Abstract
Primary succession of plant and microbial communities in the glacier retreating foreland has been extensively studied, but shifts of antibiotic resistance genes (ARGs) with the glacier retreating due to global warming remain elusive. Unraveling the diversity and succession features of ARGs in pristine soil during glacier retreating could contribute to a mechanistic understanding of the evolution and development of soil resistome. In this study, we quantified the abundance and diversity of ARGs along a 50-year soil development chronosequence by using a high-throughput quantitative PCR (HT-qPCR) technique. A total of 24 ARGs and two mobile genetic elements (MGEs) were detected from all the glacier samples, and the numbers of detected ARGs showed a unimodal pattern with an increasing trend at the early stage (0∼8 years) but no significant change at later stages (17∼50 years). The oprJ and mexF genes encoding multidrug resistance were the only two ARGs that were detected across all the succession ages, and the mexF gene showed an increasing trend along the succession time. Structural equation models indicated the predominant role of the intI1 gene encoding the Class 1 integron-integrase in shaping the variation of ARG profiles. These findings suggested the presence of ARGs in pristine soils devoid of anthropogenic impacts, and horizontal gene transfer mediated by MGEs may contribute to the succession patterns of ARGs during the initial soil formation stage along the chronosequence.
Highlights
The development and dissemination of antibiotic resistance is one of the grand challenges for global public health (WHO, 2014)
The genetic features of antibiotic resistance can be transferred between species through horizontal gene transfer (HGT) mediated by mobile genetic elements (MGEs), which can increase the epidemiological risks of environmental antibiotic resistance genes (ARGs) (Parnanen et al, 2016; Levin-Reisman et al, 2017)
The high-throughput quantitative PCR (HT-qPCR) array detected a total of 26 genes from the soil samples
Summary
The development and dissemination of antibiotic resistance is one of the grand challenges for global public health (WHO, 2014). Majority of previous studies focused on the dissipation and fate of antibiotic resistance genes (ARGs) in habitats influenced by anthropogenic activities, including agricultural soils (Kopmann et al, 2013), heavy metal-contaminated soils (Fahrenfeld et al, 2014; Forsberg et al, 2014), rivers (Ouyang et al, 2015), and animal farms (Zhu et al, 2013). Understanding the prevalence and dissemination of ARGs in natural environments with minimal anthropogenic impacts is essential to unravel the origins and evolution of antibiotic resistance, and may contribute to the prediction of the ARG dispersal risk and the development of mitigation strategies (Martínez et al, 2007; Cytryn, 2013)
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