The Community Structure Of Iron-Reducing Geobacteraceae In Rice Rhizosphere Under The Stress Of Polycyclic Aromatic Hydrocarbons

Geobacteraceae is a dominant bacterium in the different contaminanted sites. As far as we know, few studies on the relationship between the degradation of PAHs and Geobacteraceae in paddy soils have been conducted. The spatial-temporal changes in community composition of iron-reducing Geobacteraceae were studied in the rice rhizosphereunder the pollution of polycyclic aromatic hydrocarbons (PAHs). These spatial-temporal changes were investigated by using the techniques of Geobacteraceae-specific polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE). The effect of rhizoshpere (including different disitance from the root surface), PAHs concentration and pollution time on the community of iron-reducing Geobacteraceae was studied. Main results are as follows:1. The abundance and diversity of iron-reducing Geobacteraceae in the rice rhizosphere soil with the pollution of polycyclic aromatic hydrocarbons (PAHs) were greater than those in the bulk soil at the initial 30 days after rice transplanting. However, no significant difference was found in the community structure of iron-reducing Geobacteraceae at the different distances from root surface with and without PAHs treatments at the 45 days after rice transplanting.2. The abundance and diversity of iron-reducing Geobacteraceae were siginificant higher in the rice rhizosphere soils with the pollution of PAHs as compared to the control soil wthout PAHs treatment at the initial 30 days after rice transplantation. There were difference in the community structure of iron-reducing Geobacteraceae at the different concentrations of PAHs in the rice rhizosphere soils at the 45 days after rice transplanting. However, no differences were obtained in the community composition of iron-reducing Geobacteraceae in the bulk soils at different concentrations of PAHs at the 45 days after rice transplanting.3. The community composition of iron-reducing Geobacteraceae in the rhizoshperic soil was more siginificantly changed at different sampling time in the PAHs treated soils as compared to the control soil without PAHs addition. The effect of PAHs on the abundance and diversity of iron-reducing Geobacteraceae in the rhizoshperic soil were decreased with time. In both rhizospheric soils without PAHs addition and PAHs-treated soils without rice growth, no change was found in the iron-reducing Geobacteraceae community with the sampling time. It is suggested that the iron-reducing Geobacteraceae in rice rhizosphere with the pollution of PAHs may play an important role in the degradation of PAHs.4. Several bands were predominated in the rice rhizosphere soil treated with PAHs, which were band 16,19,23, and 26. The bands 16 and 23 just had 96% similarity with Geobacer uraniireducens Rf4, while the band 19 and 26 were identified as Geobacer bremensis strain Dfrl with 98% and 95% similarity, respectively,...