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904600.9951Burkholderia pseudomallei resistance to antibiotics in biofilm-induced conditions is related to efflux pumps. Burkholderia pseudomallei, the causative agent of melioidosis, has been found to increase its resistance to antibiotics when growing as a biofilm. The resistance is related to several mechanisms. One of the possible mechanisms is the efflux pump. Using bioinformatics analysis, it was found that BPSL1661, BPSL1664 and BPSL1665 were orthologous genes of the efflux transporter encoding genes for biofilm-related antibiotic resistance, PA1874-PA1877 genes in Pseudomonas aeruginosa strain PAO1. Expression of selected encoding genes for the efflux transporter system during biofilm formation were investigated. Real-time reverse transcriptase PCR expression of amrB, cytoplasmic membrane protein of AmrAB-OprA efflux transporter encoding gene, was slightly increased, while BPSL1665 was significantly increased during growth of bacteria in biofilm formation. Minimum biofilm inhibition concentration and minimum biofilm eradication concentration (MBEC) of ceftazidime (CTZ), doxycycline (DOX) and imipenem were found to be 2- to 1024-times increased when compared to their MICs for of planktonic cells. Inhibition of the efflux transporter by adding phenylalanine arginine β-napthylamide (PAβN), a universal efflux inhibitor, decreased 2 to 16 times as much as MBEC in B. pseudomallei biofilms with CTZ and DOX. When the intracellular accumulation of antibiotics was tested to reveal the pump inhibition, only the concentrations of CTZ and DOX increased in PAβN treated biofilm. Taken together, these results indicated that BPSL1665, a putative precursor of the efflux pump gene, might be related to the adaptation of B. pseudomallei in biofilm conditions. Inhibition of efflux pumps may lead to a decrease of resistance to CTZ and DOX in biofilm cells.201627702426
783210.9951Reduction of antibiotics and antibiotic resistance genes in simulated-sunlight-supported counter-diffusion bacteria-Algae biofilms: Interface properties and functional gene responses. A novel bacteria-algae symbiotic counter-diffusion biofilm system integrated within simulated-sunlight (designated UV-MABAR) was engineered to simultaneously address antibiotic residuals and antibiotic resistance genes (ARGs) while maintaining functional microbial consortia under simulated solar irradiation. The non-algal control system (UV-MABR) demonstrated elevated repulsion energy barriers accompanied by significant suppression of ATP synthase (p < 0.01) and DNA repair-related gene clusters, leading to biofilm homeostasis disruption and subsequent sulfamethoxazole (SMX) effluent accumulation peaking at 138.11±2.34 μg/L. In contrast, the UV-MABAR configuration exhibited dynamic quenching of tyrosine-associated fluorescence moieties within extracellular polymeric substances, thereby diminishing complexation potential with SMX aromatic rings and achieving 70.75 %±3.21 % abiotic photodegradation efficiency, which substantially curtailed ARG proliferation pathways, promoting a significant downregulation of sul1 (-1.9 log(2) fold-change) and sul2 (-1.1 log(2) fold-change) expression compared to conventional MABR controls. Besides, algal in UV-MABAR attenuated the irradiation-induced α-helix/(β-sheet + random coil) conformational shift, moderating biofilm matrix compaction. Crucially, algal proliferation up-regulated bacterial recA expression (1.7-fold increase), thereby preserving catabolic gene integrity and preventing endogenous substances release. These protective measures kept effluent concentrations of SMX, NH(4)(+)-N, total nitrogen, and COD in UV-MABAR at 19.84 μg/L, 3.88 mg/L, 12.76 mg/L, and 34.97 mg/L, respectively, during 150 days of operation.202540738088
786020.9950Enhanced removal of antibiotic-resistant bacteria and resistance genes by three-dimensional electrochemical process using MgFe(2)O(4)-loaded biochar as both particle electrode and catalyst for peroxymonosulfate activation. In this study, MgFe(2)O(4)-loaded biochar (MFBC) was used as a three-dimensional particle electrode to active peroxymonosulfate (EC/MFBC/PMS) for the removal of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). The results demonstrated that, under the conditions of 1.0 mM PMS concentration, 0.4 g/L material dosage, 5 V voltage intensity, and MFBC preparation temperature of 600 °C, the EC/MFBC600/PMS system achieved complete inactivation of E. coli DH5α within 5 min and the intracellular sul1 was reduced by 81.5 % after 30 min of the treatment. Compared to EC and PMS alone treatments, the conjugation transfer frequency of sul1 rapidly