Microorganisms inhabiting mine tailings require specific metabolic strategies to survive, which may hold potential for pollution clean up. Effective in situ bioremediation will rely on an in-depth understanding of the function of the bacterial communities, especially the abundant and metabolically active phylotypes. In this study, the bacterial communities collected from an alkaline tailing site were profiled by 16S rRNA gene amplicon sequencing as well as shotgun metagenomic analysis. Our results indicated that potentials for carbon and nitrogen fixation as well as metal resistance and transformation were widespread among the bacterial community members, especially in highly enriched phylotypes, such as members of Thiobacillus and Meiothermus. Important functional microbial guilds including carbon and nitrogen fixers may contribute to phytoremediation by providing nutrients for hyperaccumulator plants. In addition, metal-metabolizing bacteria may influence metal speciation and solubility. This discovery provides an understanding for microbial survival strategies in the tailings and lays the foundation for future potential manipulation of the tailing microbiome for in situ bioremediation.

Five rice paddy soils located in southwest China were selected for geochemical and microbial community analysis. These rice fields were irrigated with river water which was contaminated by Fe-S-rich acid mine drainage. Microbial communities were characterized by high-throughput sequencing, which showed 39 different phyla/groups in these samples. Among these phyla/groups, Proteobacteria was the most abundant phylum in all samples. Chloroflexi, Acidobacteria, Nitrospirae, and Bacteroidetes exhibited higher relative abundances than other phyla. A number of rare and candidate phyla were also detected. Moreover, canonical correspondence analysis suggested that pH, sulfate, and nitrate were significant factors that shaped the microbial community structure. In addition, a wide diversity of Fe- and S-related bacteria, such as GOUTA19, Shewanella, Geobacter, Desulfobacca, Thiobacillus, Desulfobacterium, and Anaeromyxobacter, might be responsible for biogeochemical Fe and S cycles in the tested rice paddy soils. Among the dominant genera, GOUTA19 and Shewanella were seldom detected in rice paddy soils.

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