# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 6231 | 0 | 1.0000 | NMR structure and calcium-binding properties of the tellurite resistance protein TerD from Klebsiella pneumoniae. The tellurium oxyanion TeO(3)(2-) has been used in the treatment of infectious diseases caused by mycobacteria. However, many pathogenic bacteria show tellurite resistance. Several tellurite resistance genes have been identified, and these genes mediate responses to diverse extracellular stimuli, but the mechanisms underlying their functions are unknown. To shed light on the function of KP-TerD, a 20.5 -kDa tellurite resistance protein from a plasmid of Klebsiella pneumoniae, we have determined its three-dimensional structure in solution using NMR spectroscopy. KP-TerD contains a β-sandwich formed by two five-stranded β-sheets and six short helices. The structure exhibits two negative clusters in loop regions on the top of the sandwich, suggesting that KP-TerD may bind metal ions. Indeed, thermal denaturation experiments monitored by circular dichroism and NMR studies reveal that KP-TerD binds Ca(2+). Inductively coupled plasma-optical emission spectroscopy shows that the binding ratio of KP-TerD to Ca(2+) is 1:2. EDTA (ethylenediaminetetraacetic acid) titrations of Ca(2+)-saturated KP-TerD monitored by one-dimensional NMR yield estimated dissociation constants of 18 and 200 nM for the two Ca(2+)-binding sites of KP-TerD. NMR structures incorporating two Ca(2+) ions define a novel bipartite Ca(2)(+)-binding motif that is predicted to be highly conserved in TerD proteins. Moreover, these Ca(2+)-binding sites are also predicted to be present in two additional tellurite resistance proteins, TerE and TerZ. These results suggest that some form of Ca(2+) signaling plays a crucial role in tellurite resistance and in other responses of bacteria to multiple external stimuli that depend on the Ter genes. | 2011 | 21112337 |
| 8381 | 1 | 0.9994 | The Klebsiella pneumoniae tellurium resistance gene terC contributes to both tellurite and zinc resistance. Klebsiella pneumoniae is widely recognized as a pathogen responsible for hospital-acquired infections and community-acquired invasive infections. It has rapidly become a significant global public health threat due to the emergence of hypervirulent and multidrug-resistant strains, which have increased the challenges associated with treating life-threatening infections. Tellurium resistance genes are widespread on virulence plasmids in K. pneumoniae isolates. However, the core function of the ter operon (terZABCDEF) in K. pneumoniae remains unclear. In this study, the multidrug-resistant K. pneumoniae P1927 strain was isolated from the sputum of a hospitalized pneumonia patient. The ter operon, along with antimicrobial resistance and virulence genes, was identified on a large hybrid plasmid in K. pneumoniae P1927. We generated a terC deletion mutant and demonstrated that this mutant exhibited reduced virulence in a Galleria mellonella larva infection model. Further physiological functional analysis revealed that terC is not only important for Te(IV) resistance but also for resistance to Zn(II), Mn(II), and phage infection. All genes of the ter operon were highly inducible by Zn(II), which is a stronger inducer than Te(IV), and the terBCDE genes were also induced by Mn(II). Collectively, our study demonstrates novel physiological functions of TerC in Zn(II) resistance and virulence in K. pneumoniae.IMPORTANCEKlebsiella pneumoniae has rapidly become a global threat to public health. Although the ter operon is widely identified in clinical isolates, its physiological function remains unclear. It has been proposed that proteins encoded by the ter operon form a multi-site metal-binding complex, but its exact function is still unknown. TerC, a central component of the tellurium resistance determinant, was previously shown to interact with outer membrane proteins OmpA and KpsD in Escherichia coli, suggesting potential changes in outer membrane structure and properties. Here, we report that TerC confers resistance to Zn(II), Mn(II), and phage infection, and Zn(II) was shown to be a strong inducer of the ter operon. Furthermore, TerC was identified as a novel virulence factor. Taken together, our results expand our understanding of the physiological functions encoded by the ter operon and its role in the virulence of K. pneumoniae, providing deeper insights into the link between heavy metal(loid) resistance determinants and virulence in pathogenic bacteria. | 2025 | 40202338 |
| 8907 | 2 | 0.9993 | 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 |
