# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 8522 | 0 | 0.9981 | Electrochemical 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. | 2023 | 36328265 |
| 8604 | 1 | 0.9979 | Reactive 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. | 2025 | 40505407 |
| 315 | 2 | 0.9979 | Phosphorothioate DNA as an antioxidant in bacteria. Diverse bacteria contain DNA with sulfur incorporated stereo-specifically into their DNA backbone at specific sequences (phosphorothioation). We found that in vitro oxidation of phosphorothioate (PT) DNA by hydrogen peroxide (H(2)O(2)) or peracetic acid has two possible outcomes: DNA backbone cleavage or sulfur removal resulting in restoration of normal DNA backbone. The physiological relevance of this redox reaction was investigated by challenging PT DNA hosting Salmonella enterica cells using H(2)O(2). DNA phosphorothioation was found to correlate with increasing resistance to the growth inhibition by H(2)O(2). Resistance to H(2)O(2) was abolished when each of the three dnd genes, required for phosphorothioation, was inactivated. In vivo, PT DNA is more resistant to the double-strand break damage caused by H(2)O(2) than PT-free DNA. Furthermore, sulfur on the modified DNA was consumed and the DNA was converted to PT-free state when the bacteria were incubated with H(2)O(2). These findings are consistent with a hypothesis that phosphorothioation modification endows DNA with reducing chemical property, which protects the hosting bacteria against peroxide, explaining why this modification is maintained by diverse bacteria. | 2012 | 22772986 |
| 8813 | 3 | 0.9978 | Enhancing Escherichia coli abiotic stress resistance through ornithine lipid formation. Escherichia coli is a common host for biotechnology and synthetic biology applications. During growth and fermentation, the microbes are often exposed to stress conditions, such as variations in pH or solvent concentrations. Bacterial membranes play a key role in response to abiotic stresses. Ornithine lipids (OLs) are a group of membrane lipids whose presence and synthesis have been related to stress resistance in bacteria. We wondered if this stress resistance could be transferred to bacteria not encoding the capacity to form OLs in their genome, such as E. coli. In this study, we engineered different E. coli strains to produce unmodified OLs and hydroxylated OLs by expressing the synthetic operon olsFC. Our results showed that OL formation improved pH resistance and increased biomass under phosphate limitation. Transcriptome analysis revealed that OL-forming strains differentially expressed stress- and membrane-related genes. OL-producing strains also showed better growth in the presence of the ionophore carbonyl cyanide 3-chlorophenylhydrazone (CCCP), suggesting reduced proton leakiness in OL-producing strains. Furthermore, our engineered strains showed improved heterologous violacein production at phosphate limitation and also at low pH. Overall, this study demonstrates the potential of engineering the E. coli membrane composition for constructing robust hosts with an increased abiotic stress resistance for biotechnology and synthetic biology applications. KEY POINTS: • Ornithine lipid production in E. coli increases biomass yield under phosphate limitation. • Engineered strains show an enhanced production phenotype under low pH stress. • Transcriptome analysis and CCCP experiments revealed reduced proton leakage. | 2024 | 38587638 |
| 8600 | 4 | 0.9978 | Does the herbicide napropamide exhibit enantioselective effects across genus plasmid transfer from Escherichia coli to Bacillus subtilis? The dissemination of plasmid-borne antibiotic resistance genes (ARGs) into the environment is an urgent concern. However, the enantioselective effects of herbicides on plasmid conjugation among bacterial genera and their underlying mechanisms remain unclear. This study demonstrates for the first time that the herbicide napropamide (NAP), commonly used in vegetable fields, exhibits a concentration-dependent effect on the transfer efficiency of the pBE2R plasmid from Escherichia coli to Bacillus subtilis. Notably, at a concentration of 5 mg L(-1), R-NAP increased transfer efficiency by threefold compared to the S-enantiomer. Scanning electron microscopy revealed that R-NAP caused less structural damage to bacteria than S-NAP but more effectively reduced cell wall components (lipopolysaccharides and peptidoglycan) in donor and recipient bacteria, increasing reactive oxygen species levels and membrane permeability. Transcriptomic analysis indicated that NAP enantiomers altered the expression of genes related to membrane transport activity and transposons. Cross-domain network analysis identified yieK, ygeH, and ydbL as key genes mediating conjugation transfer. Molecular docking results showed that NAP likely interacts hydrophobically with the active sites of the proteins encoded by these genes. In conclusion, herbicides like R-NAP should be carefully managed in fields irrigated with livestock manure to mitigate the risk of ARG transfer and accumulation in crops. | 2025 | 39637801 |
