The Analysis Of Community Structure Of Typical Disimilatory Iron-reducing Microorganism In Flooding Paddy Soil

As the earliest biological pathway of energy metabolism, Fe (III) reduction and relatedmicroorganism have been paid more and more attention for the ecological significance of itsown. Through non planting flooding paddy soil model, the dynamic characteristics ofcommunity structure of Clostridium, Bacillus and Geobacteraceae in Jilin, Tianjin, Jiangxiand Ningxia paddy soils was researched. By16S rRNA-PCR-DGGE technology, the changesof community structure of Clostridium, Bacillus and Geobacteraceae were analysed atflooding time0d,1d,5d,10d,20d,30d,40d and60d. Based on the sequence of DGGEpredominant bands, the phylogenetic tree was constructed. The main findings are as follows:1. The DGGE atlas and α diversity indexes were showing that community structure ofClostridium, Bacillus and Geobacteraceae in different paddy soil existed dynamic successionobviously in the flooding incubation.(1)In the process of flooding incubation, diversity of Clostridium changed: In the4paddy soils, the diversity indexes were decreased significantly at the early stage then went upslowly until60d. In the Jilin and Jiangxi paddy soil, the valley value was between1-5d, and itis much closer to1d in Tianjin and Ningxia soil.(2) In the process of flooding incubation, diversity of Bacillus changed: In Jilin andTianjin paddy soil, the diversity indexes rose rapidly from0d to1d, significantly decreased at5d, then fluctuated at later stage. In Jiangxi paddy soil it reached the peak at30d, declinedslowly to60d; and it peaked at5d and remained stable until60d in Ningxia paddy soil.(3) In the process of flooding incubation, diversity of Geobacteraceae changed: thediversity indexes showed increase trend from0d to1d in4paddy soil. It basicly kept stable to60d in Jilin and Jiangxi paddy soil. And the diversity indexes emerged a significant drop after1d in Tianjin and Ningxia paddy soil. In Tianjin paddy soil the Valley value appeared at5d,and Peak value appeared at20d, then the diversity indexes remained nearly unchanged. InNingxia paddy soil the diversity indexes was down after1d, and reached Valley value in20d,then kept stable to60d.2. PCA of community structure based on the predominant bands sequence and DGGEgray value.(1) PCA of Clostridium: treatments5d to40d of Jilin paddy soil were together, showedthat community structure was similar at the middle stage. In Tianjin and Jiangxi paddy soilcluster was decentralized, showing that the community structure existed fluctuation in the process of incubation. In Ningxia paddy soil, treatments10d to60d were loose together,indicating that the community structure was tend to be stable after10d.(2) PCA of Bacillus: treatments10d to60d were together in4paddy soils, showing thatBacillus community changed in the initial cultivation, and it tended to be stable after10d.(3) PCA of Geobacteraceae: treatments10d and60d were together in Jilin and Jiangxipaddy soil, treatments were edcentrailzed in Tianjin paddy soil, and treatments5d to60d weretogether except40d in Ningxia paddy soil, showing that community in Jilin and Jiangxi paddysoil was trend to be stable after10d. Community structure in Tianjin paddy soil did not reacha stable state in later culture.3． The phylogenetic trees based on DGGE dominant bands sequence were showing thatmicrobial community structure of Clostridium, Bacillus and Geobacteraceae were not onlydifferent, but also had in common in different flooding paddy soils.(1) the Clostridium DGGE dominant bands in Tianjin and Jiangxi paddy soil wereassociated with Clostridium microorganisms; in the Jilin and Ningxia paddy soil DGGEdominant bands were clustered into two clusters, and most of them were clustered withClostridium organisms, a sequence in Jilin paddy soil was clustered with unclassified16SrRNA sequence in the island of Madagascar bauxite samples, in Ningxia paddy soil therewere some sequences getting with Uncultured bacterium clone UA68together.(2) Bacillus DGGE dominant bands were clustered into two clusters in4paddy soils, thedominant clusters were clustered with Bacillus into one group; another cluster in Jilin paddysoil were clustered with Bacterium STV2into one group, in Tianjin paddy soil clustered withSphingomonas sp. Es14into one group, in Jiangxi paddy soil clustered with unculturedbacterium clone D13into one group, and in Ningxia paddy soil clustered with Bacterium KR1991/1119together.(3) Geobacteraceae DGGE predominant bands in4paddy soils were clustered into twoclusters, the majority of cluster were clustered with Geobacteraceae into one group; andanother cluster of bands in Jilin paddy soil were clustered with Cystobacter sp. xj65together,in Tianjin paddy soil clustered with Corallococcus exiguous strain HBUM94201into onegroup, in Jiangxi paddy soil clustered with Cystobacter sp. into one group, Ningxia paddy soilclustered with Uncultured delta photobacterium clone MP-R108.Through this study, the community distribution structure and dynamic characteristics ofsuccession process of3kinds of typical Fe (III) reduction in different paddy soils wereascertained in flooding incubation, theoretical basis of relationship between Fe (Ⅲ) reductionand community structure and the difference of microbial Fe (Ⅲ) reduction capability indifferent paddy soils was provided.