Extracellular Polymeric Substances Acting as a Permeable Barrier Hinder the Lateral Transfer of Antibiotic Resistance Genes. - Related Documents




#
Rank
Similarity
Title + Abs.
Year
PMID
012345
850601.0000Extracellular Polymeric Substances Acting as a Permeable Barrier Hinder the Lateral Transfer of Antibiotic Resistance Genes. Antibiotic resistance genes (ARGs) in bacteria are emerging contaminants as their proliferation in the environment poses significant threats to human health. It is well recognized that extracellular polymeric substances (EPS) can protect microorganisms against stress or damage from exogenous contaminants. However, it is not clear whether EPS could affect the lateral transfer of ARGs into bacteria, which is one of the major processes for the dissemination of ARGs. This study investigated the lateral transfer of ARGs carried by plasmids (pUC19, pHSG298, and pHSG396) into competent Escherichia coli cells with and without EPS. Transformant numbers and transformation efficiency for E. coli without EPS were up to 29 times of those with EPS at pH 7.0 in an aqueous system. The EPS removal further increased cell permeability in addition to the enhanced cell permeability by Ca(2+), which could be responsible for the enhanced lateral transfer of ARGs. The fluorescence quenching experiments showed that EPS could strongly bind to plasmid DNA in the presence of Ca(2+) and the binding strength (LogK (A) = 10.65-15.80 L mol(-1)) between EPS and plasmids was positively correlated with the enhancement percentage of transformation efficiency resulting from the EPS removal. X-ray photoelectron spectroscopy (XPS) analyses and model computation further showed that Ca(2+) could electrostatically bind with EPS mainly through the carboxyl group, hydroxyl group, and RC-O-CR in glucoside, thus bridging the plasmid and EPS. As a result, the binding of plasmids with EPS hindered the lateral transfer of plasmid-borne ARGs. This study improved our understanding on the function of EPS in controlling the fate and transport of ARGs on the molecular and cellular scales.201931057498
677710.9998Unveiling the role of uranium in enhancing the transformation of antibiotic resistance genes. Transformation represents one of the most important pathways for the horizontal transfer of antibiotic resistance genes (ARGs), which enables competent bacteria to acquire extracellular ARGs from the surrounding environment. Both heavy metals and irradiation have been demonstrated to influence the bacterial transformation process. However, the impact of ubiquitously occurring radioactive heavy metals on the transformation of ARGs remains largely unknown. Here, we showed that a representative radioactive nuclide, uranium (U), at environmental concentrations (0.005-5 mg/L), improved the transformation frequency of resistant plasmid pUC19 into Escherichia coli by 0.10-0.85-fold in a concentration-dependent manner. The enhanced ARGs transformation ability under U stress was demonstrated to be associated with reactive oxygen species (ROS) overproduction, membrane damage, and up-regulation of genes related to DNA uptake and recombination. Membrane permeability and ROS production were the predominant direct and indirect factors affecting transformation ability, respectively. Our findings provide valuable insight into the underlying mechanisms of the impacts of U on the ARGs transformation process and highlight concerns about the exacerbated spread of ARGs in radioactive heavy metal-contaminated ecosystems, especially in areas with nuclear activity or accidents.202439208634
677820.9997Bisphenol S Promotes the Transfer of Antibiotic Resistance Genes via Transformation. The antibiotic resistance crisis has seriously jeopardized public health and human safety. As one of the ways of horizontal transfer, transformation enables bacteria to acquire exogenous genes naturally. Bisphenol compounds are now widely used in plastics, food, and beverage packaging, and have become a new environmental pollutant. However, their potential relationship with the spread of antibiotic resistance genes (ARGs) in the environment remains largely unexplored. In this study, we aimed to assess whether the ubiquitous bisphenol S (BPS) could promote the transformation of plasmid-borne ARGs. Using plasmid pUC19 carrying the ampicillin resistance gene as an