Enrichment and response of iron-metabolizing microorganisms and metabolic genes in the contaminated area of stratified stacking coal gangue dumps, Northern China.

ABSTRACT

In the Xishan coalfield of northern China, the stratified stacking of soil and gangue was applied to limit the acid pollution from high-sulfur coal gangue. In this study, we found that stratified stacking can effectively neutralize the acidity, with the pH value of gangue-leaching water being 6.02-8.13. In contrast to the acidic contaminated area, most of the microorganisms in the study area sediment were neutrophilic, with the main genera being Arthrobacter, Pseudorhodobacter, Pseudomonas, and Rhodoferax. A variety of iron- and sulfur-metabolizing bacteria was discovered in the gangue-leaching sediment, with the total relative abundance ranging from 4.20 to 23.75%, of which the iron-reducing bacteria (FeRB) accounted for the highest percentage. The distributions of these functional microorganisms in the samples were significantly influenced by Fe and S. The co-occurrence network analysis revealed a significant positive correlation between the iron- and sulfur-metabolizing bacteria in the sediment (93.75%), indicating a strong reciprocal symbiotic relationship between these bacteria. The iron and sulfur metabolism genes in the sediment were predicted and compared based on the Tax4Fun functional prediction method. Results showed that functional genes related to iron metabolism were highly expressed in the gangue-leaching sediment. This study enhances the understanding of iron and sulfur metabolism in gangue-leaching contaminated areas.