Department of Environmental Science, Zhejiang University, Hangzhou 310058, China.
Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Hangzhou 310058, China.
Environ Sci Technol. 2022 Sep 6;56(17):12573-12583. doi: 10.1021/acs.est.2c02701. Epub 2022 Aug 9.
Horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs) through plasmid-mediated conjugation poses a major threat to global public health. Biochar, a widely used environmental remediation material, has remarkable impacts on the fate of ARGs. However, although biochar was reported being able to inhibit the HGT of ARGs via conjugation and transformation, little is known about the intracellular process that mediates the inhibition effects. On the other hand, as typical natural organic matter, fulvic acid is a common environmental influencer, and how it interferes with the effect of biochar on the HGT of ARGs is unknown. Therefore, this study investigated the effects on the conjugative transfer of ARGs between MG1655 and HB101 carrying plasmid RP4, with biochars pyrolyzed at three temperatures and with the corresponding biochars coating with fulvic acid. Results showed that biochar with higher pyrolyzed temperature had a more substantial inhibitory effect on the conjugative transfer of the RP4 plasmid. The inhibitory effect of biochar was mainly attributed to (i) down-regulation of plasmid transfer gene expression, including the formation of conjugative transfer channel and plasmid replication, due to restrained adenosine triphosphate (ATP) energy supply and (ii) decreased cell membrane permeability. Conversely, the fulvic acid coating diminished this inhibition effect of biochar, mainly by providing more ATP and strengthening intracellular reactive oxygen species (ROS) defense. Our findings shed light on the intracellular process that mediates the effects of biochar on the conjugative transfer of ARGs, which would provide support for using biochar to reduce the spread of ARGs.
水平基因转移（HGT）通过质粒介导的共轭作用转移抗生素耐药基因（ARGs）对全球公共健康构成重大威胁。生物炭作为一种广泛使用的环境修复材料，对 ARGs 的命运有显著影响。然而，尽管已经报道生物炭能够通过共轭和转化抑制 ARGs 的 HGT，但介导抑制作用的细胞内过程知之甚少。另一方面，作为典型的天然有机物，腐殖酸是一种常见的环境影响因素，其如何干扰生物炭对 ARGs 水平基因转移的影响尚不清楚。因此，本研究调查了三种不同热解温度的生物炭及其相应的腐殖酸涂层对 MG1655 和携带质粒 RP4 的 HB101 之间 ARGs 共轭转移的影响。结果表明，热解温度较高的生物炭对 RP4 质粒的共轭转移有更强的抑制作用。生物炭的抑制作用主要归因于（i）由于三磷酸腺苷（ATP）能量供应受限，抑制了质粒转移基因的表达，包括共轭转移通道的形成和质粒复制，以及（ii）降低了细胞膜通透性。相反，腐殖酸涂层减弱了生物炭的这种抑制作用，主要是通过提供更多的 ATP 和增强细胞内活性氧（ROS）防御。我们的研究结果揭示了生物炭对 ARGs 共轭转移的影响的细胞内过程，这将为利用生物炭减少 ARGs 的传播提供支持。
