Reactive chlorine species inhibiting interspecies spread of antibiotic resistance via disrupting donor - Recipient cells and regulating plasmid conjugation genes. - Related Documents




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860401.0000Reactive 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
677810.9998Bisphenol 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
851320.9998Chlorine 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
677630.9998Natural 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
852440.9998Tebuconazole 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
676450.9998Chlorine 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
677760.9998Unveiling 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
860570.9998Exposure to bisphenol compounds accelerates the conjugative transfer of antibiotic resistance plasmid. Antimicrobial resistance poses the most formidable challenge to public health, with plasmid-mediated horizontal gene transfer playing a pivotal role in its global spread. Bisphenol compounds (BPs), a group of environmental contaminants with endocrine-disrupting properties, are extensively used in various plastic products and can be transmitted to food. However, the impact of BPs on the plasmid-mediated horizontal transfer of antibiotic resistance genes (ARGs) has not yet been elucidated. Herein, we demonstrate that BPs could promote the conjugative transfer frequency of RP4-7 and clinically multidrug-resistant plasmids. Furthermore, the promoting effect of BPs on the plasmid transfer was also confirmed in a murine model. Microbial diversity analysis of transconjugants indicated an increase in α diversity in the BPAF-treated group, along with the declined richness of some beneficial bacteria and elevated richness of Faecalibaculum rodentium, which might serve as an intermediate repository for resistance plasmids. The underlying mechanisms driving the enhanced conjugative transfer upon BPAF treatment include exacerbated oxidative stress, disrupted membrane homeostasis, augmented energy metabolism, and the increased expression of conjugation-related genes. Collectively, our findings highlight the potential risk associated with the exacerbated dissemination of AMR both in vitro and in vivo caused by BPs exposure.202439278585
860380.9997Ketoprofen promotes the conjugative transfer of antibiotic resistance among antibiotic resistant bacteria in natural aqueous environments. The emergence and spread of antibiotic resistance in the environment pose a serious threat to global public health. It is acknowledged that non-antibiotic stresses, including disinfectants, pharmaceuticals and organic pollutants, play a crucial role in horizontal transmission of antibiotic resistance genes (ARGs). Despite the widespread presence of non-steroidal anti-inflammatory drugs (NSAIDs), notably in surface water, their contributions to the transfer of ARGs have not been systematically explored. Furthermore, previous studies have primarily concentrated on model strains to investigate whether contaminants promote the conjugative transfer of ARGs, leaving the mechanisms of ARG transmission among antibiotic resistant bacteria in natural aqueous environments under the selective pressures of non-antibiotic contaminants remains unclear. In this study, the Escherichia coli (E. coli) K12 carrying RP4 plasmid was used as the donor strain, indigenous strain Aeromonas veronii containing rifampicin resistance genes in Taihu Lake, and E. coli HB101 were used as receptor strains to establish inter-genus and intra-genus conjugative transfer systems, examining the conjugative transfer frequency under the stress of ketoprofen. The results indicated that ketoprofen accelerated the environmental spread of ARGs through several mechanisms. Ketoprofen promoted cell-to-cell contact by increasing cell surface hydrophobicity and reducing cell surface charge, thereby mitigating cell-to-cell repulsion. Furthermore, ketoprofen induced increased levels of reactive oxygen species (ROS) production, activated the DNA damage-induced response (SOS), and enhanced cell membrane permeability, facilitating ARG transmission in intra-genus and inter-genus systems. The upregulation of outer membrane proteins, oxidative stress, SOS response, mating pair formation (Mpf) system, and DNA transfer and replication (Dtr) system related genes, as well as the inhibition of global regulatory genes, all contributed to higher transfer efficiency under ketoprofen treatment. These findings served as an early warning for a comprehensive assessment of the roles of NSAIDs in the spread of antibiotic resistance in natural aqueous environments.202439103039
850690.9997Extracellular 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
