| Geobacteraceae is an important dissimilatory Fe(Ⅲ) reducer, widely distributing in a diversity of sedimentary in which Fe(Ⅲ) reduction is important, such as aquatic sediments, subsurface sediments contaminated with organic and/or metal contaminants. It play an important role in bioremediation. The periodic change of oxidation and reduction status paddy influence the community structure of dissimilatory Fe(Ⅲ) reducer significantly in paddy soil.The dynamic characteristics of community structure and relative abundance of Geobacteraceae were investigated in order to understand their response to microbial iron(Ⅲ) reducing by simulate the flooded paddy soil. HZ and ZJ paddy soil was incubated anaerobically for 1 h, 1 d, 5 d, 10 d, 20 d and 30 d and the amount of Fe(Ⅱ) was determined during the flooding incubation respectively and Logistic equation wsa used to fit this data. Total DNA was extracted from all treated samples and PCR was performed to amplify the geobactercaeae 16S rDNA using Specificity general primer. Clone library of 12 samples was constructed. The diversity and communtiy structure were analysised using RFLP method, and reletive abundance of geobacteraceae were determined by real-time PCR. We retrieved partial RFLP preponderant type Geobacteraceae 16S rDNA sequences which was used to construct phylogenetic tree.This study obtain the main results as follows:(1) Microbial reduction of iron(Ⅲ) changed greatly in early time and was stable after incubated for 20 d in HZ paddy soil and the largest iron reduction potential was 10.16 mg/g with a Vmax of 1.064 mg/(g.d) at the time of 4.84 d whereas this process achieved plateau after 20 days flooding, while in ZJ paddy soil iron(Ⅲ) reduction potential was was 8.27 mg/g and the Vmax was 1.341 mg/(g.d) at the time of 3.36 d and achieved plateau after 15 days flooding(2) We acquired 64/155, 64/154, 76/162, 62/152, 85/155 and 54/154 RFLP types from clone library in HZ paddy soil treated 1 h to 30 d, and the coverage value was from 61.29% to 81.82%. In ZJ paddy 71/149,74/139,75/153,72/150,73/151 and 61/153 RFLP types was obtained and the coverage value was from 64.75% to 73.86%。(3) Diversity of Geobacteraceae in HZ paddy soil, given by alpha indices, fluctuated during the flooding incubation. Two peaks of diversity were observed in treatments of 5 d and 20 d respectively, while significant low diversity appeared in samples of 10 d and 30 d. In ZJ paddy soil,αindices showed that the diversity of Geobacteraceae decreased gradually during flooding incubation, highest in 1 d and lowest in 30 d. Beta indices described the differences community structures of Geobacteraceae between different treatments and hence reflected the variation of the flooding situation over time in two soil.(4) In samples of HZ paddy soil, 10 RFLP-based preponderant types were found, which fell into clade 1 and clade 2 of Geobacteraceae, while in ZJ paddy soil, we also botained 10 preponderant RFLP types distribute in 3 clade. Most of this preponderant RFLP in 2 paddy soil are, however, far away from the reference Geobacteraceae sequence which come from Freshwater sediments and Contaminated aquatic sediments in phylogenetic tree.(5) The relative abundance of Geobacteraceae was the lowest in sample 1 d (1.20%) and the highest in sample 20 d (4.54%) in HZ paddy soil, while in ZJ paddy soil, the lowest (0.413%) and the highest (4.111%) appear in 1 d and 10 d respectively. We can conclude according to the above results that the dynamic variation of Geobacteraceae diversity, community structure and abundance are closely related to microbial iron(Ⅲ) reducing in flooding paddy soil. |
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