Abstract
More than twenty abandoned coal mines in the Yudong River Basin of Guizhou Province have discharged acid mine drainage (AMD) for a long time. The revelation of microbial community composition, interaction patterns, and metabolic functions can contribute to abetter understanding ofsuch ecosystems, which in its turn can be helpfulin the development of strategies aiming atthe ecological remediation of AMD pollution. In this study, reference and contaminated soil samples were collected along the AMD flow path for high-throughput sequencing. Results showed that the long-term AMD pollution promoted the evolution of γ-Proteobacteria, and the acidophilic iron-oxidizing bacteria Ferrovum (relative abundance of 15.50%) and iron-reducing bacteria Metallibacterium (9.87%) belonging to this class became the dominant genera. Co-occurrence analysis revealed that the proportion of positive correlations among bacteria increased from 51.02 (reference soil) to 75.16% (contaminated soil), suggesting that acidic pollution promotes the formation of mutualistic interaction networks of microorganisms. Metabolic function prediction (Tax4Fun) revealed that AMD contamination enhanced microbial functions such as translation, repair, and biosynthesis of peptidoglycan and lipopolysaccharide, etc., which may be an adaptive mechanism for microbial survival in extremely acidic environment. In addition, acidic pollution promoted the high expression of nitrogen-fixing genes in soil, and the discovery of autotrophic nitrogen-fixing bacteria such as Ferrovum highlights the possibility of using this taxon for bioremediation of AMD pollution.
Highlights
The total number of coal mines in China has been decreased from more than 80,000 (Feng et al 2016; Xu et al 2016) to around 4,700 under the guidance of a series of national policies
Metabolic function prediction (Tax4Fun) revealed that acid mine drainage (AMD) contamination enhanced the microbial functions such as translation, repair, and biosynthesis of peptidoglycan and lipopolysaccharide etc., which may be an adaptive mechanism for microbial survival in extremely acidic environment
We found that the long-term AMD pollution significantly affected the microbial community structure, interaction patterns and metabolic functions of soil microorganisms, mainly included: (1) The AMD contamination inhibited the survival of Chloroflexi, Acidobacteriota, Actinobacteriota etc. of soil, significantly reducing the richness and diversity of soil microorganisms while promoting the evolution of γProteobacteria
Summary
The total number of coal mines in China has been decreased from more than 80,000 (Feng et al 2016; Xu et al 2016) to around 4,700 (by the end of 2020) under the guidance of a series of national policies. Large amounts of groundwater rebound after coal mine abandonment, making the mining area a collection of contaminants (Chen et al 2019). For high sulfur abandoned coal mines, associated FeS2 in coal seams and gangue was oxidized by microbial catalysis, producing large amounts of acid mine drainage (AMD) (Sharma et al 2020). If not treated properly, AMD can contaminate soil, groundwater and surface water, etc., posing a major threat to humans and the environment (Jin et al 2020; Rambabu et al 2020). Due to the lack of effective management measures, AMD from abandoned coal mines was usually discharged directly into the environment without any treatment, posing a higher ecological risk compared to producing mines. China currently has a large number of abandoned coal mines, and the associated safety and environmental problems need more attention
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