extracellular ARG and model microorganism E. coli DH5α as the recipient, we established a transformation system. Transformation assays revealed that environmentally relevant concentrations of BPS (0.1-10 μg/mL) markedly enhanced the transformation frequency of plasmid-borne ARGs into E. coli DH5α up to 2.02-fold. Fluorescent probes and transcript-level analyses suggest that BPS stimulated increased reactive oxygen species (ROS) production, activated the SOS response, induced membrane damage, and increased membrane fluidity, which weakened the barrier for plasmid transfer, allowing foreign DNA to be more easily absorbed. Moreover, BPS stimulates ATP supply by activating the tricarboxylic acid (TCA) cycle, which promotes flagellar motility and expands the search for foreign DNA. Overall, these findings provide important insight into the role of bisphenol compounds in facilitating the horizontal spread of ARGs and emphasize the need to monitor the residues of these environmental contaminants.202439337307
860430.9997Reactive chlorine species inhibiting interspecies spread of antibiotic resistance via disrupting donor - Recipient cells and regulating plasmid conjugation genes. Current drinking water treatment plant (DWTP) disinfection technologies face limitations, allowing plasmid-mediated antibiotic resistance genes (ARGs) transfer to occur among viable but nonculturable (VBNC) bacteria, heightening the risk of antibiotic-resistant infections. While UV/Chlorine has been adopted to curb ARGs abundance, its impacts on the interspecies transfer of ARG-carrying plasmids remain hardly explored. This study investigated how reactive chlorine species (RCS) in the UV/Chlorine system inhibited the transfer of antibiotic resistance from antibiotic-resistant Escherichia coli (AR E. coli) to Bacillus subtilis (B.S) by inactivating both donor and recipient strains and regulating plasmid conjugation genes. RCS reduced plasmid transfer frequencies by 2.1-log and 3.2-log compared to UV or chlorine alone. By impairing (•)OH scavenging ability, it led to ROS accumulation in AR E. coli, disrupting cellular energy metabolism and DNA repair, ultimately causing DNA degradation and membrane damage, resulting in AR E. coli inactivation rather than entering the VBNC state. Additionally, RCS induced structural and intracellular disruption in B.S, compromising its capacity for plasmid uptake and stable maintenance. Finally, RCS inhibited plasmid horizontal transfer while enhancing vertical transfer, with its damage to outer membrane proteins further restricting interspecies plasmid conjugation transfer. This study provides novel insights for DWTPs to better control ARGs interspecies transfer and improve drinking water safety.202540505407
849940.9997Inhibited conjugative transfer of antibiotic resistance genes in antibiotic resistant bacteria by surface plasma. Antibiotic resistant bacteria (ARB) and resistance genes (ARGs) are emerging environmental pollutants with strong pathogenicity. In this study, surface plasma was developed to inactivate the donor ARB with Escherichia coli (AR E. coli) as a model, eliminate ARGs, and inhibit conjugative transfer of ARGs in water, highlighting the influences of concomitant inorganic ions. Surface plasma oxidation significantly inactivated AR E. coli, eliminated ARGs, and inhibited conjugative transfer of ARGs, and the presence of NO(3)(-), Cu(2+), and Fe(2+) all promoted these processes, and SO(4)(2-) did not have distinct effect. Approximately 4.5log AR E. coli was inactivated within 10 min treatment, and it increased to 7.4log AR E. coli after adding Fe(2+). Integrons intI1 decreased by 3.10log (without Fe(2+)) and 4.43log (adding Fe(2+)); the addition of Fe(2+) in the surface plasma induced 99.8% decline in the conjugative transfer frequency. The inhibition effects on the conjugative transfer of ARGs were mainly attributed to the reduced reactive oxygen species levels, decreased DNA damage-induced response, decreased intercellular contact, and down-regulated expression of plasmid transfer genes. This study disclosed underlying mechanisms for inhibiting ARGs transfer, and supplied a prospective technique for ARGs control.202134536683
