Low concentrations with high impact: Understanding the spread of antibiotic resistance in aquatic ecosystems (ANTRAQ)

细菌中抗生素耐药性（AR）的快速传播是人类面临的主要挑战之一（WHO, 2014）。虽然在医学上更严格地使用抗生素可能会延缓或减少急性呼吸道感染的传播，但人们普遍认为，该问题的环境方面不容忽视。特别是，迫切需要更好地了解包括地表水在内的环境系统中驱动AR持续存在和扩散的机制。最近的一些研究发现，废水是抗生素耐药细菌及其基因释放到水生环境的主要途径之一。除了各种物质的残留物，抗生素的痕迹在处理后的废水中无处不在。目前的研究已产生证据表明，即使是远低于治疗水平的低浓度抗生素，也能促进耐药基因在微生物种群中的传播。然而，现有的所有研究都集中在亚抑制性抗生素浓度对单一菌株或仅由少数物种组成的人工群落的影响上。因此，低抗生素浓度对复杂水生生态系统微生物组和抗性组的影响仍有待发现。所提出的研究旨在填补这一空白的知识依靠创新的方法的epicPCR。该方法首次允许在物种水平上追踪AR基因在高度多样化的群落中的传播。利用外链pcr，将监测暴露于低浓度抗生素的多种微生物群落所居住的微生物群落，以跟踪群落组成和AR基因分布的变化。微观实验特别适合回答关键致病菌株能否在环境条件下获得AR基因这一“热门问题”。这些微观研究将辅以一系列的批量实验，旨在揭示基因组结构与细菌获得质粒携带的AR基因的能力之间的联系。

The fast spread of antibiotic resistance (AR) in bacteria is one of the major challenges humankind is faced with (WHO, 2014). Although a more restrictive use of antibiotics in medicine might retard or reduce the spread of AR, it is widely accepted that the environmental dimension of the problem cannot be ignored. In particular, a better understanding of the mechanisms driving persistence and proliferation of AR in environmental systems, including surface waters, is urgently needed. Several recent studies identified wastewater as one of the major pathways through which antibiotic-resistant bacteria and the respective genes are released to the aquatic environment. Besides the residues of various substances, traces of antibiotics are omnipresent in treated wastewater. Current research has produced evidence that even low concentrations of antibiotics, far below therapeutic levels, can promote the spread of resistance genes in microbial populations. However, all existing studies focused on the impact of sub-inhibitory antibiotic concentrations on single bacterial strains or artificial communities comprising just a small number of species. Consequently, the impact of low antibiotic concentrations on the microbiome and resistome of complex aquatic ecosystems remains to be uncovered. The proposed research is targeted at filling this gap of knowledge relying on the innovative method of epicPCR. For the first time, this method allows to trace the spread of AR genes in highly diverse communities at species-level. Using epicPCR, microcosms inhabited by a diverse microbial community exposed to low concentrations of antibiotics will be monitored over time in order to track changes in both the community's composition and the distribution of AR genes. The microcosm experiments are particularly suited to answer the 'hot question' of whether critical pathogenic strains can acquire AR genes under environmental conditions. The microcosm studies will be complemented by a series of batch experiments aimed to unravel the link between genomic structures and the ability of bacteria to acquire plasmid-borne AR genes.