6763100.9997Sub-lethal photocatalysis promotes horizontal transfer of antibiotic resistance genes by conjugation and transformability. The spread of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in water is increasingly becoming a worldwide problem due to frequent recent major public health events. Herein, the horizontal ARG transfer mechanisms were studied under sub-lethal photocatalysis. The results show that ARGs had at most a 3- to 6-fold increase in the conjugative transfer frequency when only donor bacteria were induced with sub-lethal photocatalysis, while the frequency exhibited a trend toward inhibition when only the recipient bacteria were induced. However, when the donor or recipient bacteria were induced beforehand for a specific time, the frequency increased by a maximum of 10- to 22-fold. Moreover, the horizontal transfer frequency and its mechanism were related to the oxidative stress systems, ATP systems and the expression of related genes. Furthermore, the transformability of extracellular plasmids of the ARB and the contribution in horizontal transfer were also studied. Results show that the transformation frequency accounted for up to 50% of the total number of transconjugants, indicating that transformation might be a primary mode of horizontal ARG transfer by ARB in water. All of the above results demonstrate that sub-lethal photocatalysis will increase the frequency of horizontal gene transfer of ARGs through both conjugative transfer and the transformation pathway, which increases the risk of ARB in aquatic environments.202235841790
8607110.9997Different 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
8982120.9997Ampicillin Exposure and Glutathione Deficiency Synergistically Promote Conjugative Transfer of Plasmid-Borne Antibiotic Resistance Genes. Plasmid-mediated conjugation is an important pathway for the spread of antibiotic resistance genes (ARGs), posing a significant risk to global public health. It has been reported that the conjugative transfer of ARGs could be enhanced by oxidative stress. Whether endogenous glutathione (GSH), a major non-protein thiol compound involved in cellular redox homeostasis, influences conjugative transfer is unknown. In this study, we show that the deletion of the GSH biosynthesis gene gshA and ampicillin exposure synergistically promoted the conjugative transfer of plasmid RP4 bearing multiple ARGs from the soil bacterium Enterobacter sp. CZ-1 to Escherichia coli S17-1λπ in co-culture experiments and to diverse soil bacteria belonging to eight phyla, including some potential human pathogens, in a soil incubation experiment. The deletion of gshA increased ROS generation and cell membrane permeability, and upregulated the expression of the genes involved in intracellular oxidative stress regulation, membrane permeability, plasmid replication, and the SOS response process, especially under ampicillin exposure. These results suggest that endogenous GSH is an important factor affecting the spread of plasmid-borne ARGs. Exposure to antibiotics and environmental stresses that cause a depletion of endogenous GSH in vivo are likely to increase the risk of ARG dissemination in the environment.202540346915
8522130.9997Electrochemical disinfection may increase the spread of antibiotic resistance genes by promoting conjugal plasmid transfer. Current in the milliampere range can be used for electrochemical inactivation of bacteria. Yet, bacteria-including antibiotic resistant bacteria (ARB) may be subjected to sublethal conditions due to imperfect mixing or energy savings measures during electrochemical disinfection. It is not known whether such sublethal current intensities have the potential to stimulate plasmid transfer from ARB. In this study, conjugal transfer of plasmid pKJK5 was investigated between Pseudomonas putida strains under conditions reflecting electrochemical disinfection. Although the abundance of culturable and membrane-intact donor and recipient cells decreased with applied current (0-60 mA), both transconjugant density and transconjugant frequency increased. Both active chlorine and superoxide radicals were generated electrolytically, and ROS generation was induced. In addition, we detected significant over expression of a core oxidative stress defense gene (ahpCF) with current. Expression of selected conjugation related genes (traE, traI, trbJ, and trbL) also significantly correlated with current intensity. ROS accumulation, SOS response and subsequent derepression of conjugation are therefore the plausible consequence of sublethal current exposure. These findings suggest that sublethal intensities of current can enhance conjugal plasmid transfer, and that it is essential that conditions of electrochemical disinfection (applied voltage, current density, time and mixing) are carefully controlled to avoid conjugal ARG transmission.202336328265
