The emergence of antibiotic resistance genes (ARGs) is a great risk to the ecosystem and human health; however, there are rare systematic studies about the characterization and source identification of ARGs in continental rivers. This study examined the occurrence of bacterial communities and ARGs in the water and soil of the Ili River using bacterial testing and metagenomic sequencing. Total dissolved solids (TDSs) and total bacterial count significantly increased from upstream to downstream sites. Enterococcus showed the highest abundance in Cockdara. Metagenomic sequencing revealed that the bacterial communities of surface water were different from those of nearshore soils. Among the top 10 ARGs, fluoroquinolone and aminoglycoside resistance genes exhibited dominant relative abundance, but only the multidrug resistance gene adeF was common in all water and soil samples. Proteobacteria carried almost 61% of ARGs, suggesting that these could be the main antibiotic-resistant bacteria (ARB) in the Ili River. Proteobacteria and ARB were mainly distributed in Yining city and Cockdara. Furthermore, the distribution pattern among the five sampling sites indicated that human activity and animal husbandry greatly contributed to the ARB and ARG contamination. This study first investigated the occurrence and distribution pattern of ARGs in the Ili River, demonstrating a clear correlation between bacteria and ARGs, and ARGs and mobile genetic elements (MGEs).
The enrichment and spread of antibiotic resistance genes
(ARGs)
induced by environmental chemical pollution further exacerbated the
threat to human health and ecological safety. Several compounds are
known to induce R plasmid-mediated conjugation through inducing reactive
oxygen species (ROS), increasing cell membrane permeability, enhancing
regulatory genes expression, and so forth. Up to now, there has been
no substantial breakthrough in the studies of models and related mechanisms.
Here, we established a new conjugation model using pheromone-responsive
plasmid pCF10 and confirmed that five kinds of bisphenols (BPs) at
environmentally relevant concentrations could significantly promote
the conjugation of ARGs mediated by plasmid pCF10 in E. faecalis by up to 4.5-fold compared with untreated
cells. Using qPCR, gene knockout and UHPLC, we explored the mechanisms
behind this phenomenon using bisphenol A (BPA) as a model of BPs and
demonstrated that BPA could upregulate the expression of pheromone,
promote bacterial aggregation, and even directly activate conjugation
as a pheromone instead of producing ROS and enhancing cell membrane
permeability. Interestingly, the result of mathematical analysis showed
that the pheromone effect of most BPs is more potent than that of
synthetic pheromone cCF10. These findings provide new insight into
the environmental behavior and biological effect of BPs and provided
new method and theory to study on enrichment and spread of ARGs induced
by environmental chemical pollution.
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