Evaluation of the potential horizontal gene transfer ability during chicken manure and pig manure composting

Resistance genes have been identified as emerging pollutants due to their ability to rapidly spread in the environment through horizontal gene transfer (HGT). Microbial community serves as the pivotal factor influencing the frequency of HGT during manure composting. However, the characteristics of HGT in microbial community from different types of manure were unclear. Therefore, this study aimed to evaluate the potential risk of HGT in bacterial community through the co-composting of chicken manure and pig manure in different proportions. The experimental results showed that the abundance of sulfonamide antibiotic resistance genes and integrase genes was higher during pig manure composting than those during chicken manure composting. In addition, the addition of pig manure also increased resistance genes abundance during chicken manure composting. These results suggested that the potential HGT risk was greater during pig manure composting. Furthermore, microbial analysis of co-composting suggested that bacterial community of pig manure was more competitive and adaptable than that of chicken manure. Ultimately, statistical analysis indicated that compared to chicken manure composting, the potential ability of HGT was greater during pig manure composting. This study provided the vital theoretical support and scientific guidance for mitigating the HGT risk during manure composting.