declined by 92.9 % within 2 min. The cell membrane, proteins, lipids, as well as intracellular and extracellular ARGs in E. coli DH5α were severely damaged by free radicals in solution and intracellular reactive oxygen species (ROS). Furthermore, up-regulation was observed in genes associated with oxidative stress, SOS response and cell membrane permeability in E. coli DH5α, however, no significant changes were observed in functional genes related to gene conjugation and transfer mechanisms. This study would contribute to the underlying of PMS activation by three-dimensional particle electrode, and provide novel insights into the mechanism of ARB inactivation and ARGs degradation under PMS advanced oxidation treatment.202439197284
849130.9950Hormesis-like effects of black phosphorus nanosheets on the spread of multiple antibiotic resistance genes. The production scalability and increasing demand for black phosphorus nanosheets (BPNSs) inevitably lead to environmental leakage. Although BPNSs' ecotoxicological effects have been demonstrated, their indirect health risks, such as inducing increased resistance in pathogenic bacteria, are often overlooked. This study explores the influence of BPNSs on the horizontal gene transfer of antibiotic resistance genes (ARGs) facilitated by the RP4 plasmid, which carries multiple resistance genes. The results indicated that BPNSs exhibited concentration-dependent hormesis-like effects on bacterial conjugation gene transfer. Specifically, at sub-inhibitory concentrations (0.0001-1 mg/L), BPNSs promoted both intra- and intergeneric conjugative transfer, demonstrating an initial increase followed by a decline, with transfer rates rising by 1.5-3.1-fold and 1.5-3.3-fold, respectively. BPNSs were found to induce reactive oxygen species (ROS) production, increase malondialdehyde levels, and trigger the SOS response, enhancing plasmid uptake. Additionally, BPNSs increased membrane permeability by forming pores and upregulating outer membrane porins (OMPs) genes. At higher BPNSs concentrations (0.1-1 mg/L), conjugative frequency was inhibited due to the disruption of the cellular antioxidant system and changes in the adsorption process. These findings underscore the influence of BPNSs on the conjugative transfer of ARGs, complementing current knowledge of the biotoxicity and potential ecological risks associated with BPNSs.202539827804
34240.9950Heat-shock-increased survival to far-UV radiation in Escherichia coli is wavelength dependent. Heat-shock-induced resistance to far-UV (FUV) radiation was studied in Escherichia coli. The induction of FUV resistance was shown to be dependent on the products of the genes uvrA and polA in bacteria irradiated at 254 nm. Heat shock increased the resistance to 280 nm radiation in a uvrA6 recA13 mutant. Heat shock lowered the mutation frequency (reversion to tryptophan proficiency) in wild-type or uvrA strains irradiated at 254 nm. When these strains were irradiated at 280 nm, heat shock did not interfere with the mutation frequency in the wild-type strain, but greatly enhanced mutations in the uvrA mutant. After heat-shock treatment, the wild-type strain irradiated at 254 nm showed increased DNA degradation, indicating enhanced repair activity. However, heat shock did not stimulate SOS repair triggered by FUV. An increased survival of bacteriophages irradiated with FUV and inoculated into heat-shock-treated bacteria was not detected. The possibility that heat shock enhances excision repair activity in a wavelength-dependent manner is discussed.19948176549
904550.9948Development of Resistance in Escherichia coli ATCC25922 under Exposure of Sub-Inhibitory Concentration of Olaquindox. Quinoxaline1,4-di-N-oxides (QdNOs) are a class of important antibacterial drugs of veterinary use, of which the drug resistance mechanism has not yet been clearly explained. This study investigated the molecular mechanism of development of resistance in Escherichia coli (E. coli) under the pressure of sub-inhibitory concentration (sub-MIC) of olaquindox (OLA), a representative QdNOs drug. In vitro challenge of E. coli with 1/100× MIC to 1/2× MIC of OLA showed that the bacteria needed a longer time to develop resistance and could only achieve low to moderate levels of resistance as well as form weak biofilms. The transcriptomic and genomic profiles of the resistant E. coli induced by sub-MIC of OLA demonstrated that genes involved in tricarboxylic acid cycle, oxidation-reduction process, biofilm formation, and efflux pumps were up-regulated, while genes involved in DNA repair and outer membrane porin were down-regulated. Mutation rates were significantly increased in the sub-MIC OLA-treated bacteria and the mutated genes were mainly involved in the oxidation-reduction process, DNA repair, and replication. The SNPs were found in degQ, ks71A, vgrG, bigA, cusA, and DR76(-)4702 genes, which were covered in both transcriptomic and genomic profiles. This study provides new insights into the resistance mechanism of QdNOs and increases the current data pertaining to the development of bacterial resistance under the stress of antibacterials at sub-MIC concentrations.202033182563