| 8487 | 5 | 0.9978 | Mechanisms of nano zero-valent iron in enhancing dibenzofuran degradation by a Rhodococcus sp.: Trade-offs between ATP production and protection against reactive oxygen species. Nano zero-valent iron (nZVI) can enhance pollutants biodegradation, but it displays toxicity towards microorganisms. Gram-positive (G(+)) bacteria exhibit greater resistance to nZVI than Gram-negative bacteria. However, mechanisms of nZVI accelerating pollutants degradation by G(+) bacteria remain unclear. Herein, we explored effects of nZVI on a G(+) bacterium, Rhodococcus sp. strain p52, and mechanisms by which nZVI accelerates biodegradation of dibenzofuran, a typical polycyclic aromatic compound. Electron microscopy and energy dispersive spectroscopy analysis revealed that nZVI could penetrate cell membranes, which caused damage and growth inhibition. nZVI promoted dibenzofuran biodegradation at certain concentrations, while higher concentration functioned later due to the delayed reactive oxygen species (ROS) mitigation. Transcriptomic analysis revealed that cells adopted response mechanisms to handle the elevated ROS induced by nZVI. ATP production was enhanced by accelerated dibenzofuran degradation, providing energy for protein synthesis related to antioxidant stress and damage repair. Meanwhile, electron transport chain (ETC) was adjusted to mitigate ROS accumulation, which involved downregulating expression of ETC complex I-related genes, as well as upregulating expression of the genes for the ROS-scavenging cytochrome bd complex and ETC complex II. These findings revealed the mechanisms underlying nZVI-enhanced biodegradation by G(+) bacteria, offering insights into optimizing bioremediation strategies involving nZVI. | 2025 | 39549579 |
| 8907 | 6 | 0.9978 | Development of bacterial resistance induced by low concentration of two-dimensional black phosphorus via mutagenesis. The wide use of nano-antibacterial materials has triggered concerns over the development of nanomaterials-associated bacterial resistance. Two-dimensional (2D) black phosphorus (BP) as a new class of emerging 2D nanomaterial has displayed excellent antibacterial performance. However, whether bacteria repeatedly exposed to 2D BP can develop resistance is not clear. We found that wild type E. coli K-12 MG 1655 strains can increase resistance to 2D-BP nanosheets after repeated exposure with subinhibitory concentration of 2D-BP nanosheets. Adaptive morphogenesis including the reinforced barrier function of cell membrane were observed in the resistant bacteria, which enhanced the resistance of bacteria to 2D-BP nanosheets. The whole-genome sequencing analysis showed that the three mutation genes including dmdA, mntP, and gyrA genes were observed in the 2D-BP resistant strains, which controlled catabolism, membrane structure, and DNA replication, respectively. Furthermore, transcriptional sequencing confirmed that these genes related to metabolization, membrane structure, and cell motility were upregulated in the 2D-BP resistant bacteria. The development of resistance to 2D-BP in bacteria mainly attributed to the changes in energy metabolism and membrane structure of bacteria caused by gene mutations. In addition, the up-regulated function of cell motility also helped the bacteria to develop resistance by escaping external stimuli. The results provided new evidence for understanding an important effect of nano-antibacterial materials on the development of bacterial resistance. | 2022 | 35733674 |
| 8976 | 7 | 0.9978 | Biosynthesis of H(2)S and Siderophores Targeting Gram-Negative Bacterial Resistance to Reactive Oxygen Species. Reactive oxygen species (ROS) are a promising alternative bactericide. However, it is questioned that bacteria can potentially develop resistance to ROS, similar to their resistance against antibiotics and silver. Herein, it is reported that Gram-negative bacteria, including Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae, develop resistance to ROS after six repeated exposures. Notably, ROS minimum inhibitory concentration of Pseudomonas aeruginosa significantly increases to 256-fold after ten passages. The resistance mechanism predominantly originates from the intensified biosynthesis of the highly reductive hydrogen sulfide (H(2)S) and pyoverdine (PVD) siderophores, effectively neutralizing ROS. Simultaneously, PVD transports Fe(3+) from the extracellular space into the bacteria, releasing H(2)S bound to Fe(3+) and enhancing ROS scavenging. Additionally, the enhanced outer membrane (OM) biogenesis establishes a robust OM barrier, impeding ROS penetration. The acquired resistance to ROS can be significantly reduced by incorporating additional Fe(3+) into the culture medium or disrupting the H(2)S biosynthetic gene. These observations suggest that careful consideration is required when utilizing ROS against Gram-negative bacteria. It is anticipated that understanding this resistance mechanism can inform the development of future antimicrobial agents, particularly for Gram-negative bacteria. | 2025 | 40948366 |
| 8524 | 8 | 0.9978 | Tebuconazole 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. | 2024 | 39277355 |
| 8982 | 9 | 0.9977 | Ampicillin 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. | 2025 | 40346915 |
| 8540 | 10 | 0.9977 | Metagenomic insights into the mechanism for the rapid enrichment and high stability of Candidatus Brocadia facilitated by Fe(Ⅲ). The rapid enrichment of anammox bacteria and its fragile resistance to adverse environment are the critical problems facing of anammox processes. As an abundant component in anammox bacteria, iron has been proved to promote the activity and growth of anammox bacteria in the mature anammox systems, but the functional and metabolic profiles in Fe(III) enhanced emerging anammox systems have not been evaluated. Results indicated that the relative abundance of functional genes involved in oxidative phosphorylation, nitrogen metabolism, cofactors synthesis, and extracellular polymers synthesis pathways was significantly promoted in the system added with 5 mg/L Fe(III) (R5). These enhanced pathways were crucial to energy generation, nitrogen removal, cell activity and proliferation, and microbial self-defense, thereby accelerating the enrichment of anammox bacteria Ca. Brocadia and facilitating their resistance to adverse environments. Microbial community analysis showed that the proportion of Ca. Brocadia in R5 also increased to 64.42 %. Hence, R5 could adapt rapidly to the increased nitrogen loading rate and increase the nitrogen removal rate by 108 % compared to the system without Fe(III) addition. However, the addition of 10 and 20 mg/L Fe(III) showed inhibitory effects on the growth and activity of anammox bacteria, which exhibited the lower relative abundance of Ca. Brocadia and unstable or even collapsed nitrogen removal performance. This study not only clarified the concentration range of Fe(III) that promoted and inhibited the enrichment of anammox bacteria, but also deepened our understanding of the functional and metabolic mechanisms underlying enhanced enrichment of anammox bacteria by Fe(III), providing a potential strategy to hasten the start-up of anammox from conventional activated sludge. | 2024 | 38309072 |
| 8819 | 11 | 0.9977 | Responses 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. | 2023 | 37195605 |
| 8333 | 12 | 0.9977 | Role of Extracellular DNA in Bacterial Response to SOS-Inducing Drugs. The SOS response is a conserved stress response pathway that is triggered by DNA damage in the bacterial cell. Activation of this pathway can, in turn, cause the rapid appearance of new mutations, sometimes called hypermutation. We compared the ability of various SOS-inducing drugs to trigger the expression of RecA, cause hypermutation, and produce elongation of bacteria. During this study, we discovered that these SOS phenotypes were accompanied by the release of large amounts of DNA into the extracellular medium. The release of DNA was accompanied by a form of bacterial aggregation in which the bacteria became tightly enmeshed in DNA. We hypothesize that DNA release triggered by SOS-inducing drugs could promote the horizontal transfer of antibiotic resistance genes by transformation or by conjugation. | 2023 | 37107011 |