677650.9997Natural sphalerite nanoparticles can accelerate horizontal transfer of plasmid-mediated antibiotic-resistance genes. Minerals and microorganisms are integral parts of natural environments, and they inevitably interact. Antibiotic-resistance genes (ARGs) significantly threaten modern healthcare. However, the effects of natural minerals on ARG propagation in aquatic systems are not fully understood. The present work studied the effects of natural sphalerite (NS) nanoparticles on the horizontal transfer of ARGs from Escherichia coli DH5α (CTX) (donor) to E. coli C600 (Sm) (recipient), and from E. coli DH5α (MCR) (donor) to E. coli C600 (Sm), and their underlying mechanisms. NS particles (0.5-50 mg L(-1)) induced an NS-concentration-dependent increase in conjugative transfer frequency. The underlying mechanisms associated with the facilitated ARG transfer included the production of intracellular reactive oxygen species, the SOS response, changes in bacterial cell morphology, and alteration of mRNA levels of bacterial cell membrane protein-related genes and genes associated with conjugative ARG transfer. The information herein offers new mechanistic understanding of risks of bacterial resistance resulting from NS.202031999971
676460.9997Chlorine disinfection promotes the exchange of antibiotic resistance genes across bacterial genera by natural transformation. Chlorine disinfection to drinking water plays an important role in preventing and controlling waterborne disease outbreaks globally. Nevertheless, little is known about why it enriches the antibiotic resistance genes (ARGs) in bacteria after chlorination. Here, ARGs released from killed antibiotic-resistant bacteria (ARB), and culturable chlorine-injured bacteria produced in the chlorination process as the recipient, were investigated to determine their contribution to the horizontal transfer of ARGs during disinfection treatment. We discovered Escherichia coli, Salmonella aberdeen, Pseudomonas aeruginosa and Enterococcus faecalis showed diverse resistance to sodium hypochlorite, and transferable RP4 could be released from killed sensitive donor consistently. Meanwhile, the survival of chlorine-tolerant injured bacteria with enhanced cell membrane permeabilisation and a strong oxidative stress-response demonstrated that a physiologically competent cell could be transferred by RP4 with an improved transformation frequency of up to 550 times compared with the corresponding untreated bacteria. Furthermore, the water quality factors involving chemical oxygen demand (COD(Mn)), ammonium nitrogen and metal ions (Ca(2+) and K(+)) could significantly promote above transformation frequency of released RP4 into injured E. faecalis. Our findings demonstrated that the chlorination process promoted the horizontal transfer of plasmids by natural transformation, which resulted in the exchange of ARGs across bacterial genera and the emergence of new ARB, as well as the transfer of chlorine-injured opportunistic pathogen from non-ARB to ARB. Considering that the transfer elements were quite resistant to degradation through disinfection, this situation poses a potential risk to public health.202032327733
860770.9997Different paths, same destination: Bisphenol A and its substitute induce the conjugative transfer of antibiotic resistance genes. Antibiotic resistance genes are primarily spread through horizontal gene transfer in aquatic environments. Bisphenols, which are widely used in industry, are pervasive contaminants in such environments. This study investigated how environmentally relevant concentrations of bisphenol A and its substitute (bisphenol S, Bisphenol AP and Bisphenol AF) affect the spread of antibiotic resistance genes among Escherichia coli. As a result, bisphenol A and its three substitutes were found to promote the RP4 plasmid-mediated conjugative transfer of antibiotic resistance genes with different promotive efficiency. Particularly, bisphenol A and bisphenol S were found to induce more than double the incidence of conjugation at 0.1 nmol/L concentration. They therefore were selected as model compounds to investigate the involved mechanisms. Surprisingly, both slightly inhibited bacterial activity, but there was no significant increase in cell death. Bisphenols exposure changed the polymeric substances excreted by the bacteria, increased the permeability of their cell membranes, induced the secretion of antioxidant enzymes and generated reactive oxygen species. They also affected the expression of genes related to conjugative transfer by upregulating replication and DNA transfer genes and downregulating global regulatory genes. It should be noted that gene expression levels were higher in the BPS-exposed group than in the BPA-exposed group. The synthesis of bacterial metabolites and functional components was also significantly affected by bisphenols exposure. This research has helped to clarify the potential health risks of bisphenol contamination of aquatic environments.202439510271