| 6318 | 3 | 0.9993 | Phenotypic differences between Salmonella and Escherichia coli resulting from the disparate regulation of homologous genes. Phenotypic differences among closely related bacteria have been largely ascribed to species-specific genes, such as those residing in pathogenicity islands. However, we now report that the differential regulation of homologous genes is the mechanism responsible for the divergence of the enteric bacteria Salmonella enterica and Escherichia coli in their ability to make LPS modifications mediating resistance to the antibiotic polymyxin B. In S. enterica serovar Typhimurium, the PmrA/PmrB two-component system governing polymyxin B resistance is induced in low Mg(2+) in a process that requires the PmrD protein and by Fe(3+) in a PmrD-independent fashion. We establish that E. coli K-12 induces PmrA-activated gene transcription and polymyxin B resistance in response to Fe(3+), but that it is blind to the low Mg(2+) signal. The highly divergent PmrD protein is responsible for this phenotype as replacement of the E. coli pmrD gene by its Salmonella counterpart resulted in an E. coli strain that transcribed PmrA-activated genes and displayed polymyxin B resistance under the same conditions as Salmonella. Molecular analysis of natural isolates of E. coli and Salmonella revealed that the PmrD proteins are conserved within each genus and that selection might have driven the divergence between the Salmonella and E. coli PmrD proteins. Investigation of PmrD function demonstrated statistically different distributions for the Salmonella and E. coli isolates in PmrD-dependent transcription occurring in low Mg(2+). Our results suggest that the differential regulation of conserved genes may have ecological consequences, determining the range of niches a microorganism can occupy. | 2004 | 15569938 |
| 4707 | 4 | 0.9993 | Comparative transcriptome analyses of magainin I-susceptible and -resistant Escherichia coli strains. Antimicrobial peptides (AMPs) have attracted considerable attention because of their multiple and complex mechanisms of action toward resistant bacteria. However, reports have increasingly highlighted how bacteria can escape AMP administration. Here, the molecular mechanisms involved in Escherichia coli resistance to magainin I were investigated through comparative transcriptomics. Sub-inhibitory concentrations of magainin I were used to generate four experimental groups, including magainin I-susceptible E. coli, in the absence (C) and presence of magainin I (CM); and magainin I-resistant E. coli in the absence (R) and presence of magainin I (RM). The total RNA from each sample was extracted; cDNA libraries were constructed and further submitted for Illumina MiSeq sequencing. After RNA-seq data pre-processing and functional annotation, a total of 103 differentially expressed genes (DEGs) were identified, mainly related to bacterial metabolism. Moreover, down-regulation of cell motility and chaperone-related genes was observed in CM and RM, whereas cell communication, acid tolerance and multidrug efflux pump genes (ABC transporter, major facilitator and resistance-nodulation cell division superfamilies) were up-regulated in these same groups. DEGs from the C and R groups are related to basal levels of expression of homeostasis-related genes compared to CM and RM, suggesting that the presence of magainin I is required to change the transcriptomics panel in both C and R E. coli strains. These findings show the complexity of E. coli resistance to magainin I through the rearrangement of several metabolic pathways involved in bacterial physiology and drug response, also providing information on the development of novel antimicrobial strategies targeting resistance-related transcripts and proteins herein described. | 2018 | 30277857 |
| 4708 | 5 | 0.9993 | Proteomic analysis of nalidixic acid resistance in Escherichia coli: identification and functional characterization of OM proteins. The worldwide emergence of antibiotic-resistant bacteria poses a serious threat to human health. To understand the mechanisms of the resistance is extremely important to the control of these bacteria. In the current study, proteomic methodologies were utilized to characterize OM proteome of Escherichia coli with nalidixic acid (NA) resistance. The OM proteins TolC, OmpT, OmpC and OmpW were found to be up-regulated, and FadL was down-regulated in the NA-resistant E. coli strains. The changes at the level of protein expression were validated using Western blotting. Furthermore, the possible roles these altered proteins played in regulation of NA resistance were investigated using genetically modified strains with the deletion of these genes. The results obtained from functional characterization of these genetically modified strains suggest that TolC and OmpC may play more important roles in the control of NA resistance than other OM proteins identified. To gain better understanding of the mechanisms of NA resistance, we also characterized the role of the two-component system EnvZ/OmpR which is responsible for the regulation of OmpC and OmpF expression in response to NA resistance using their genetically modified strains. Our results suggest that OmpF and the EnvZ/OmpR are also important participants of the pathways regulating the NA resistance of E. coli. | 2008 | 18438992 |