848960.9948Signaling molecules accelerate the transmission of antibiotic resistance genes under the stress of copper. Heavy metals can accelerate the dissemination of antibiotic resistance genes (ARGs) in aquatic environments by imposing environmental stresses. Signaling molecules play a role in bacterial communication and help bacteria adapt to environmental stresses. However, little is known whether the presence of signaling molecules has an effect on the spread of ARGs induced by heavy metals. In this study, we investigated how N-decanoyl-L-homoserine lactone (C10-HSL) affects copper-induced conjugative transfer of ARGs. We calculated the conjugative transfer frequency and measured reactive oxygen species (ROS) production, membrane permeability, and the expression of relevant genes. The results demonstrated that the addition of C10-HSL increased the conjugative transfer frequency of ARGs under copper ions (Cu(2+)) stress, showing a 7.2-fold increase under 0.5 μM Cu(2+) and 0.39 μM C10-HSL treatment compared to the control. This enhancement was associated with elevated intracellular ROS production and increased membrane permeability. The reduced conjugative transfer frequency under anaerobic conditions or with thiourea treatment supported the key role of ROS in this process. Furthermore, ROS overproduction triggered the SOS response, as evidenced by a 9-fold upregulation of recA expression. C10-HSL also modulated membrane-associated gene expression by upregulating outer membrane porins and downregulating efflux pump genes under Cu(2+)stress. This study provides a new insight into the spread of ARGs in aquatic environments.202540840413
619070.9947Identifying Escherichia coli genes involved in intrinsic multidrug resistance. Multidrug resistance is a major cause of clinical failure in treating bacterial infections. Increasing evidence suggests that bacteria can resist multiple antibiotics through intrinsic mechanisms that rely on gene products such as efflux pumps that expel antibiotics and special membrane proteins that block the penetration of drug molecules. In this study, Escherichia coli was used as a model system to explore the genetic basis of intrinsic multidrug resistance. A random mutant library was constructed in E. coli EC100 using transposon mutagenesis. The library was screened by growth measurement to identify the mutants with enhanced or reduced resistance to chloramphenicol (Cm). Out of the 4,000 mutants screened, six mutants were found to be more sensitive to Cm and seven were more resistant compared to the wild-type EC100. Mutations in 12 out of the 13 mutants were identified by inverse polymerase chain reaction. Mutants of the genes rob, garP, bipA, insK, and yhhX were more sensitive to Cm compared to the wild-type EC100, while the mutation of rhaB, yejM, dsdX, nagA, yccE, atpF, or htrB led to higher resistance. Overexpression of rob was found to increase the resistance of E. coli biofilms to tobramycin (Tob) by 2.7-fold, while overexpression of nagA, rhaB, and yccE significantly enhanced the susceptibility of biofilms by 2.2-, 2.5-, and 2.1-fold respectively.200818807027
786280.9946Synergistic effect of sulfidated nanoscale zerovalent iron in donor and recipient bacterial inactivation and gene conjugative transfer inhibition. Antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) are widespread in urban wastewater treatment plants (UWTPs). In this research, a horizontal transfer model of recipient (Pseudomonas. HLS-6) and donor (Escherichia coli DH5α carries RP4 plasmid) was constructed to explore the effect of sulfidated nanoscale zerovalent iron (S-nZVI) on the efficiency of plasmid-mediated horizontal transfer. When the S/Fe was 0.1, the inactivation efficiency of 1120 mg/L S-nZVI on the donor and recipient bacteria were 2.36 ± 0.03 log and 3.50 ± 0.17 log after 30 min, respectively (initial ARB concentration ≈ 5 ×10(7) CFU/mL). Effects of treatment time, S/Fe molar ratio, S-nZVI dosage and initial bacterial concentration were systemically studied. S-nZVI treatment could increase the extracellular alkaline phosphatase and malondialdehyde content of the ARB, cause oxidative stress in the bacteria, destroy the cell structure and damage the intracellular DNA. This study provided evidence and insights into possible underlying mechanisms for reducing conjugative transfer, such as hindering cell membrane repair, inducing the overproduction of reactive oxygen species, inhibiting the SOS response, reducing the expression of ARGs and related transfer genes. S-nZVI could inhibit the gene conjugative transfer while inactivating the ARB. The findings provided an alternative method for controlling antibiotic resistance.202235334272
