Reduction of mobile genetic elements determines the removal of antibiotic resistance genes during pig manure composting after thermal pretreatment.

Animal manure is a primary repository of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs). This work explored the efficiency of ARGs and MGEs removal during pig manure composting after thermal pretreatment (TPC) and the underlying mechanisms. TPC resulted in a decrease of 94.7% and 92.3% in the relative abundance of ARGs and MGEs which was 48.9% and 76.6% lower than control, respectively. Network analysis indicated that reductions of ARGs and MGEs in TPC were relevant to decrease in the amount and abundance of bacterial hosts. Furthermore, total ARGs abundance in TPC was correlated with that of intI1 and Tn916/1545 (P < 0.001). Redundancy analysis supported a leading role of MGEs in ARGs dynamics in TPC. Reduction of MGEs rather than bacterial hosts contributed mainly to ARGs removal in TPC, as revealed by structural equation modeling. In conclusion, TPC was an effective method to treat animal manure containing ARGs.

Effects of two-stage microbial inoculation on organic carbon turnover and fungal community succession during co-composting of cattle manure and rice straw.

This study explored the effects of single-stage inoculation (SSI) versus two-stage inoculation (TSI) on organic carbon components, product quality and fungal community during co-composting of cattle manure and rice straw. Both inoculation methods accelerated the temperature increase and elevated the composting temperature. TSI resulted in a second fermentation stage and extended the thermophilic stage from 22 to 29 days. Compared with SSI, TSI promoted the degradation degree of cellulose, hemicellulose and lignin by 25.9%, 16.5% and 47.4%, and increased the content of total nutrients and humus carbon by 5.9% and 10.5% in final products, respectively. TSI significantly increased the relative abundance of Aspergillus, Trichoderma, Neurospora, Mycothermus, Malbranchea and Gloeophyllum in the second fermentation stage. Spearman correlation analysis indicated that Aspergillus, Neurospora, Trichoderma and Gloeophyllum were the key fungi for lignocellulose degradation and humification. Redundancy analysis showed that temperature was the major environmental factor affecting fungal community succession in TSI.