| 8601 | 13 | 0.9977 | Herbicide promotes the conjugative transfer of multi-resistance genes by facilitating cellular contact and plasmid transfer. The global dissemination of antibiotic resistance genes (ARGs), especially via plasmid-mediated horizontal transfer, is becoming a pervasive health threat. While our previous study found that herbicides can accelerate the horizontal gene transfer (HGT) of ARGs in soil bacteria, the underlying mechanisms by which herbicides promote the HGT of ARGs across and within bacterial genera are still unclear. Here, the underlying mechanism associated with herbicide-promoted HGT was analyzed by detecting intracellular reactive oxygen species (ROS) production, extracellular polymeric substance composition, cell membrane integrity and proton motive force combined with genome-wide RNA sequencing. Exposure to herbicides induced a series of the above bacterial responses to promote HGT except for the ROS response, including compact cell-to-cell contact by enhancing pilus-encoded gene expression and decreasing cell surface charge, increasing cell membrane permeability, and enhancing the proton motive force, providing additional power for DNA uptake. This study provides a mechanistic understanding of the risk of bacterial resistance spread promoted by herbicides, which elucidates a new perspective on nonantibiotic agrochemical acceleration of the HGT of ARGs. | 2022 | 34969463 |
| 714 | 14 | 0.9977 | Cell wall stress responses in Bacillus subtilis: the regulatory network of the bacitracin stimulon. In response to sublethal concentrations of antibiotics, bacteria often induce an adaptive response that can contribute to antibiotic resistance. We report the response of Bacillus subtilis to bacitracin, an inhibitor of cell wall biosynthesis found in its natural environment. Analysis of the global transcriptional profile of bacitracin-treated cells reveals a response orchestrated by two alternative sigma factors (sigmaB and sigmaM) and three two-component systems (YvqEC, YvcPQ and BceRS). All three two-component systems are located next to target genes that are strongly induced by bacitracin, and the corresponding histidine kinases share an unusual topology: they lack about 100 amino acids in their extracellular sensing domain, which is almost entirely buried in the cytoplasmic membrane. Sequence analysis indicates that this novel N-terminal sensing domain is a characteristic feature of a subfamily of histidine kinases, found almost entirely in Gram-positive bacteria and frequently linked to ABC transporters. A systematic mutational analysis of bacitracin-induced genes led to the identification of a new bacitracin-resistance determinant, bceAB, encoding a putative ABC transporter. The bcrC bacitracin resistance gene, which is under the dual control of sigmaX and sigmaM, was also induced by bacitracin. By comparing the bacitracin and the vancomycin stimulons, we can differentiate between loci induced specifically by bacitracin and those that are induced by multiple cell wall-active antibiotics. | 2003 | 14651641 |
| 8608 | 15 | 0.9977 | Bisphenols can promote antibiotic resistance by inducing metabolic adaptations and natural transformation. Whether bisphenols, as plasticizers, can influence bacterial uptake of antibiotic resistance genes (ARGs) in natural environment, as well as the underlying mechanism remains largely unknown. Our results showed that four commonly used bisphenols (bisphenol A, S, F, and AF) at their environmental relative concentrations can significantly promote transmission of ARGs by 2.97-3.56 times in Acinetobacter baylyi ADP1. Intriguingly, we observed ADP1 acquired resistance by integrating plasmids uptake and cellular metabolic adaptations other than through reactive oxygen species mediated pathway. Metabolic adaptations including upregulation of capsules polysaccharide biosynthesis and intracellularly metabolic enzymes, which enabled formation of thicker capsules for capturing free plasmids, and degradation of accumulated compounds. Simultaneously, genes encoding DNA uptake and translocation machinery were incorporated to enhance natural transformation of antibiotic resistance carrying plasmids. We further exposed aquatic fish to bisphenols for 120 days to monitor their long-term effects in aquatic environment, which showed that intestinal bacteria communities were dominated by a drug resistant microbiome. Our study provides new insight into the mechanism of enhanced natural transformation of ARGs by bisphenols, and highlights the investigations for unexpectedly-elevated antibiotic-resistant risks by structurally related environmental chemicals. | 2024 | 38554512 |
| 8191 | 16 | 0.9977 | When the going gets tough, the tough get going-Novel bacterial AAA+ disaggregases provide extreme heat resistance. Heat stress can lead to protein misfolding and aggregation, potentially causing cell death due to the loss of essential proteins. Bacteria, being particularly exposed to environmental stress, are equipped with disaggregases that rescue these aggregated proteins. The bacterial Hsp70 chaperone DnaK and the ATPase associated with diverse cellular activities protein ClpB form the canonical disaggregase in bacteria. While this combination operates effectively during physiological heat stress, it is ineffective against massive aggregation caused by temperature-based