848890.9946Antihistamine drug loratadine at environmentally relevant concentrations promotes conjugative transfer of antibiotic resistance genes: Coeffect of oxidative stress and ion transport. Due to the widespread use of loratadine (LOR) as an antihistamine, it is widely distributed in the environment as an emerging contaminant. However, its impact on the dissemination of antibiotic resistance genes (ARGs) remains unclear. This study investigated the effect of LOR on the conjugative transfer of ARGs and elucidated the potential mechanisms through transcriptome analysis. The results showed that LOR significantly promoted the frequency of conjugative transfer up to 1.5- to 8.6-fold higher compared with the control group. Exposure to LOR increased reactive oxidative species (ROS) and intracellular Ca(2+) concentrations, leading to the upregulation of expression of genes related to transmembrane transport and SOS response. Meanwhile, it stimulated the increase of cell membrane permeability. Moreover, LOR exposure could enhance H(+) efflux in donor bacteria, resulting in the decrease of intracellular pH and the elevation of transmembrane potential, which could induce the increase of ion transport, thereby promoting plasmid efflux from the cell membrane. Based on this, we inferred that LOR can induce an increase in ROS level and intracellular Ca(2+) concentrations, and promoted the efflux of intracellular H(+). This, in turn, triggered the intensification of various ion transport processes on the cell membrane, thereby increasing membrane permeability and accelerating plasmid efflux. Ultimately, the coeffect of oxidative stress response and ion transport promoted conjugative transfer. This study demonstrated that LOR significantly promotes plasmid-mediated conjugative transfer of ARGs, providing novel insights into the mechanisms underlying this process.202539919578
7867100.9946The removal of antibiotic resistant bacteria and antibiotic resistance genes by sulfidated nanoscale zero-valent iron activating periodate: Efficacy and mechanism. Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have drawn much more attention due to their high risk on human health and ecosystem. In this study, the performance of sulfidated nanoscale zero-valent iron (S-nZVI)/periodate (PI) system toward ARB inactivation and ARGs removal was systematically investigated. The S-nZVI/PI system could realize the complete inactivation of 1 × 10(8) CFU/mL kanamycin, ampicillin, and tetracycline-resistant E. coli HB101 within 40 min, meanwhile, possessed the ability to remove the intracellular ARGs (iARGs) (including aphA, tetA, and tnpA) carried by E. coli HB101. Specifically, the removal of aphA, tetA, and tnpA by S-nZVI/PI system after 40 min reaction was 0.31, 0.47, and 0.39 log(10)copies/mL, respectively. The reactive species attributed to the E. coli HB101 inactivation were HO(•) and O(2)(•-), which could cause the destruction of E. coli HB101 morphology and enzyme system (such as superoxide dismutase and catalase), the loss of intracellular substances, and the damage of iARGs. Moreover, the influence of the dosage of PI and S-nZVI, the initial concentration of E. coli HB101, as well as the co-existing substance (such as HCO(3)(-), NO(3)(-), and humic acid (HA)) on the inactivation of E. coli HB101 and its corresponding iARGs removal was also conducted. It was found that the high dosage of PI and S-nZVI and the low concentration of E. coli HB101 could enhance the disinfection performance of S-nZVI/PI system. The presence of HCO(3)(-), NO(3)(-), and HA in S-nZVI/PI system showed inhibiting role on the inactivation of E. coli HB101 and its corresponding iARGs removal. Overall, this study demonstrates the superiority of S-nZVI/PI system toward ARB inactivation and ARGs removal.202337544470
