摘要
      城市污水污泥是抗生素抗性基因（ARGs）的储存库，通常被堆肥作为肥料用于农业应用，尤其是在干旱和半干旱地区。细胞内ARG（iARGs）和细胞外ARG（eARGs）在堆肥过程中的进化模式及其长期施用堆肥后对土壤盐碱化的反应先前尚不清楚，本研究对此进行了系统研究。还评估了eARGs和iARGs随农田土壤盐碱化的变化和传播风险。细胞外/细胞内ARGs的相对丰度在堆肥过程中变化很大。通常，在整个堆肥过程中，无细胞eARGs（f-eARGs）和细胞吸附eARGs的相对丰度分别比iARGs高4.62倍和3.54倍（中位数），即使在污泥堆肥之前也是如此（错误发现率，FDR p<0.05）。f-eARG和a-eARGs之间的相对丰度没有显著差异。eARGs的相对丰度随着堆肥时间的推移逐渐降低，但相对高于iARGs。值得注意的是，iARGs在成熟阶段出现反弹。然而，超过十年的富含eARG的堆肥应用导致土壤中iARGs的污染比eARGs严重得多。土壤盐碱化使eARGs显著增加943.34倍（FDR p<0.05）。堆肥和土壤盐碱化过程中ARGs的变化与微生物群落结构的变化密切相关。在堆肥中，主要与ARGs相互作用的细菌群落是厚壁菌门（54个独特属和35个共享的核心属）；在土壤盐碱化过程中，在ARGs中发挥主要作用的细菌群落是变形杆菌属（116个独特的核心属和53个共享的核心属）和放线菌属（52个独特的和27个共享的中心属）。这些发现对于评估ARGs在干旱和半干旱地区农田堆肥应用中的传播风险很重要。
Abstract
Municipal sewage sludge, a reservoir of antibiotic resistance genes (ARGs), is usually composted as fertilizer for agricultural application especially in arid and semi-arid areas. The evolution patterns of intracellular ARGs (iARGs) and extracellular ARGs (eARGs) during composting and their responses to soil salinization after long-term compost application kept unclear previously, which were systematically studied in the current study. The variation and dissemination risk of eARGs and iARGs with the salinization of farmland soils was also evaluated. Extra/intra-cellular ARGs relative abundance varied drastically through composting process. Generally, the relative abundance of the cell-free eARGs (f-eARGs) and the cell-adsorbed eARGs (a-eARGs) were 4.62 and 3.54 folds (median) higher than that of iARGs, respectively, during the entire composting process, which held true even before the sludge composting (false discovery rate, FDR p < 0.05). There was no significant difference in relative abundance between f-eARGs and a-eARGs. The relative abundance of eARGs gradually decreased with composting time but was relatively higher than iARGs. It was worth noting that iARGs rebounded in the maturation phase. However, an over ten-year application of the eARG-rich compost led to much more severe contamination of iARGs than eARGs in soil. Soil salinization caused remarkable rise of eARGs by 943.34-fold (FDR p < 0.05). The variation of ARGs during composting and soil salinization was closely related to the change of microbial community structure. In compost, the bacterial communities mainly interacting with ARGs were the Firmicutes (54 unique and 35 shared core genera); and the bacterial communities playing major roles in ARGs during soil salinization were Proteobacteria (116 unique and 53 shared core genera) and Actinobacteria (52 unique and 27 shared core genera). These findings are important for assessing the transmission risk of ARGs in compost application to farmland in arid and semi-arid areas.

https://www.sciencedirect.com/science/article/abs/pii/S0048969722033605