sterilization protocols used in the food industry and clinics. This leaves bacteria unprotected against these thermal processes. However, bacteria that can withstand extreme, man-made stress conditions have emerged. These bacteria possess novel ATPase associated with diverse cellular activities disaggregases, ClpG and ClpL, which are key players in extreme heat resistance. These disaggregases, present in selected Gram-negative or Gram-positive bacteria, respectively, function superiorly by exhibiting increased thermal stability and enhanced threading power compared to DnaK/ClpB. This enables ClpG and ClpL to operate at extreme temperatures and process large and tight protein aggregates, thereby contributing to heat resistance. The genes for ClpG and ClpL are often encoded on mobile genomic islands or conjugative plasmids, allowing for their rapid spread among bacteria via horizontal gene transfer. This threatens the efficiency of sterilization protocols. In this review, we describe the various bacterial disaggregases identified to date, characterizing their commonalities and the specific features that enable these novel disaggregases to provide stress protection against extreme stress conditions. | 2024 | 39039821 |
| 763 | 17 | 0.9976 | Inducing conformational preference of the membrane protein transporter EmrE through conservative mutations. Transporters from bacteria to humans contain inverted repeat domains thought to arise evolutionarily from the fusion of smaller membrane protein genes. Association between these domains forms the functional unit that enables transporters to adopt distinct conformations necessary for function. The small multidrug resistance (SMR) family provides an ideal system to explore the role of mutations in altering conformational preference since transporters from this family consist of antiparallel dimers that resemble the inverted repeats present in larger transporters. Here, we show using NMR spectroscopy how a single conservative mutation introduced into an SMR dimer is sufficient to change the resting conformation and function in bacteria. These results underscore the dynamic energy landscape for transporters and demonstrate how conservative mutations can influence structure and function. | 2019 | 31637997 |
| 8526 | 18 | 0.9976 | Size-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. | 2022 | 35278945 |
| 8340 | 19 | 0.9976 | Iron-Induced Respiration Promotes Antibiotic Resistance in Actinomycete Bacteria. The bacterial response to antibiotics eliciting resistance is one of the key challenges in global health. Despite many attempts to understand intrinsic antibiotic resistance, many of the underlying mechanisms still remain elusive. In this study, we found that iron supplementation promoted antibiotic resistance in Streptomyces coelicolor. Iron-promoted resistance occurred specifically against bactericidal antibiotics, irrespective of the primary target of antibiotics. Transcriptome profiling revealed that some genes in the central metabolism and respiration were upregulated under iron-replete conditions. Iron supported the growth of S. coelicolor even under anaerobic conditions. In the presence of potassium cyanide, which reduces aerobic respiration of cells, iron still promoted respiration and antibiotic resistance. This suggests the involvement of a KCN-insensitive type of respiration in the iron effect. This phenomenon was also observed in another actinobacterium, Mycobacterium smegmatis. Taken together, these findings provide insight into a bacterial resistance strategy that mitigates the activity of bactericidal antibiotics whose efficacy accompanies oxidative damage by switching the respiration mode. IMPORTANCE A widely investigated mode of antibiotic resistance occurs via mutations and/or by horizontal acquisition of resistance genes. In addition to this acquired resistance, most bacteria exhibit intrinsic resistance as an inducible and adaptive response to different classes of antibiotics. Increasing attention has been paid recently to intrinsic resistance mechanisms because this may provide novel therapeutic targets that help rejuvenate the efficacy of the current antibiotic regimen. In this study, we demonstrate that iron promotes the intrinsic resistance of aerobic actinomycetes Streptomyces coelicolor and Mycobacterium smegmatis against bactericidal antibiotics. A surprising role of iron to increase respiration, especially in a mode of using less oxygen, appears a fitting strategy to cope with bactericidal antibiotics known to kill bacteria through oxidative damage. This provides new insights into developing antimicrobial treatments based on the availability of iron and oxygen. | 2022 | 35357210 |