Abstract
A global survey was performed with 122 aquatic metagenomic DNA datasets (92 lake water and 30 seawater) obtained from the Sequence Read Archive (SRA). Antibiotic resistance genes (ARGs) and metal resistance genes (MRGs) were derived from the dataset sequences via bioinformatic analysis. The relative abundances of ARGs and MRGs in lake samples were in the ranges ND (not detected)–1.34 × 100 and 1.22 × 10−3–1.98 × 10−1 copies per 16S rRNA, which were higher than those in seawater samples. Among ARGs, multidrug resistance genes and bacitracin resistance genes had high relative abundances in both lake and sea water samples. Multi-metal resistance genes, mercury resistance genes and copper resistance genes had the greatest relative abundance for MRGs. No significant difference was found between epilimnion and hypolimnion in abundance or the Shannon diversity index for ARGs and MRGs. Principal coordinates analysis and permutational multivariate analysis of variance (PERMANOVA) test showed that stratification and geography had significant influence on the composition of ARGs and MRGs in lakes (p < 0.05, PERMANOVA). Coastal seawater samples had significantly greater relative abundance and a higher Shannon index for both ARGs and MRGs than deep ocean and Antarctic seawater samples (p < 0.05, Kruskal-Wallis one-way ANOVA), suggesting that human activity may exert more selective pressure on ARGs and MRGs in coastal areas than those in deep ocean and Antarctic seawater.
Highlights
Antibiotic resistance genes (ARGs) and metal resistance genes have ancient origin (Jackson and Dugas, 2003; Wright and Poinar, 2012), but human activities accelerate the propagation and dissemination of ARGs and MRGs (Gillings, 2018; Li et al, 2017)
The relative abundance of ARGs in seas was in the range ND–1.40 × 10−1 copies per 16S rRNA with an average value of 2.70 × 10−2 copies per 16S rRNA
BacA was the main subtype detected in the lake water and seawater (Tables S3 and S4) with very high relative abundance. bacA has been recently renamed as UppP, an abbreviation of undecaprenyl pyrophosphate phosphatase21, which may be bacterial intrinsic because its homologues can be found in 153 genera (Antibiotic Resistance Genes Database) (Hu et al, 2013)
Summary
Antibiotic resistance genes (ARGs) and metal resistance genes have ancient origin (Jackson and Dugas, 2003; Wright and Poinar, 2012), but human activities accelerate the propagation and dissemination of ARGs and MRGs (Gillings, 2018; Li et al, 2017). Aquatic environments which were influenced by human activities and regarded as ideal mediums for the aggregation and dissemination of ARGs and MRGs (Marti et al, 2014; Pal et al, 2015). Lakes and oceans are two aquatic environments in which ARGs and MRGs collect. ARGs and MRGs could be co-selected or cross-selected in the environment. Analysis of 5436 complete bacterial genomes showed that co-existent ARGs and MRGs occur widely in environmental and clinical bacteria (Luo et al, 2017). Plasmids containing both MRGs and ARGs were more likely to be conjugative and transferred between different bacterial taxa (Pal et al, 2015). The co-occurrence of MRGs and ARGs genes in the same
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