Heavy metal pollution pressure in gold mines shows overall suppressed biochemical sulfur cycle

Abstract

Sulfur cycle is an important material cycle in soil, and soil sulfur-metabolizing microorganisms are one of its prominent drivers. However, the fate of the sulfur cycle under the stressful condition of soil heavy metal pollution due to mining is unknown. In this study, three representative areas with low (L), medium (M) and high (H) levels of heavy metal pollution were selected to investigate the effects of heavy metal contamination levels on sulfur metabolizing microorganisms, sulfur cycling pathways and sulfur cycling genes by using metagenome sequencing and SCycDB sulfur cycle database annotation. The results showed that the relative abundance of sulfur cycle genes in the L, M, and H regions was 6.45 ± 0.12, 6.29 ± 0.15, and 5.75 ± 0.21, respectively; the abundance of sulfur cycle genes showed a decreasing trend with the increase of heavy metal pollution, and the sulfur cycle pathways and microbial sulfur metabolism were inhibited, and the dominant bacteria of the sulfur metabolizing bacterial community evolved gradually from Actinobacteria to Proteobacteria with abundances changing from 0.38 to 0.22 to 0.29 and 0.30, respectively; the proportion of sulfur cycle genes of different types in the sulfur metabolizing metabolizers did not vary with heavy metal pollution, indicating that different sulfur cycling genes in sulfur metabolizers show a uniform decline with increasing heavy metal pollution; dmsA may be a key gene mediating the adaptation and remediation of sulfur metabolizing bacteria to heavy metal pollution. The results reveal the effects of heavy metal pollution in mining areas on the sulfur cycle and provide new insights into the mechanisms of adaptation and remediation of heavy metal pollution by sulfur metabolizing microorganisms.