8495110.9946Effects of voltage and tetracycline on horizontal transfer of ARGs in microbial electrolysis cells. The abuse of antibiotics leads to the production of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Microbial electrolysis cells (MECs) have been widely applicated in the field of degrading antibiotics. ARGs were increased via horizontal transfer in single and two-chamber MECs. As one of the critical parameters in MECs, voltage has a particular impact on the ARGs transfer via horizontal transfer. However, there have been few studies of ARGs transfer under the exposure of antibiotics and voltage in MECs. In this study, five concentrations of tetracycline (0, 1, 5, 10, 20 mg/L) were selected to explore the conjugative transfer frequency of plasmid-encoded the ARGs from the donor (E. coli RP4) to receptor (E. coli HB101) in MECs, two voltages (1.5 and 2.0 V) were used to explore the conjugative transfer frequency of ARGs in MECs, then, the transfer of ARGs in MECs under the co-effect of tetracycline and voltage was explored. The results showed that the conjugative transfer frequency of ARGs was significantly increased with the increase of tetracycline concentration and voltage, respectively (p < 0.05). Under the pressure of tetracycline and voltage, the conjugative transfer frequency of ARGs is significantly enhanced with the co-effect of tetracycline and voltage (p < 0.05). The oxidative response induced by electrical stimulation promotes the overproduction of reactive oxygen species and the enhancement of cell membrane permeability of donor and recipient bacteria in MECs. These findings provide insights for studying the spread of ARGs in MECs.202435980276
8818120.9946Metatranscriptomic analysis of adaptive response of anammox bacteria Candidatus 'Kuenenia stuttgartiensis' to Zn(II) exposure. Zn(II) is frequently detected in biological nitrogen removal systems treating high-strength wastewater (e.g., landfill leachate), yet the cellular defense strategies of anammox bacteria against Zn(II) cytotoxicity is largely unknown. To uncover survival mechanisms under Zn(II) stress, responses of enriched anammox bacteria Candidatus 'Kuenenia stuttgartiensis' under exposure of various levels of Zn (II) were investigated through metatranscriptomic sequencing. Although increasing Zn(II) levels (50, 100 and 150 mg/L) resulted in decreasing anammox activities (86.1 ± 0.8%, 66.1 ± 1.4% and 43.9 ± 1.5% of the control, respectively), the viable cells in anammox sludge remained stable. Candidatus 'K. stuttgartiensis' possesses a complex network of regulatory systems to confer cells with the ability against Zn(II) toxicity, including functions related to substrate degradation, Zn(II) efflux, chelation, DNA repair, protein degradation, protein synthesis and signal transduction processes. Particularly, in order to maintain Zn(II) homeostasis, Candidatus 'K. stuttgartiensis' upregulated genes encoding RND efflux family (czcA, czcB, czcC, kustd1923 and kuste2279) for exporting Zn(II) actively. These heavy metal exporting genes could act as "sentinel genes" to detect the initial stage of Zn(II) inhibition on anammox bacteria, which might be beneficial to develop a diagnostic approach to predict the risk of operational failure when Zn(II) shock occurs.202031901527
8492130.9945Promotion effects and mechanisms of molybdenum disulfide on the propagation of antibiotic resistance genes in soil. The rapid development of nanotechnology has aroused considerable attentions toward understanding the effects of engineered nanomaterials (ENMs) on the propagation of antibiotic resistance. Molybdenum disulfide (MoS(2)) is an extensively used ENM and poses potential risks associated with environmental exposure; nevertheless, the role of MoS(2) toward antibiotic resistance genes (ARGs) transfer remains largely unknown. Herein, it was discovered that MoS(2) nanosheets accelerated the horizontal transfer of RP4 plasmid across Escherichia coli in a dose-dependent manner (0.5-10 mg/L), with the maximum transfer frequency 2.07-fold higher than that of the control. Integration of physiological, transcriptomics, and metabolomics analyses demonstrated that SOS response in bacteria was activated by MoS(2) due to the elevation of oxidative damage, accompanied by cell membrane permeabilization. MoS(2) promoted bacterial adhesion and intercellular contact via stimulating the secretion of extracellular polysaccharides. The ATP levels were maximally increased by 305.7 % upon exposure to MoS(2), and the expression of plasmid transfer genes was up-regulated, contributing to the accelerated plasmid conjugation and increased ARG abundance in soil. Our findings highlight the roles of emerging ENMs (e.g., MoS(2)) in ARGs dissemination, which is significant for the safe applications and risk management of ENMs under the development scenarios of nanotechnology.202337062264
