Structural and functional characteristics of microbial communities of typical coal gangue dumps in Guizhou Province

Abstract:

[Background] Coal gangue dumps stockpile coal wastes with low calorific values and heavy metals, which are generated during coal mining, along with a large amount of acidic wastewater and deteriorated eco-environment nearby. [Objective] This paper aims to explore the structure and functional characteristics of microbial communities in coal gangue dumps. [Methods] The soil samples of the dump surface and gangue layers, as well as the sediment samples from wastewater leaching outlets and dump downstream river, of a typical gangue dump in Liuzhi special district, Guizhou Province were collected. Metagenomics was employed to reveal the microbial community structures and functional characteristics of the samples. [Results] The results showed that bacteria were more diverse and abundant than archaea. The dominant bacterial phyla were Proteobacteria and Actinobacteria, and the dominant genera were Leptospirillum and Sulfobacillus. The dominant archaeal phyla were Candidatus_ Thermoplasmatota and Crenarchaeota, and the dominant genera were Thermoplasma and Metallosphaera. The dominant genera of bacteria and archaea in different sampling sites varied from each other, and Fe-oxidizing bacteria (FOB) and sulfur-oxidizing bacteria (SOB) were more abundant in the gangue layer soil and wastewater leaching outlet sediment than in the other two sampling sites. The genes for carbon, nitrogen, and sulfur metabolism were abundant in coal gangue, with six carbon fixation pathways, six nitrogen metabolism pathways, and three sulfur metabolism pathways detected. The dominant genes for carbon fixation were ACAT and E2.2.1.1, and the dominant pathway was reductive tricarboxylate cycle. For nitrogen metabolism, the dominant genes were nirB, nasA and narG, and the dominant pathway was denitrification. For sulphur metabolism, the dominant genes were cysH and sir, and the dominant pathway was assimilated sulphate reduction. [Conclusion] The findings are expected to enhance the understanding of mine ecology and provide a theoretical basis for the ecological restoration and pollution treatment in mining areas.