6772140.9997Disinfectants facilitate the transformation of exogenous antibiotic resistance genes via multiple pathways. The prevalence and spread of multidrug-resistant (MDR) bacteria pose a global challenge to public health. Natural transformation is one of the essential ways for horizontal transfer of antibiotic resistance genes (ARGs). Although disinfectants are frequently used during COVID-19, little is known about whether these disinfectants are associated with the transformation of plasmid-borne ARGs. In our study, we assessed the effect of some disinfectants on bacterial transformation using resistance plasmids as extracellular DNA and E. coli DH5α as the recipient bacteria. The results showed that these disinfectants at environmentally relevant concentrations, including benzalkonium bromide (BB), benzalkonium chloride (BC) and polyhexamethylene guanidine hydrochloride (PHMG), significantly enhanced the transformation of plasmid-encoded ARGs. Furthermore, we investigated the mechanisms underlying the promotive effect of disinfectants on transformation. We revealed that the addition of disinfectants significantly increased the membrane permeability and promoted membrane-related genes expression. Moreover, disinfectants led to the boosted bacterial respiration, ATP production and flagellum motility, as well as increased expression of bacterial secretion system-related genes. Together, our findings shed insights into the spread of ARGs through bacterial transformation and indicate potential risks associated with the widespread use of disinfectants.202336857920
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
8503160.9997Dual-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
8981170.9997Response mechanisms of different antibiotic-resistant bacteria with different resistance action targets to the stress from photocatalytic oxidation. The stress response of antibiotic-resistant bacteria (ARB) and the spread of antibiotic resistance genes (ARGs) pose a serious threat to the aquatic environment and human beings. This study mainly explored the effect of the heterogeneous photocatalytic oxidation (UVA-TiO(2) system) on the stress response mechanism of ARB with different antibiotic resistance action targets, including the cell wall, proteins, DNA, RNA, folate and the cell membrane. Results indicate that the stress response mechanism of tetracycline- and sulfamethoxazole-resistant E. coli DH5α, which targets the synthesis of protein and folate, could rapidly induce global regulators by the overexpression of relative antibiotic resistance action target genes. Different stress response systems were mediated via cross-protection mechanism, causing stronger tolerance to an adverse environment than other ARB. Moreover, the photocatalytic inactivation mechanism of bacterial cells and a graded response of cellular stress mechanism caused differences in the intensity of the stress mechanism of antibiotic resistance action targets. E. coli DH5α resistant to cefotaxime and polymyxin, targeting synthesis of the cell wall and cell membrane, respectively, could confer greater advantages to bacterial survival and higher conjugative transfer frequency than E. coli DH5α resistant to nalidixic acid and rifampicin, which target the synthesis of DNA and RNA, respectively. This new perspective provides detailed information on the practical application of photocatalytic oxidation for inactivating ARB and hampering the spreading of ARGs in the aquatic environment.202235453030
8525180.9997Low-intensity ultrasound promotes the horizontal transfer of resistance genes mediated by plasmids in E. coli. Widespread of pathogenic bacteria resistant to antibiotics has become a worldwide public health concern. Conjugative transfer between bacteria is an important mechanism for the horizontal transfer of antibiotic resistance genes. Ultrasound has been widely applied in many fields, but the effect of ultrasound on horizontal transfer of antibiotic-resistant genes is still not clear. We discovered that low-intensity (≤ 0.05 W/cm(2)) ultrasound had no effect on bacterial growth and survival rates, but increased the permeability of cell membrane, and consequentially elevated the transfer rates of plasmid. Low-intensity  ultrasound enhanced conjugation between bacteria, induced expression of conjugation genes TrpBp and TrfAp, and inhibited expression of global regulatory genes KorA, KorB, TrbA, and TrbK. In conclusion, low-intensity ultrasound promoted horizontal transfer of antibiotic-resistant genes by enhancing conjugation and regulating expression of horizontal transfer-related genes.201829692961
8512190.9997Dissolved 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