The spatial distribution of heavy metal contamination, microbial communities, and resistance genes in agricultural soil near a manganese mine in China

The large-scale manganese mining causes severe heavy metal contamination, posing a significant potential risk to human health. Songtao County is one of the most important manganese mining areas in China, where the disorderly mining and extensive production has inevitably caused serious pollution. However, it's still unclear how Mn production activities affect agricultural soils located relatively far from the mining sites. Therefore, we investigated the horizontal and vertical distribution of heavy metal contamination, microbial communities, and resistance genes in the agricultural soils located at Songtao County. Metagenomic sequencing revealed that Proteobacteria, Acidobacteria, Rokubacteria, Chloroflexi, and Actinobacteria were the most abundant phyla. The diversity and composition of the bacterial communities varied significantly between different sampling sites and depths. Redundancy and Spearman correlation analysis indicated that total nitrogen, total organic carbon, total K, and Mn were the primary environmental factors determining the distribution of bacterial communities. The bacterial communities in Wuluo were influenced by Hg, Zn, Cu, Ni, and As, whereas in Mushu, it was primarily affected by Mn levels. A large account of heavy metal resistance genes, manganese resistance genes, and antibiotics resistance genes were identified. The relative abundances and correlation analysis of these resistance genes exhibited observed correlations based on the potential co-selection mechanisms, suggesting that Mn and heavy metals, as well as antibiotics, might shape the microbiome and resistome in this agricultural soil. These findings provide an insight for the surveillance, maintenance, and remediation of the agricultural soil and offer theoretical evidence for improving the agricultural soil environment.