Qing-Lin Chen,Dong Zhu,Xin-Li An,Jing Ding,Yong-Guan Zhu,Li Cui
Growing evidences have demonstrated that heavy metal contamination can promote the proliferation of antibiotic resistance genes (ARGs) via co-selection. However, effects of nano-metal-materials on the occurrence and level of ARGs in the soil and plant, have not been fully explored. To gain insights into this impact, we conducted a pot experiment by adding nano‑silver particles (AgNPs) as a stimuli and Ag ion (AgNO 3 ) and tetracycline as a comparison. By using high throughput quantitative PCR, our results indicated that application of AgNPs (~20 nm and ~50 nm) at a concentration of 100 ppm resulted in no significant changes in the abundance of ARGs in either soil or phyllosphere ( P > 0.05). Nevertheless, the overall pattern of resistome, especially in soil, was shifted following AgNPs application, with a significance increase in the relative abundance of efflux pumps genes, which is an important mechanism for co-selection of ARGs by heavy metals. By comparison, Ag ion at an equivalent Ag mass of AgNPs markedly increased ARGs abundance and shifted ARGs profile in soil, indicating that free Ag ion had a stronger impact on ARGs than AgNPs. These findings provide new insights in assessing the risks of manufactured nanomaterials accumulated in the environment.
Emerging contaminants, such as engineered metal oxide nanoparticles (NPs) and antibiotic resistance genes (ARGs), were reported to be accumulated in waste activated sludge. In this study, the potential impacts of CuO and ZnO NPs on the fate of ARGs during sludge anaerobic digestion were assessed. Metagenomic results showed that the presence of CuO or ZnO NPs increased ARG abundance but had no significant effects on the percentages of resistance mechanisms and types. Further functional analysis of the metagenomes revealed that signal transduction was stimulated by both NPs, especially two-component regulatory systems (TCRS) responsible for quorum sensing (QS), pili synthesis and metal tolerance. Moreover, it was found that the activated QS was closely associated with the shifted bacterial communities, especially enriched genera, such as Acidovorax, Burkholderia, Pseudomonas and Rhodobacter, which were not only the producers of QS signals but also the hosts of ARGs. Meanwhile, the triggered pili synthesis, combined with the increased abundance of mobile genetic elements (plasmids, integrons and insertion sequences), would facilitate the transfer of ARGs among diverse bacteria. Furthermore, the induced resistance to copper/zinc and other metals, such as mercury and arsenic, probably promoted the co-selection between metal and antibiotic resistance. The above results indicated that the propagation of ARGs in digesters might be driven by the NP-stimulated signal transduction. These findings may bring new insights into the understanding of ARG responses to diverse environmental stimuli.
Jie-Yi Zeng,Wei Li,Jian-Qiang Su,Yan-Zi Wang,Yaying Li,Huaiying Yao
Disinfectants and antibiotics are widely used for the prevention and control of bacterial infectious diseases. Frequent disinfection is thought to exacerbate antibiotic resistance. However, little is known about how disinfectants and antibiotics co-induce changes in the soil antibiotic resistance genes (ARGs). This study determined the ARG profiles and bacterial community dynamics between unamended soil and manure-amended soil exposed to benzalkonium chloride (C 12 ) (BC, 10 mg kg −1 ) disinfectant and sulfamethazine (SMZ, 1 mg kg −1 ), using high-throughput quantitative PCR and 16 S rRNA gene sequencing. Manure application enriched the soil in terms of ARGs abundance and diversity, which synergistically amplified the co-selection effect of BC and SMZ on soil antibiotic resistome. Compared with the control treatment, BC and SMZ exposure had a smaller impact on the bacterial infectious diseases and antimicrobial resistance-related functions in manure-amended soil, in which bacterial communities with greater tolerance to antimicrobial substances were constructed. Manure application increased the proportion of rank I ARGs and potential human pathogenic bacteria, while BC and SMZ exposure increased the drug-resistant pathogens transmission risk. This study validated that BC and SMZ aggravated the antimicrobial resistance under manure application, providing a reference for managing the spread risk of antimicrobial resistance in agricultural activities.
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