| 6293 | 6 | 0.9993 | Gentamicin resistance to Escherichia coli related to fatty acid metabolism based on transcriptome analysis. Antibiotic overuse and misuse have promoted the emergence and spread of antibiotic-resistant bacteria. Increasing bacterial resistance to antibiotics is a major healthcare problem, necessitating elucidation of antibiotic resistance mechanisms. In this study, we explored the mechanism of gentamicin resistance by comparing the transcriptomes of antibiotic-sensitive and -resistant Escherichia coli. A total of 410 differentially expressed genes were identified, of which 233 (56.83%) were up-regulated and 177 (43.17%) were down-regulated in the resistant strain compared with the sensitive strain. Gene Ontology (GO) analysis classifies differential gene expression into three main categories: biological processes, cellular components, and molecular functions. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that the up-regulated genes were enriched in eight metabolic pathways, including fatty acid metabolism, which suggests that fatty acid metabolism may be involved in the development of gentamicin resistance in E. coli. This was demonstrated by measuring the acetyl-CoA carboxylase activity, plays a fundamental role in fatty acid metabolism, was increased in gentamicin-resistant E. coli. Treatment of fatty acid synthesis inhibitor, triclosan, promoted gentamicin-mediated killing efficacy to antibiotic-resistant bacteria. We also found that exogenous addition of oleic acid, which involved in fatty acid metabolism, reduced E. coli sensitivity to gentamicin. Overall, our results provide insight into the molecular mechanism of gentamicin resistance development in E. coli. | 2023 | 37224563 |
| 6317 | 7 | 0.9992 | O-specific polysaccharide confers lysozyme resistance to extraintestinal pathogenic Escherichia coli. Extraintestinal pathogenic Escherichia coli (ExPEC) is the leading cause of bloodstream and other extraintestinal infections in human and animals. The greatest challenge encountered by ExPEC during an infection is posed by the host defense mechanisms, including lysozyme. ExPEC have developed diverse strategies to overcome this challenge. The aim of this study was to characterize the molecular mechanism of ExPEC resistance to lysozyme. For this, 15,000 transposon mutants of a lysozyme-resistant ExPEC strain NMEC38 were screened; 20 genes were identified as involved in ExPEC resistance to lysozyme-of which five were located in the gene cluster between galF and gnd, and were further confirmed to be involved in O-specific polysaccharide biosynthesis. The O-specific polysaccharide was able to inhibit the hydrolytic activity of lysozyme; it was also required by the complete lipopolysaccharide (LPS)-mediated protection of ExPEC against the bactericidal activity of lysozyme. The O-specific polysaccharide was further shown to be able to directly interact with lysozyme. Furthermore, LPS from ExPEC strains of different O serotypes was also able to inhibit the hydrolytic activity of lysozyme. Because of their cell surface localization and wide distribution in Gram-negative bacteria, O-specific polysaccharides appear to play a long-overlooked role in protecting bacteria against exogenous lysozyme. | 2018 | 29405825 |
| 6292 | 8 | 0.9992 | Genome-Wide Screening and Characterization of Genes Involved in Response to High Dose of Ciprofloxacin in Escherichia coli. The global emergence of antibiotic resistance, especially in Gram-negative bacteria, is an urgent threat to public health. Inevitably, considering its extensive use and misuse, resistance toward ciprofloxacin has increased in almost all clinically relevant bacteria. This study aimed to investigate the transcriptome changes at a high concentration of ciprofloxacin in Escherichia coli. In brief, 1,418 differentially expressed genes (DEGs) were identified, from which 773 genes were upregulated by ciprofloxacin, whereas 651 genes were downregulated. Enriched biological pathways reflected the upregulation