Electrochemical disinfection may increase the spread of antibiotic resistance genes by promoting conjugal plasmid transfer. - Related Documents




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852201.0000Electrochemical 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
860410.9997Reactive 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
851320.9997Chlorine 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
852630.9997Size-dependent enhancement on conjugative transfer of antibiotic resistance genes by micro/nanoplastics. Recently micro/nanoplastics (MNPs) have raised intensive concerns due to their possible enhancement effect on the dissemination of antibiotic genes. Unfortunately, data is still lacking to verify the effect. In the study, the influence of polystyrene MNPs on the conjugative gene transfer was studied by using E. coli DH5ɑ with RP4 plasmid as the donor bacteria and E. coli K12 MG1655 as the recipient bacteria. We found that influence of MNPs on gene transfer was size-dependent. Small MNPs (10 nm in radius) caused an increase and then a decrease in gene transfer efficiency with their concentration increasing. Moderate-sized MNPs (50 nm in radius) caused an increase in gene transfer efficiency. Large MNPs (500 nm in radius) had almost no influence on gene transfer. The gene transfer could be further enhanced by optimizing mating time and mating ratio. Scavenging reactive oxygen species (ROS) production did not affect the cell membrane permeability, indicating that the increase in cell membrane permeability was not related to ROS production. The mechanism of the enhanced gene transfer efficiency was attributed to a combined effect of the increased ROS production and the increased cell membrane permeability, which ultimately regulated the expression of corresponding genes.202235278945
852440.9996Tebuconazole 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
677850.9996Bisphenol 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
852560.9996Low-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
898270.9996Ampicillin 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
677780.9996Unveiling 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
851290.9996Dissolved 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
6781100.9996Antibiotic-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
6776110.9996Natural 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
6764120.9996Chlorine 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
6763130.9996Sub-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
6771140.9996Triclosan 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
8514150.9995Graphene oxide influences transfer of plasmid-mediated antibiotic resistance genes into plants. As an emerging contaminant, antibiotic resistance genes (ARGs) are raising concerns about its significant threat to public health. Meanwhile, graphene oxide (GO), which also has a potential ecological damage with increasingly entering the environment, has a great influence on the transfer of ARGs. However, little is known about the effects mechanisms of GO on the migration of antibiotic resistance genes (ARGs) from bacteria into plants. In this study, we investigated the influence of GO on the transfer of ARGs carried by RP4 plasmids from Bacillus subtilis into rice plants. Our results showed that the presence of GO at concentrations ranging from 0 to 400 mg L(-1) significantly reduced the transfer of ARGs into rice roots by 13-71 %. Moreover, the migration of RP4 from the roots to aboveground parts was significantly impaired by GO. These effects may be attributed to several factors. First, higher GO concentrations led to low pH in the culture solution, resulting in a substantial decrease in the number of antibiotic-resistant bacteria. Second, GO induced oxidative stress in rice, as indicated by enhanced Evans blue dye staining, and elevated levels of malondialdehyde, nitric oxide, and phenylalanine ammonia-lyase activity. The oxidative stress negatively affected plant growth, as demonstrated by the reduced fresh weight and altered lignin content in the rice. Microscopic observations confirmed the entry of GO into root cells but not leaf mesophyll cells. Furthermore, potential recipients of RP4 plasmid strains in rice after co-cultivation experiments were identified, including Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus cereus. These findings clarify the influence of GO on ARGs in the bacteria-plant system and emphasize the need to consider its potential ecological risks.202437979849
8519160.9995Effects 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
6782170.9995Ubiquitous nanocolloids suppress the conjugative transfer of plasmid-mediated antibiotic resistance in aqueous environment. Nanocolloids (Nc) are widespread in natural water environment, whereas the potential effects of Nc on dissemination of antibiotic resistance remain largely unknown. In this study, Nc collected from the Yellow River in Henan province was tested for its ability to influence the conjugative transfer of resistant plasmid in aqueous environment. The results revealed that the conjugative transfer of RP4 plasmid between Escherichia coli was down-regulated by 52%-91% upon exposure to 1-10 mg/L Nc and the reduction became constant when the dose became higher (20-200 mg/L). Despite the exposure of Nc activated the anti-oxidation and SOS response in bacteria through up-regulating genes involved in glutathione biosynthesis and DNA recombination, the inhibition on the synthesis and secretion of extracellular polysaccharide induced the prevention of cell-cell contact, leading to the reduction of plasmid transfer. This was evidenced by the decreased bacterial adhesion and lowered levels of genes and metabolites relevant to transmembrane transport and D-glucose phosphorylation, as clarified in phenotypic, transcriptomics and metabolomics analysis of E. coli. The significant down-regulation of glycolysis/gluconeogenesis and TCA cycle was associated with the shortage of ATP induced by Nc. The up-regulation of global regulatory genes (korA and trbA) and the reduction of plasmid genes (trfAp, trbBp, and traG) expression also contributed to the suppressed conjugation of RP4 plasmid. The obtained findings remind that the role of ubiquitous colloidal particles is nonnegligible when practically and comprehensively assessing the risk of antibiotic resistance in the environment.202438801878
8523180.9995Tebuconazole promotes spread of a multidrug-resistant plasmid into soil bacteria to form new resistant bacterial strains. The development of antibiotic resistance threatens human and environmental health. Non-antibiotic stressors, including fungicides, may contribute to the spread of antibiotic resistance genes (ARGs). We determined the promoting effects of tebuconazole on ARG dissemination using a donor, Escherichia coli MG1655, containing a multidrug-resistant fluorescent plasmid (RP4) and a recipient (E. coli HB101). The donor was then incorporated into the soil to test whether tebuconazole could accelerate the spread of RP4 into indigenous bacteria. Tebuconazole promoted the transfer of the RP4 plasmid from the donor into the recipient via overproduction of reactive oxygen species (ROS), enhancement of cell membrane permeability and regulation of related genes. The dissemination of the RP4 plasmid from the donor to soil bacteria was significantly enhanced by tebuconazole. RP4 plasmid could be propagated into more genera of bacteria in tebuconazole-contaminated soil as the exposure time increased. These findings demonstrate that the fungicide tebuconazole promotes the spread of the RP4 plasmid into indigenous soil bacteria, revealing the potential risk of tebuconazole residues enhancing the dissemination of ARGs in soil environments.202438615769
8506190.9995Extracellular 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