Metagenomic Analysis Revealed the Changes in Antibiotic Resistance Genes and Heavy Metal Resistance Genes in Phosphate Tailings Compost

Phosphate tailings are usually rich in phosphorus and some other mineral nutrients, which is very suitable for composting. In this study, 60 days of composting using phosphate tailings, chicken manure, and straw resulted in a significant decrease in total nitrogen (TN) content from 1.75 ± 0.12 g/kg to 0.98 ± 0.23 g/kg (p < 0.01), with a nitrogen retention of 56%, an increase in water-soluble phosphorus (Ws-P) from 3.24 ± 0.14 mg/kg to 7.21 ± 0.09 mg/kg, and an increase in immediate potassium (AK) from 0.56 ± 0.21 mg/kg to 1.90 ± 0.11 mg/kg (p < 0.05). Metagenomic sequencing showed little changes in the diversity and abundance of microbial communities before and after composting, but changes in species composition and the abundance of archaea, bacteria, and fungi resulted in differences in community structure before and after composting. Composting contributed to a lower gene abundance of ARGs and MRGs. The addition of phosphate tailings combined the functions of chemical regulation and nutrient enrichment, and its synergistic effect significantly optimized the nutrient cycling in the composting system.