8530140.9945Intrinsic chlorine resistance of bacteria modulated by glutaminyl-tRNA biosynthesis in drinking water supply systems. The existence of chlorine-resistant bacteria (CRB) in drinking water supply systems (DWSSs) results in significant challenges to the biological security of drinking water. However, little is known about the intrinsic chlorine-resistant molecular metabolic mechanism of bacteria in DWSSs. This research explored the microbial interactions and the key metabolic pathways that modulate the chlorine resistance of bacteria in full-scale chloraminated DWSSs. The dominant CRB, including Bdellovibrio, Bradyrhizobium, Peredibacter, Sphingomonas, and Hydrogenophaga, strongly interacted with each other to maintain basic metabolism. A total of 4.21% of the bacterial metabolic pathways were key and specific to chlorine-resistant bacteria. Glutaminyl-tRNA biosynthesis was the dominant metabolic pathway of CRB in the target DWSSs. After chloramine disinfection, the relative abundance of glutamate-tRNA ligase (GlnRS) and the related orthologous genes increased by 10.11% and 14.58%, respectively. The inactivation rate of the GlnRS overexpression strain (81.40%) was lower than that of the wild-type strain (90.11%) after exposure to chloramine. Meanwhile, the growth rate of the GlnRS overexpression strain was higher than that of the wild-type strain. Glutaminyl-tRNA biosynthesis can enhance chlorine resistance in DWSSs.202236084827
8819150.9945Responses of Bacillus sp. under Cu(II) stress in relation to extracellular polymeric substances and functional gene expression level. The production and composition of extracellular polymeric substances (EPS), as well as the EPS-related functional resistance genes and metabolic levels of Bacillus sp. under Cu(II) stress, were investigated. EPS production increased by 2.73 ± 0.29 times compared to the control when the strain was treated with 30 mg L(-1) Cu(II). Specifically, the polysaccharide (PS) content in EPS increased by 2.26 ± 0.28 g CDW(-1) and the PN/PS (protein/polysaccharide) ratio value increased by 3.18 ± 0.33 times under 30 mg L(-1) Cu(II) compared to the control. The increased EPS secretion and higher PN/PS ratio in EPS strengthened the cells' ability to resist the toxic effect of Cu(II). Differential expression of functional genes under Cu(II) stress was revealed by Gene Ontology pathway enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. The enriched genes were most obviously upregulated in the UMP biosynthesis pathway, the pyrimidine metabolism pathway, and the TCS metabolism pathway. This indicates an enhancement of EPS regulation-related metabolic levels and their role as a defense mechanism for cells to adapt to Cu(II) stress. Additionally, seven copper resistance genes were upregulated while three were downregulated. The upregulated genes were related to the heavy metal resistance, while downregulated genes were related to cell differentiation, indicating that the strain had initiated an obvious resistance to Cu(II) despite its severe cell toxicity. These results provided a basis for promoting EPS-regulated associated functional genes and the application of gene-regulated bacteria in heavy metal-containing wastewater treatment.202337195605
6351160.9945Heterogeneous expression of DnaK gene from Alicyclobacillus acidoterrestris improves the resistance of Escherichia coli against heat and acid stress. Alicyclobacillus acidoterrestris, an acidophilic and thermophilic bacteria, is an important microbial resource for stress resistance genes screening. In this study, DnaK gene from A. acidoterrestris was subcloned to construct the recombinant plasmid pET28a-DnaK. The successful construction of the plasmid was verified by double-enzyme digestion and sequencing analysis. The recombinant plasmid was transformed into Escherichia coli BL21 and isopropy-β-D-thiogalactoside (IPTG) was used to induce recombinant E. coli to express DnaK gene. A 70 kD fusion protein was identified by SDS-PAGE, which suggested that DnaK gene from A. acidoterrestris was successfully expressed. The recombinant and wild BL21 were treated with high temperatures of 54, 56 and 58 °C at pH values of 5.0-7.0 to compare the effects of heterogeneous expression of the DnaK gene from A. acidoterrestris on the stress resistance. The experimental results showed that survival rate of recombinant BL21-DnaK has been improved considerably under heat and acid stresses in contrast with the wild BL21, and D-values of recombinant BL21 were 14.7-72% higher than that of wild BL21, which demonstrated that heterogeneous expression of DnaK gene from A. acidoterrestris could significantly enhance the resistance of host bacteria E. coli against heat and acid stresses.201728194744
