Biochar promotes removal of intracellular and extracellular antibiotic resistance genes in sludge compost: Reshaping microbial communities
Xinxin Wu, Zhurui Tang, Yuqian Li, Zhe Du, Wei Li, Simiao Wang, Caihong Huang
Abstract
Antibiotic resistance genes (ARGs), as emerging pollutants, jeopardize ecological and public health. Extracellular ARGs (eARGs) pose heightened risks due to their mobility, accelerating resistance spread. However, studying eARGs remains challenging given extracellular DNA's environmental instability. While aerobic composting of sewage sludge reduces ARGs, resurgence of certain genes (e.g., sulfonamide resistance) in later stages may exacerbate resistance risks. This study investigated the effects of sludge-derived biochar and commercial biochar on the reduction of intracellular and extracellular sulfonamide ARGs during sludge composting. After the addition of both biochars, intracellular ARGs (iARGs) gradually decreased as composting progressed, while eARGs initially increased before subsequently declining. The biochars reshaped the microbial community in sludge composting, significantly increasing the number of differentially enriched microbial species, altering community assembly processes, and reducing bacterial diversity and richness-key factors in ARGs reduction. The addition of both biochars also decreased the abundance of intl1, and combined with the inactivation of certain microorganisms and disruption of cell membranes, effectively suppressed the horizontal gene transfer (HGT) of eARGs. However, compared to commercial biochar, the application of sludge-derived biochar led to an increase in potential host microorganisms for ARGs, highlighting a potential risk associated with the production of biochar from sludge. Additionally, the biochars modified environmental factors such as moisture and organic content, further enhancing eARG removal. This study proposes a "waste-to-waste" circular economy model. By reusing sludge-derived biochar in composting, it not only suppresses the spread of ARGs but also achieves high-value utilization of sludge, enabling synergistic pollution control.