摘要
      微塑料纤维（MFs）作为污水污泥中最常检测到的微塑料形状，对污泥处理和处置提出了新的关注。然而，在污泥处理过程中，MFs对抗生素抗性基因（ARGs），特别是细胞外ARGs（eARGs）的影响仍远未明确。因此，本研究通过长期运行，研究了污泥厌氧消化（AD）过程中MFs对eARGs的潜在影响，AD是一种常用的污泥处理方法。qPCR结果显示，在污泥AD过程中，eARGs的绝对丰度和相对丰度都随着MFs的暴露而增加。在MFs剂量最高的AD反应器中（170个项目/gTS），8种测试eARG的平均绝对丰度和相关丰度分别是对照AD反应器的1.70倍和2.15倍。宏基因组学结果进一步证实了MFs暴露后污泥厌氧消化过程中eARGs丰度的增加，并且这种增加没有显示出显著的选择性。对eARGs潜在宿主的鉴定表明，eARGs的宿主数量也随着MFs暴露而增加，这可能表明由于eARGs增加，水平转化增强。进一步探索机制表明，参与IV型分泌系统的基因在MFs暴露后上调，这表明eARGs的活性释放随着MFs暴露而增强。相反，MFs可能不会影响eARGs的被动释放，因为它对细胞膜损伤的影响是微不足道的。污泥AD过程中增强的eARGs可能会进一步加速ARGs在环境中的迁移，这在污泥处理和处置过程中应予以考虑。
Abstract
Microplastic fibers (MFs), as the most frequently detected microplastic shape in sewage sludge, have posed emerging concern for sludge treatment and disposal. However, the effect of MFs on antibiotic resistance genes (ARGs), especially extracellular ARGs (eARGs) during sludge treatment remains far from explicit. Therefore, this study investigated the potential impact of MFs on eARGs during sludge anaerobic digestion (AD), a commonly used sludge treatment method, through long-term operation. The qPCR results showed that both absolute and relative abundances of eARGs increased with the MFs exposure during sludge AD. The average absolute and relative abundances of eight tested eARGs in the AD reactor with the highest MFs dosage (170 items/gTS) were 1.70 and 2.15 times higher than those in the control AD reactor. The metagenomics results further comfirmed the increase of eARGs abundance during sludge anaerobic digestion after MFs exposure and the enhancement did not show significant selectivity. The identification of the potential hosts of eARGs suggested the host numbers of eARGs also increased with MFs exposure, which may suggest enhanced horizonal transformation as a result of increased eARGs. Further exploring the mechansims showed that the genes involved in type IV secretion system was upregulated after MFs exposure, suggesting the active release of eARGs was enhanced with MFs exposure. In contrast, the MFs may not affect the passive release of eARGs as its impact on cell membrance damage was insignificant. The enhanced eARGs in sludge AD process may further accelerate the transport of ARGs in environment, which should be considered during sludge treatment and disposal.

https://www.sciencedirect.com/science/article/abs/pii/S0043135422003803