Biochar Reduced\nthe Risks of Human Bacterial Pathogens\nin Soil via Disturbing Quorum Sensing Mediated by Persistent Free\nRadicals

Biochar has great potential in reducing the abundance\nof antibiotic\nresistance genes (ARGs) and mobile genetic elements (MGEs) from soil.\nHowever, its efficiency in removing other biological pollutants, such\nas human bacterial pathogens (HBPs) and virulence factor genes (VFGs),\nis rarely studied. Herein, by pyrolyzing rice straw (RS) and pine\nwood (PW) at 350 and 700 °C, we prepared a series of biochar\n(RS350, RS700, PW350, and PW700) and investigated their impacts on\nthe abundance and pathogenicity of HBPs. Compared with PW biochar,\nRS biochar effectively reduced the abundance of HBPs by 6.3–40.1%,\nas well as their pathogenicity, evidenced by an 8.2–10.1% reduction\nin the abundance of VFGs. Mechanistically, more persistent free radicals\n(PFRs) were formed in RS biochar than that of PW biochar during pyrolysis,\nand PFRs triggered the degradation of <i>N</i>-butyryl-l-homoserine lactone (C4-HSL) from 1.05 to 0.68 ng/kg, thereby\ndisturbing the quorum sensing (QS) of HBPs. Once the QS was disturbed,\nthe communications among HBPs were hindered, and their virulence factors\nwere reduced, which ultimately lowered the abundance and pathogenicity\nof HBPs. Collectively, our study provides insights into the role of\nbiochar in decreasing the risks of HBPs, which is significant in the\ndevelopment of biochar-based technologies for soil remediation.