677580.9997Copper nanoparticles and copper ions promote horizontal transfer of plasmid-mediated multi-antibiotic resistance genes across bacterial genera. The spread of antibiotic resistance has become a major concern for public health. As emerging contaminants, various metallic nanoparticles (NPs) and ionic heavy metals have been ubiquitously detected in various environments. Although previous studies have indicated NPs and ionic heavy metals could exhibit co-selection effects for antibiotic resistance, little is known about whether and how they could promote antibiotic resistance spread via horizontal gene transfer across bacterial genera. This study, we report both CuO NPs and copper ions (Cu(2+)) could stimulate the conjugative transfer of multiple-drug resistance genes. When exposing bacteria to CuO NPs or Cu(2+) at environmental-relevant and sub-inhibitory concentrations (e.g., 1-100 μmol/L), conjugation frequencies of plasmid-encoded antibiotic resistance genes across genera (i.e., from Escherichia coli to Pseudomonas putida) were significantly enhanced (p < 0.05). The over-production of reactive oxygen species played a crucial role in promoting conjugative transfer. Genome-wide RNA and protein sequencing suggested expressional levels of genes and proteins related to oxidative stress, cell membrane permeability, and pilus generation were significantly up-regulated under CuO NPs and Cu(2+) exposure (p < 0.05). This study provides insights in the contributions of NPs and heavy metals on the spread of antibiotic resistance.201931158594
850890.9997Phenolic compounds promote the horizontal transfer of antibiotic resistance genes in activated sludge. Phenolic compounds are common organic pollutants in wastewater. During the wastewater treatment process, these compounds may influence the microbial community structure and functions. However, the impact of the phenolic compounds in the wastewater treatment plants on the horizontal transfer of antibiotic resistance genes (ARGs) has not been well assessed. In this study, we investigated the horizontal transfer of ARGs under the stress of phenolic compounds. The results showed that in pure culture bacteria system, p-nitrophenol (PNP), p-aminophenol (PAP) and phenol (PhOH) (10-100 mg/L) can significantly increase the horizontal transfer frequency of ARGs by 2.2-4.6, 3.6-9.4 and 1.9-9.0 fold, respectively. And, the RP4 plasmid transfer from Escherichia coli HB101 (E. coli HB101) to the bacteria in activated sludge increased obviously under the stress of phenolic compounds. Further investigation revealed that the PNP and PhOH at the concentration of 10-100 mg/L increased the production of reactive oxygen species and the permeability of cell membrane in the donor and recipient, which could be the causes of horizontal transfer of RP4 plasmid. In addition, it was also found that PNP, PAP and PhOH stress inhibit the expression of the global regulatory genes korB and trbA in the RP4 plasmid, and increase the expression level of the traF gene, thereby promoting the conjugative transfer of the RP4 plasmid. Taken together, these results improved our understanding of the horizontal transfer of ARGs under the stress of phenolic compounds and provided basic information for management of the systems that treat wastewater containing phenolic compounds.202134392203
