Diversity Of Plant Rhizosphere Bacteria And Ammonia Oxidizing Microorganism In Inner Mongolia Wetlands

The diversity of culturable bacteria of reed (Phragmites australis) rhizosphere fromnatural wetlands and degraded wetlands in Inner Mongolia Hetao irrigated region wasinvestigated in this study. The rhizosphere ammonia oxidizing bacteria (AOB) and ammoniaoxidizing archaea (AOA) community composition and dynamic changes of two plants, reedand cattail(Typha orientalis Presl), in constructed wetlands of the Inner Mongolia Hetaoirrigated region were examined by denaturing gradient gel electrophoresis (DGGE).A total of99bacterial strains with different colony characteristics were isolated on R2Amedium:45isolates from natural wetlands，44isolates from degraded wetlands. Bases on16SrRNA gene sequence analysis,45rhizosphere isolates from natural wetlands were groupedinto three groups, Proteobacteria (44.44%), Firmicutes (42.22%), and Actinobacteria(13.33%). The dominant group was Proteobacteria. The dominant genus was Bacillus(42.22%) and Pseudomonas (22.2%);44rhizosphere isolates from degraded wetlands werebelonged to three groups, Proteobacteria (20.45%), Firmicutes (47.73%), and Actinobacteria(31.82%). The dominant group was Firmicutes. And the genus Bacillus (40.91%) was thepredominant genus, which included18bacterial isolates. The results indicated that thediversity of rhizosphere bacteria from wetlands in Inner Mongolia Hetao irrigated region wasabundant and the rhizosphere bacterial communities between natural wetlands and degradedwetlands had differences.Diversity of gene amoA in rhizosphere AOB of the reed and cattail in the constructedwetlands was analyzed by using DGGE. Sequences of excised DGGE bands showed that themajor group was uncultured bacteria in rhizosphere AOB community, which similar to thegenera Nitrosomonas and Nitrosospira, and the dominat group was Betaproteobacteria. Basedon PCR-DGGE, distinct differences in AOB communities were revealed in relation tovegetation types, sampling time and types of soil. The results of variance analysis showed thatthe influence of vegetation types was extremely significant; the influence of differentsampling time was significant; the influence of soil types was not significant. This may be dueto different soil matrix in the constructed wetlands, but the physico-chemical characteristics of soil around the plant roots were similar. So the diversity index of AOB of the same plant inthe different sampling sites at the same sampling time had no evident difference.Diversity of gene amoA in rhizosphere AOA of the reed and cattail in the constructedwetlands was analyzed by using DGGE. Sequences of excised DGGE bands showed that themajor group was uncultured archaea in rhizosphere AOA community, and the dominat groupwas Crenarchaeota. Most of them are close to the soil AOA that had been studied, individualspecies belonged to AOA groups from the water environment and the Marine sediment. Theanalysis results of PCR-DGGE were consistent with the AOB analysis results, that distinctdifferences in AOA communities were mainly affected by vegetation types.