⅱ) accumulation amount increased significantly,which showed that ferric JX-a03 could microorganism metabolize normally in 50℃,and physiological active also increased significantly,which could get the conclusion that ferric JX-a03 was thermophilic bacteria.
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