8516100.9997Graphene Oxide Inhibits Antibiotic Uptake and Antibiotic Resistance Gene Propagation. Antibiotics and antibiotic resistance genes (ARGs) in the natural environment have become substantial threats to the ecosystem and public health. Effective strategies to control antibiotics and ARG contaminations are emergent. A novel carbon nanomaterial, graphene oxide (GO), has attracted a substantial amount of attention in environmental fields. This study discovered the inhibition effects of GO on sulfamethoxazole (SMZ) uptake for bacteria and ARG transfer among microorganisms. GO promoted the penetration of SMZ from intracellular to extracellular environments by increasing the cell membrane permeability. In addition, the formation of a GO-SMZ complex reduced the uptake of SMZ in bacteria. Moreover, GO decreased the abundance of the sulI and intI genes by approximately 2-3 orders of magnitude, but the global bacterial activity was not obviously inhibited. A class I integron transfer experiment showed that the transfer frequency was up to 55-fold higher in the control than that of the GO-treated groups. Genetic methylation levels were not significant while sulI gene replication was inhibited. The biological properties of ARGs were altered due to the GO-ARG noncovalent combination, which was confirmed using multiple spectral analyses. This work suggests that GO can potentially be applied for controlling ARG contamination via inhibiting antibiotic uptake and ARG propagation.201627934199
6771110.9997Triclosan at environmental concentrations can enhance the spread of extracellular antibiotic resistance genes through transformation. The dissemination of antibiotic resistance mediated by horizontal transfer of antibiotic resistance genes (ARGs) is exacerbating the global antibiotic crisis. Currently, little is known about whether non-antibiotic, anti-microbial (NAAM) chemicals are associated with the dissemination of ARGs in the environment. In this study, we aimed to evaluate whether a ubiquitous NAAM chemical, triclosan (TCS), is able to promote the transformation of plasmid-borne antibiotic resistance genes (ARGs). By using the plasmid pUC19 carrying ampicillin resistance genes as the extracellular ARG and a model microorganism Escherichia coli DH5ɑ as the recipient, we found that TCS at environmentally detected concentrations (0.2 μg/L to 20 μg/L) significantly enhanced the transformation of plasmid-borne ARGs into E. coli DH5ɑ for up to 1.4-fold. The combination of phenotypic experiments, genome-wide RNA sequencing and proteomic analyses revealed that TCS exposure stimulated the reactive oxygen species (ROS) production for 1.3- to 1.5-fold, induced bacterial membrane damage and up-regulated the translation of outer membrane porin. Moreover, general secretion system Sec (1.4-fold), twin arginine translocation system Tat (1.2-fold) and type IV pilus secretion systems (2.5-fold) were enhanced by TCS, which might contribute to the DNA searching/capture by pilus. Together, TCS might increase the transformation frequency of ARGs into E. coli DH5ɑ by ROS over-production, damaging cell membrane barrier, mediating the pilus capture of plasmid and the translocation of plasmid via cell membrane channels. This study reports that TCS could accelerate the transformation of extracellular ARGs to competent bacteria at environmentally relevant concentrations. The findings advance our understanding of the fate of ARGs in ecosystems and call for risk assessments of NAAM chemicals on disseminating antibiotic resistance.202032019018
8512120.9997Dissolved oxygen facilitates efficiency of chlorine disinfection for antibiotic resistance. Controlling the dissemination of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) is a global concern. While commonly used chlorine disinfectants can damage or even kill ARB, dissolved oxygen (DO) may affect the formation of reactive chlorine species. This leads to the hypothesis that DO may play roles in mediating the effectiveness of chlorine disinfection for antibiotic resistance. To this end, this study investigated the impacts of DO on the efficiency of chlorine disinfection for antibiotic resistance. The results revealed that DO could increase the inactivation efficiency of ARB under chloramine and free chlorine exposure at practically relevant concentrations. Reactive species induced by DO, including H(2)O(2), O(2)(-), and OH, inactivated ARB strains by triggering oxidative stress response and cell membrane damage. In addition, the removal efficiency of extracellular ARGs (i.e. tetA and bla(TEM)) was enhanced with increasing dosage of free chlorine or chloramine under aerobic conditions. DO facilitated the fragmentation of plasmids, contributing to the degradation of extracellular ARGs under exposure to chlorine disinfectants. The findings suggested that DO facilitates disinfection efficiency for antibiotic resistance in water treatment systems.202438750753