7865170.9945Inactivation of antibiotic resistant bacteria by Fe(3)O(4) @MoS(2) activated persulfate and control of antibiotic resistance dissemination risk. Antibiotic resistance poses a global environmental challenge that jeopardizes human health and ecosystem stability. Antibiotic resistant bacteria (ARB) significantly promote the spreading and diffusion of antibiotic resistance. This study investigated the efficiency and mechanism of inactivating tetracycline-resistant Escherichia coli (TR E. coli) using Fe(3)O(4) @MoS(2) activated persulfate (Fe(3)O(4) @MoS(2)/PS). Under optimized conditions (200 mg/L Fe(3)O(4) @MoS(2), 4 mM PS, 35 °C), TR E. coli (∼7.5 log CFU/mL) could be fully inactivated within 20 min. The primary reactive oxygen species (ROS) responsible for TR E. coli inactivation in the Fe(3)O(4) @MoS(2)/PS system were hydroxyl radicals (•OH) and superoxide radicals (•O(2)(-)). Remarkably, the efflux pump protein was targeted and damaged by the generated ROS during the inactivation process, resulting in cell membrane rupture and efflux of cell content. Additionally, the horizontal transmission ability of residual antibiotic resistance genes (ARGs) harboring in the TR E. coli was also reduced after the inactivation treatment. This study offers an efficient approach for TR E. coli inactivation and substantial mitigation of antibiotic resistance dissemination risk.202438286046
8521180.9945Natural organic matters promoted conjugative transfer of antibiotic resistance genes: Underlying mechanisms and model prediction. Dissemination of antibiotic resistance gene (ARG) is a huge challenge around the world. Natural organic matter (NOM) is one of the most commonly components in aquatic systems. Information regarding ARG transfer induced by NOM is still lacking. In this study, experimental exploration and model prediction on RP4 plasmid conjugative transfer between bacteria under NOM exposure was conducted. Compared with no exposure, the conjugative transfer frequency of RP4 plasmid increased 7.1-fold and 3.2-fold under exposure to 10 kDa and 100 kDa NOM exposure, respectively. NOM exposure with a lower molecular weight and higher concentration promoted gene expressions related to reactive oxygen species generation, cell membrane permeability, intercellular contact, quorum sensing, and energy driving force. Concurrently, the expressions of conjugation genes in RP4 plasmid were also upregulated. Moreover, model prediction demonstrated that the maintenance of the acquired plasmid was shortened to 133 h under 10 kDa NOM exposure compared with the control (200 h). Long-term NOM exposure enhanced transfer frequency and transfer rate of ARG. This study firstly theoretically and experimentally revealed the underlying mechanisms for promoting ARG transfer by NOM.202236436463
6375190.9944Role of ppGpp-regulated efflux genes in Acinetobacter baumannii. OBJECTIVES: Treatment of infections caused by Acinetobacter baumannii nosocomial strains has become increasingly problematic owing to their resistance to antibiotics. ppGpp is a secondary messenger involved in growth control and various stress responses in bacteria. The mechanism for inhibition of antibiotic resistance via ppGpp is still unidentified in various pathogenic bacteria including A. baumannii. Here, we investigated the effects of ppGpp on efflux pump (EP)-related genes in A. baumannii. METHODS: ppGpp-deficient and -complementary strains were constructed by conjugation and we confirmed (p)ppGpp measurements by thin-layer chromatography. We observed that the ppGpp-deficient strain (ΔA1S_0579) showed abnormal stretching patterns by transmission electron microscopy analysis. The MICs of antimicrobial agents for the WT A. baumannii (ATCC 17978), ppGpp-deficient and complementary strains were determined by the Etest and broth dilution assay methods. The expression levels of EP-related genes were determined by quantitative RT-PCR. RESULTS: We observed morphological differences between a ppGpp-deficient strain (ΔA1S_0579) and the WT strain. Dramatic reductions of MICs in the ppGpp-deficient strain compared with the WT were observed for gentamicin (2.6-fold), tetracycline (3.9-fold), erythromycin (4-fold) and trimethoprim (>4-fold). Expression of the EP-related genes abeB (2.8-fold), tet(A) (2.3-fold), adeB (10.0-fold), adeI (9.9-fold), adeJ (11.8-fold) and adeK (14.4-fold) was also decreased in the ppGpp-deficient strain. CONCLUSIONS: This study demonstrates that ppGpp regulates EP-related gene expression in A. baumannii, affecting antibiotic susceptibility. To date, treatment for MDR A. baumannii has had no new antimicrobial agents, so the A1S_0579 gene could be a novel therapeutic target for rational drug design by affecting ppGpp production.202032049284