[Community Distribution of the Rhizospheric and Endophytic Bacteria of Phragmites australis and Their Limiting Factors in Iron Tailings].

The composition of the rhizospheric and endophytic bacteria Phragmites australis in spring and summer around the Qiananling iron tailings reservoir in the Huairou District of Beijing was studied using Illumina high-throughput sequencing technology. Sequencing identified 40 phyla, and Proteobateria and Actinobacteria were the dominant phyla in all samples, accounting for more than 80% of the sequences in all samples. At the genus level, Pseudoarthrobacter was dominant. α-diversity analysis showed that species richness(Sobs, Chao) and species diversity indexes(Shannon, PD) of the rhizosphere soil microorganisms were significantly higher than those of endophytes. The maximum and minimum differences of the Sobs, Chao, Shannon, PD indexes were 1336, 1582.24, 6.48, and 81.18, respectively. ß-diversity analysis indicated that there were significant differences in the community compositions of rhizosphere soil microorganisms and root endophytes, while now notable differences were observed between samples in different seasons. In addition, the dominant strains in each sample(such as Pseudomonas, Arthrobacter, and Streptomyces) were highly resistant to heavy metals. Among the 774 genera, a total of 250 genera coexisted in four types of samples, indicating that the microbial community composition of different samples had some degree of similarity. Correlation analysis between soil physical and chemical properties showed that Ni, Fe, available phosphorus, effective sulphur, and organic matter were significantly related to the microbial communities. Through the prediction of COG function, it was found that the microbial metabolic functions(i.e., energy production and conversion, amino acid transport and metabolism, carbohydrate transport and metabolism, inorganic ion transport, and metabolism) were abundant.

[Impact of Starvation Conditions on Biological Community Structure in Sulfur Autotrophic Denitrification Reactor].

Sulfur/dolomite and pyrite/dolomite autotrophic denitrification reactors were applied to treat the secondary effluent of wastewater treatment plant to explore the removal effect, the changes of microbial community, and recovery time of reactors after starvation period. It was shown in the results that after 30 d non-water starvation endurance, the effluent concentrations of NO3--N in sulfur/dolomite and pyrite/dolomite reactors increased from 1.78 mg·L-1, 11.32 mg·L-1 to 27.87 mg·L-1, 26.56 mg·L-1 respectively at the low temperature of 12-14℃. In addition, sulfur/dolomite and pyrite/dolomite reactors recovered within 5 d and 11 d since restarted and could maintain a good effect of nitrogen removal at low temperature. MiSeq high throughput sequencing results showed that the abundance and diversity of the bacterial communities in starvation period in both reactors were lower than those in recovery period. The dominating phylum was Proteobacteria in both reactors while the dominating class was ß-Proteobacteria. Thiobacillus was identified as the main genus for denitrification in sulfur/dolomite reactor.