8503130.9997Dual-pathway inhibition of antibiotic resistance genes by ferrate (Fe(VI)): Oxidative inactivation and genetic mobility impairment in anaerobically digested sludge. Antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) are emerging environmental contaminants that threaten public health, highlighting the urgent need for effective control strategies. Ferrate (Fe(VI)), a strong and eco-friendly oxidant, shows great potential for this purpose. This study systematically evaluated the efficacy of Fe(VI) in mitigating ARGs and ARB in anaerobically digested sludge, with a particular focus on elucidating the underlying mechanisms by which Fe(VI) effects ARGs dissemination through both vertical gene transfer (VGT) and horizontal gene transfer (HGT). Result shows that Fe(VI) doses of 20 and 60 mg/g-TS reduce ARGs by 9.75 % and 19.12 %, respectively, while inactivating up to 24.7 % of ARB at the higher dose. Pathogenic ARB, such as Escherichia coli and Shigella sonnei, are preferentially removed, with abundances decrease by 63.7 % and 28.0 %. Mechanistically, the structural disruption of bacterial cells caused by Fe(VI) in anaerobically digested sludge, as indicated by a 29 % reduction in extracellular polymeric substances and a 23.7 % increase in cell membrane permeability. Subsequently, a marked release of intracellular ARGs into the extracellular environment is also observed, where they are likely subjected to degradation by Fe(VI). This oxidative killing accounts for the observed ARB decrease, thereby limiting the VGT of ARGs. In addition, Fe(VI) impairs the HGT of ARGs by diminishing their mobility potential, reflected in the reduced co-occurence with mobile genetic elements. Meanwhile, sludge bacterial competence for DNA uptake and recombination is markedly reduced, as evidenced by a 9.8 % decline in the abundance of related functional genes. These findings demonstrate that Fe(VI) effectively inhibits the dissemination of ARGs by targeting both primary transmission pathways. It suppresses VGT, thereby reducing the inheritance of ARB within populations, and limits HGT, curbing the spread of mobile ARGs among competent species. By disrupting these two critical routes, Fe(VI) shows strong potential as an effective strategy for mitigating ARGs propagation in sludge systems.202541138327
8524140.9997Tebuconazole exacerbates co-occurrence and horizontal transfer of antibiotic resistance genes. As one of the most widely used pesticides in the global fungicide market, tebuconazole has become heavily embedded in soil along with antibiotic resistance genes (ARGs). However, it remains unclear whether the selective pressure produced by tebuconazole affects ARGs and their horizontal transfer. In this experiment, we simulated a tebuconazole-contaminated soil ecosystem and observed changes in the abundance of ARGs and mobile genetic element (MGEs) due to tebuconazole exposure. We also established a plasmid RP4-mediated conjugative transfer system to investigate in depth the impact of tebuconazole on the horizontal transfer of ARGs and its mechanism of action. The results showed that under tebuconazole treatment at concentrations ranging from 0 to 10 mg/L, there was a gradual increase in the frequency of plasmid conjugative transfer, peaking at 10 mg/L which was 7.93 times higher than that of the control group, significantly promoting horizontal transfer of ARGs. Further analysis revealed that the conjugative transfer system under tebuconazole stress exhibited strong ability to form biofilm, and the conjugative transfer frequency ratio of biofilm to planktonic bacteria varied with the growth cycle of biofilm. Additionally, scanning electron microscopy and flow cytometry demonstrated increased cell membrane permeability in both donor and recipient bacteria under tebuconazole stress, accompanied by upregulation of ompA gene expression controlling cell membrane permeability. Furthermore, enzyme activity assays indicated significant increases in CAT, SOD activity, and GSH content in recipient bacteria under tebuconazole stress. Moreover, expression levels of transmembrane transporter gene trfAp as well as genes involved in oxidative stress and SOS response were found to be correlated with the frequency of plasmid conjugative transfer.202439277355
