摘要
      尽管地下水环境作为饮用水资源很重要，但目前还没有全面了解地下水中抗生素耐药性基因的全球水平。此外，可能形成地下水抵抗力的生物和非生物因素仍有待在全球范围内探索。在此，我们试图通过对公开可用的全球地下水宏基因组进行计算机重新分析来填补这一知识空白。我们首先研究了抗生素耐药性基因（ARGs）的发生，以确定核心地下水耐药性。我们进一步测试了ARG在原始地下水环境中的传播是否可以用自然生态过程来解释，例如真菌和细菌类群之间的竞争。在高丰度的至少50%的样品中，出现了六种编码氨基糖苷类（aph（3'）、aph（2'））、磺酰胺类（sul1、sul2）和β-内酰胺类（blaOXA、blaTEM）抗性的ARG，从而构成了核心地下水抗性组。ARG丰度在各国之间存在显著差异，仅与细菌群落组成弱相关。虽然只能观察到人为影响的有限影响，但生态相互作用在塑造至少一些核心ARG的丰度模式方面发挥了重要作用。真菌丰度与blaTEM和blaOXA丰度呈正相关，blaTEM和blaOXA是对真菌定期产生的β-内酰胺产生耐药性的ARG。然而，没有确定其余核心ARG的直接相关性。尽管如此，使用共现网络分析，我们发现真菌丰度充当了包括blaOXA和blaTEM的枢纽节点，但也间接促进了氨基糖苷类ARG-aph（3'）的丰度。因此，细菌和真菌之间的相互作用，包括潜在的抗生素生产，可能有助于ARGs在地下水环境中的传播。因此，真菌/细菌SSU比率可以作为原始地下水环境中某些ARG丰度的指标。
Abstract
Despite the importance of groundwater environments as drinking water resources, there is currently no comprehensive picture of the global levels of antibiotic resistance genes in groundwater. Moreover, the biotic and abiotic factors that might shape the groundwater resistome remain to be explored on a global scale. Herein, we attempted to fill this knowledge gap by in silico re-analysis of publicly available global groundwater metagenomes. We first investigated the occurrence of antibiotic resistance genes (ARGs) to define the core groundwater resistome. We further tested whether the ARG dissemination in the pristine groundwater environments could be explained by natural ecological processes such as competition between fungal and bacterial taxa. Six ARGs encoding resistance to aminoglycosides (aph(3’), aph(3’’)), sulfonamides (sul1, sul2), and β-lactams (blaOXA, blaTEM) occurred in at least 50% of samples at high abundance, thereby constituting the core groundwater resistome. ARG abundances differed significantly between countries and only weakly correlated with bacterial community composition. While only limited effects of anthropogenic impacts could be observed, ecological interactions played a significant role in shaping the abundance patterns of at least a number of the core ARGs. Fungal abundance positively correlated with blaTEM and blaOXA abundance, ARGs that confer resistance to β-lactams, regularly produced by fungi. However, no direct correlation was determined for the remainder of the core ARGs. Still, using co-occurrence network analysis we identified that the fungal abundance acted as a hub-node that included blaOXA and blaTEM, but also indirectly contributed to the abundance of aminoglycoside ARG aph(3’). Hence, interactions between bacteria and fungi including potential antibiotic production can contribute to the dissemination of ARGs in groundwater environments. Consequently, fungal/bacterial SSU ratio could serve as an indicator for the abundance of certain ARGs in the pristine groundwater environments.

https://www.biorxiv.org/content/10.1101/2022.11.14.516424v1.abstract