The greater abundances of antibiotic resistance genes (ARGs) in point-of-use tap and reclaimed water than that in freshly treated water raise the question whether residual disinfectants in distribution systems facilitate the spread of ARGs. This study investigated three widely used disinfectants (free chlorine, chloramine, and hydrogen peroxide) on promoting ARGs transfer within Escherichia coli strains and across genera from Escherichia coli to Salmonella typhimurium. The results demonstrated that subinhibitory concentrations (lower than minimum inhibitory concentrations [MICs]) of these disinfectants, namely 0.1-1 mg/L Cl for free chlorine, 0.1-1 mg/L Cl for chloramine, and 0.24-3 mg/L HO, led to concentration-dependent increases in intragenera conjugative transfer by 3.4-6.4, 1.9-7.5, and 1.4-5.4 folds compared with controls, respectively. By comparison, the intergenera conjugative frequencies were slightly increased by approximately 1.4-2.3 folds compared with controls. However, exposure to disinfectants concentrations higher than MICs significantly suppressed conjugative transfer. This study provided evidence and insights into possible underlying mechanisms for enhanced conjugative transfer, which involved intracellular reactive oxygen species formation, SOS response, increased cell membrane permeability, and altered expressions of conjugation-relevant genes. The results suggest that certain oxidative chemicals, such as disinfectants, accelerate ARGs transfer and therefore justify motivations in evaluating disinfection alternatives for controlling antibiotic resistance. This study also triggers questions regarding the potential role of environmental chemicals in the global spread of antibiotic resistance.

It is a challenge to synthesize all-in-one molecular networks that are autonomously self-healable over a wide temperature range (from subzero to high), transparent, stretchable, and conductive. Here we demonstrate the fabrication of selfhealing, transparent, conductive, and highly stretchable elastomers by a photoinitiated copolymerization of two polymerizable deep eutectic solvent (PDES) monomers, acrylic amide (AAm)/choline chloride (ChCl) and maleic acid (MA)/ChCl type PDESs. Hydrogen bonds between binary building blocks of the poly-(AAm/ChCl-co-MA/ChCl) system can readily break and reform, allowing such all organic designed elastomers to self-heal over a wide temperature ranging from −23 to 60 °C while keep a highly transparent appearance. The hypermolecular network elastomers showed a fast self-healing property (within 2 s) without any other external stimuli and excellent self-healing efficiency (up to 94%). The elastomers were highly transparent (an average transmittance of 95.1%), intrinsically conductive (an ionic conductivity of 4.0 × 10 −4 S cm −1 ), and stretchable (strains up to 450%) at room temperature. We hypothesize that this behavior will find their potential use in display and/or optically related fields of stretchable electronics in harsh environments.

Although widespread antibiotic resistance has been mostly attributed to the selective pressure generated by overuse and misuse of antibiotics, recent growing evidence suggests that chemicals other than antibiotics, such as certain metals, can also select and stimulate antibiotic resistance via both co-resistance and cross-resistance mechanisms. For instance, tetL, merE, and oprD genes are resistant to both antibiotics and metals. However, the potential de novo resistance induced by heavy metals at environmentally-relevant low concentrations (much below theminimum inhibitory concentrations [MICs], also referred as sub-inhibitory) has hardly been explored. This study investigated and revealed that heavy metals, namely Cu(II), Ag(I), Cr(VI), and Zn(II), at environmentally-relevant and sub-inhibitory concentrations, promoted conjugative transfer of antibiotic resistance genes (ARGs) between E. coli strains. The mechanisms of this phenomenon were further explored, which involved intracellular reactive oxygen species (ROS) formation, SOS response, increased cell membrane permeability, and altered expression of conjugation-relevant genes. These findings suggest that sub-inhibitory levels of heavy metals that widely present in various environments contribute to the resistance phenomena via facilitating horizontal transfer of ARGs. This study provides evidence from multiple aspects implicating the ecological effect of low levels of heavy metals on antibiotic resistance dissemination and highlights the urgency of strengthening efficacious policy and technology to control metal pollutants in the environments.