6781150.9997Antibiotic-resistance gene transfer in antibiotic-resistance bacteria under different light irradiation: Implications from oxidative stress and gene expression. Due to the significant public health risks, there is substantial scientific interest in the increasing abundance of antibiotic-resistance bacteria (ARB) and the spread of antibiotic-resistance genes (ARGs) in aquatic environments. To clearly understand the mechanism of ARG transfer, this study examined the conjugative transfer of genes encoding resistance to cephalosporin (bla(CTX)) and polymyxin (mcr-1) from two antibiotic-resistant donor strains, namely E. coli DH5α (CTX) and E. coli DH5α (MCR), and to a streptomycin-resistant receptor strain (E. coli C600 (Sm)). Conjugative transfer was specifically studied under different light irradiation conditions including visible light (VL), simulated sunlight (SS) and ultraviolet light (UV(254nm)). Results show that the conjugative transfer frequency was not affected by VL irradiation, while it was slightly improved (2-10 fold) by SS irradiation and extremely accelerated (up to 100 fold) by UV irradiation. Furthermore, this study also explored the link between ARG transfer and stress conditions. This was done by studying physiological and biochemical changes; oxidative stress response; and functional gene expression of co-cultured AR-E. coli strains under stress conditions. When correlated with the transfer frequency results, we found that VL irradiation did not affect the physiological and biochemical characteristics of the bacteria, or induce oxidative stress and gene expression. For SS irradiation, oxidative stress occurred slowly, with a slight increase in the expression of target genes in the bacterial cells. In contrast, UV irradiation, rapidly inactivated the bacteria, the degree of oxidative stress was very severe and the expression of the target genes was markedly up-regulated. Our study could provide new insight into the underlying mechanisms and links between accelerated conjugative transfer and oxidative stress, as well as the altered expression of genes relevant to conjugation and other stress responses in bacterial cells.201930465986
8501160.9997Mechanistic insight of simultaneous removal of tetracycline and its related antibiotic resistance bacteria and genes by ferrate(VI). The emergence of antibiotics and their corresponding antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have posed great challenges to the public health. The paper demonstrates the removal of co-existing tetracycline (TC), its resistant Escherichia coli (E. coli), and ARGs (tetA and tetR) in a mixed system by applying ferrate(VI) (Fe(VI)O(4)(2-), Fe(VI)) at pH 7.0. TC was efficiently degraded by Fe(VI), and the rapid inactivation of the resistant E. coli was found with the complete loss of culturability. The results of flow cytometry suggested that the damage of membrane integrity and respiratory activity were highly correlated with the Fe(VI) dosages. Moreover, high-dose Fe(VI) eliminates 6 log(10) viable but non-culturable (VBNC) cells and even breaks the cells into fragments. ARGs in extracellular form (e-ARGs) exhibited a high sensitivity of 4.44 log(10) removal to Fe(VI). Comparatively, no removal of intracellular ARGs (i-ARGs) was observed due to the multi-protection of cellular structure and rapid decay of Fe(VI). The oxidized products of TC were assessed to be less toxic than the parent compound. Overall, this study demonstrated the superior efficiency and great promise of Fe(VI) on simultaneous removal of antibiotics and their related ARB and ARGs in water.202133984704
8519170.9997Effects of Antibiotic Resistance Genes and Antibiotics on the Transport and Deposition Behaviors of Bacteria in Porous Media. Antibiotics present in the natural environment would induce the generation of antibiotic-resistant bacteria (ARB), causing great environmental risks. The effects of antibiotic resistance genes (ARGs) and antibiotics on bacterial transport/deposition in porous media yet are unclear. By using E. coli without ARGs as antibiotic-susceptible bacteria (ASB) and their corresponding isogenic mutants with ARGs in plasmids as ARB, the effects of ARGs and antibiotics on bacterial transport in porous media were examined under different conditions (1-4 m/d flow rates and 5-100 mM NaCl solutions). The transport behaviors of ARB were comparable with those of ASB under antibiotic-free conditions, indicating that ARGs present within cells had negligible influence on bacterial transport in antibiotic-free solutions. Interestingly, antibiotics (5-1000 μg/L gentamicin) present in solutions increased the transport of both ARB and ASB with more significant enhancement for ASB. This changed bacterial transport induced by antibiotics held true in solution with humic acid, in river water and groundwater samples. Antibiotics enhanced the transport of ARB and ASB in porous media via different mechanisms (ARB: competition of deposition sites; ASB: enhanced motility and chemotaxis effects). Clearly, since ASB are likely to escape sites containing antibiotics, these locations are more likely to accumulate ARB and their environmental risks would increase.202337406198
7981180.9997Dissolved biochar eliminates the effect of Cu(II) on the transfer of antibiotic resistance genes between bacteria. The proliferation of antibiotic resistance genes (ARGs) has posed significant risks to human and environmental health. Research has confirmed that Cu(II) could accelerate the conjugative transfer of ARGs between bacteria. This study found that adding dissolved biochar effectively weakened or eliminated the Cu(II)-facilitated efficient transfer of ARGs. The efficiency of conjugative transfer was promoted after treatment with Cu(II) (0.05 mg/L) or dissolved biochar at a pyrolysis temperature of 300 °C. When exposed to the combination of Cu(II) and dissolved biochar, the transfer frequency was significantly reduced; this occurred regardless of the Cu(II) concentration or pyrolysis temperature of dissolved biochar. In particular, when the Cu(II) concentration exceeded 0.5 mg/L, the transfer efficiency was entirely inhibited. Gene expression analysis indicated that different treatments affect transfer efficiency by regulating the expression of three global regulatory genes: korA, korB, and trbA. Among them, humic acid repressed the expression of these genes; however, Cu(II) formed complex with the humic acid-like components, gradually weakening the inhibitive effect of these components. The promotion of low molecule organic matters dominated, resulting in a dynamic decline in the transfer efficiency. This study provides a new environmental contaminant treatment approach to eliminate the heavy metal-facilitated transfer of ARGs between bacteria.202234583164
8513190.9997Chlorine disinfection facilitates natural transformation through ROS-mediated oxidative stress. The bacterial infection that involves antimicrobial resistance is a rising global threat to public health. Chlorine-based water disinfection processes can inactivate antibiotic resistant bacteria. However, at the same time, these processes may cause the release of antibiotic resistance genes into the water as free DNA, and consequently increase the risk to disseminate antibiotic resistance via natural transformation. Presently, little is known about the contribution of residual chlorine affecting the transformation of extracellular antibiotic resistance genes (ARGs). This study investigates whether chloramine and free chlorine promote the transformation of ARGs and how this may occur. We reveal that both chloramine and free chlorine, at practically relevant concentrations, significantly stimulated the transformation of plasmid-encoded ARGs by the recipient Acinetobacter baylyi ADP1, by up to a 10-fold increase. The underlying mechanisms underpinning the increased transformations were revealed. Disinfectant exposure induced a series of cell responses, including increased levels of reactive oxygen species (ROS), bacterial membrane damage, ROS-mediated DNA damage, and increased stress response. These effects thus culminated in the enhanced transformation of ARGs. This promoted transformation was observed when exposing disinfectant-pretreated A. baylyi to free plasmid. In contrast, after pretreating free plasmid with disinfectants, the transformation of ARGs decreased due to the damage of plasmid integrity. These findings provide important insight on the roles of disinfectants affecting the horizontal transfer of ARGs, which could be crucial in the management of antibiotic resistance in our water systems.202133941886