Comprehensive effects of tea branch biochar on antibiotic resistance profiles and C/N/S cycling in the compost microbiota of animal manure

The comprehensive effects of exogenous additives on microbial-driven antibiotic resistance profiles and C/N/S conversion in animal manure composting remains uncertain. This study examined whether tea branch biochar could regulate the microflora involved in antibiotic resistance and C/N/S conversion during pig and chicken manure composting. Compared with the control treatment, biochar addition prolonged the high-temperature period (>55 °C) for 1-2 days and raised the maximum temperature in chicken manure composting. Moreover, biochar addition reduced the prevalence of antibiotic resistance genes (ARGs) in both pig and chicken manure composting by up to 30 %, targeting various types of ARGs such as peptide, phenicol, and diaminopyrimidines. Additionally, the compost microbiota exhibited the overlaps of C/N/S conversion functions. Luteimonas (Xanthomonadaceae) was identified as a dominant bacterium responsible for C/N/S conversion in both pig and chicken manure composting, while also acting as a potential ARG carrier. Thus, Luteimonas is crucial in shaping antibiotic resistance profiles and C/N/S cycling in animal manure composting, indicating its role as a keystone genus. These findings suggest that tea branch biochar can mitigate the spread of ARGs from animal manure, as well as enhance nutrient cycling and compost quality.