Effect Of Phosphate On Abundance And Community Structre Of Disimilatory Iron-reducing In Paddy Soil

A wide variety of microorganisms in soil, involved in many biochemical metabolicprocesses, play an important role on the growth of crops. In the anaerobic environment offlooded paddy soil, dissimilatory iron-reducing microorganism become a hot topic ofscientific research. Geobacteraceae and Anaeromyxobacter represent the kind ofsingle-minded dissimilatory iron-reducing microorganism and Clostridium and Bacillus onbehalf of the other kind, which grow with iron-reducing processes. Every kind ofiron-reducing microorganisms have important ecological significance for they have manypractical value. Such as inhibition of CH4, degradation of organic pollutants, detoxification ofradioactive substances and heavy metals in soils, and development of microbial cell. Thestudies of recent years shows that phosphate has a certain influence on the reduction processof iron-reducing. However, there are no studies about if phosphate makes an import role ofthe growth of dissimilatory iron-reducing microorganism.The dynamic characteristics of relative abundance and community structure of thetypical dissimilatory iron-reducing microorganism were investigated by Real-Time PCR andDGGE in order to understand if they were affected by high concentration phosphate in theflooded paddy soil. The results will provide impotant theoretical foundation for the studies ofphysiological and biochemical fuction of the dissimilatory iron-reducing microorganism.The main results of this study were as follows:（1） It shows that the abundance of four typical dissimilatory iron-reducingmicroorganism generally have increased dramatically and is higher than that of P1and P2treatments. The index of Fe(II) concentration is at the rising stage in5d, and the dissimilatoryiron-reduction reaction rate is higher and the reaction rate is CK>P1>P2at the moment. Itpresents positively correlated to the abundance increase of dissimilatory iron-reducingmicroorganism. In CK treatments, they show that the rise of abundance of alienation of ironreducing microorganism promote the alienation of iron reduction reaction. The addition ofphosphate treatments reduce the abundance of dissimilatory iron-reducing microorganism,which lead to a decline of the reaction rate.（2）The abundance of Clostridium and Bacillus under the different treatments in the early stage (1-5d) of the flooded treatments is the highest for the entire process of floodedtreatments. However, the abundance of Geobacteraceae and Anaeromyxobacter is the highestin30d in the absence of iron treatment, while it is20d for adding iron oxide. A tentativeinference is that Clostridium and Bacillus play the leading role on the process of dissimilatoryreduction in the initial flooding time. However, it turns into Geobacteraceae andAnaeromyxobacter in the late flooding time.（3）Comparing DGGE profiles of Geobacteraceae and Clostridium in CK or P2treatments, the DGGE of Geobacteraceae mostly belong to conservative stripe, appearedcontinuously in all the two treatments. But no bands were only appeared in CK or P2, just afew bands existed differences of gray level. Therefore the high concentration of phosphate issupposed no significant impact on the community structure of Geobacteraceae. As toClostridium, bands of3,4,5,6,8only appeared in the specific treatments, bands of11,12,13,14also have obvious difference of gray level in CK and P2treatments. So high concentration ofphosphate is supposed to impact significantly on the community structure of Clostridium.From DGGE profiles of P1and Fe+P1treatments, Geobacteraceae’s bands of3,9,18,20,21,22have difference of gray level in different periods of flooding treatments. Clostridium bandsof3,4are different obviously in the two treatments; from DGGE profiles of P2and Fe+P2treatments, Geobacteraceae’s bands of11,12,13,18,19,20have obvious difference, andClostridium’s bands7,8,11,22also have obvious difference. So we could suppose thatincrease of the electron acceptor, by addition of iron oxide, promote the community structurechange of dissimilatory Fe(III)-reducing microorganisms.（4）As to the PCA analysis of Geobacteraceae by UniFrac, the community structure ofGeobacteraceae in CK and P2treatments are similar in20-30d and there are largedifferences in1d and40d; the community structure of Geobacteraceae in P2and Fe+P2treatments are different especially in1d and5d and similar in10-40d. Therefore we couldsuppose that as to the flooded incubation time, the high concentration of phosphate is moreeffective to the community structure of Geobacteraceae in initial stage of flooded treatmentthan the later stage. As to the PCA analysis of Clostridium by UniFrac, the communitystructure of Clostridium in CK and P2treatments are different greatly in1d; and thecommunity structure of Clostridium in P2and Fe+P2have more difference in1-5d and30-40d. So the impact of the high concentration of phosphate to the community structure ofClostridium emerge mainly in the initial stage and the later stage of the flooded treatments.（5）Steadily appearing in the whole stage of the flooded treatment and with highabundance, Geobacter bemidjiensis、Geobacter bremensis、Geoalkalibacter subterraneus、 Clostridium disporicum、Clostridium mesophilum、Clostridium stercorarium are the dominantbacteria in the flooded paddy soil. Therefore, the contribution of them to the dissimilatoryiron-reducing process is the largest. In addition, Clostridium caminithermale、Clostridiumnitrophenolicum Geobacillus lituanicus、 Geobacillus thermoleovorans、 Geoalkalibactersubterraneus、contributed greatly to the dissimlatory iron-reducing process in the earlyflooded treatment and Geoalkalibacter subterraneus contribute conversely. Geobactertoluenoxydans、 Geobacter bemidjiensis、 Geobacillus thermoleovorans、 Geobacilluslituanicus、 Thermobrachium celere、 Flavonifractor plautti(Clostridium orbiscindens)、Clostridium psychrophilum、Clostridium stercorarium and Clostridium alkalicellum havehigher tolerance to phosphate, but Geoalkalibacter subterraneus is lower of the resistance tophosphate.