of biological processes such as DNA damage and repair system, toxin/antitoxin systems, formaldehyde detoxification system. With kyoto encyclopedia of genes and genomes pathway analysis, higher expressed DEGs were associated with "LPS biosynthesis," "streptomycin biosynthesis," and "polyketide sugar unit biosynthesis." Lower expressed DEGs were associated with "biosynthesis of amino acids" and "flagellar assembly" pathways. After treatment of ciprofloxacin, lipopolysaccharide (LPS) release was increased by two times, and the gene expression level of LPS synthesis was elevated (p < 0.05) in both reference and clinical strains. Our results demonstrated that transient exposure to high-dose ciprofloxacin is a double-edged sword. Cautions should be taken when administering high-dose antibiotic treatment for infectious diseases. | 2022 | 35512736 |
| 6213 | 9 | 0.9992 | Use of a Dictyostelium model for isolation of genetic loci associated with phagocytosis and virulence in Klebsiella pneumoniae. Phagocytosis resistance is an important virulence factor in Klebsiella pneumoniae. Dictyostelium has been used to study the interaction between phagocytes and bacteria because of its similarity to mammalian macrophages. In this study, we used a Dictyostelium model to investigate genes for resistance to phagocytosis in NTUH-K2044, a strain of K. pneumoniae causing pyogenic liver abscess that is highly resistant to phagocytosis. A total of 2,500 transposon mutants were screened by plaque assay, and 29 of them permitted phagocytosis by Dictyostelium. In the 29 mutants, six loci were identified; three were capsular synthesis genes. Of the other three, one was related to carnitine metabolism, one encoded a subunit of protease (clpX), and one encoded a lipopolysaccharide O-antigen transporter (wzm). Deletion and complementation of these genes showed that only ΔclpX and Δwzm mutants became susceptible to Dictyostelium phagocytosis, and their complementation restored the phagocytosis resistance phenotype. These two mutants were also susceptible to phagocytosis by human neutrophils and revealed attenuated virulence in a mouse model, implying that they play important roles in the pathogenesis of K. pneumoniae. Furthermore, we demonstrated that clpP, which exists in an operon with clpX, was also involved in resistance to phagocytosis. The transcriptional profile of ΔclpX was examined by microarray analysis and revealed a 3-fold lower level of expression of capsular synthesis genes. Therefore, we have identified genes involved in resistance to phagocytosis in K. pneumoniae using Dictyostelium, and this model is useful to explore genes associated with resistance to phagocytosis in heavily encapsulated bacteria. | 2011 | 21173313 |
| 8456 | 10 | 0.9992 | Identification of genes required by Bacillus thuringiensis for survival in soil by transposon-directed insertion site sequencing. Transposon-directed insertion site sequencing was used to identify genes required by Bacillus thuringiensis to survive in non-axenic plant/soil microcosms. A total of 516 genetic loci fulfilled the criteria as conferring survival characteristics. Of these, 127 (24.6 %) were associated with uptake and transport systems; 227 loci (44.0 %) coded for enzymatic properties; 49 (9.5 %) were gene regulation or sensory loci; 40 (7.8 %) were structural proteins found in the cell envelope or had enzymatic activities related to it and 24 (4.7 %) were involved in the production of antibiotics or resistance to them. Eighty-three (16.1 %) encoded hypothetical proteins or those of unknown function. The ability to form spores was a key survival characteristic in the microcosms: bacteria, inoculated in either spore or vegetative form, were able to multiply and colonise the soil, whereas a sporulation-deficient mutant was not. The presence of grass seedlings was critical to colonisation. Bacteria labelled with green fluorescent protein were observed to adhere to plant roots. The sporulation-specific promoter of spo0A, the key regulator of sporulation, was strongly activated in the rhizosphere. In contrast, the vegetative-specific promoters of spo0A and PlcR, a pleiotropic regulator of genes with diverse activities, were only very weakly activated. | 2014 | 24310935 |
| 6221 | 11 | 0.9992 | Characterization of the Tellurite-Resistance Properties and Identification of the Core Function Genes for Tellurite Resistance in Pseudomonas citronellolis SJTE-3. Tellurite is highly toxic to bacteria and commonly used in the clinical screening for pathogens; it is speculated that there is a potential relationship between tellurite resistance and bacterial pathogenicity. Until now, the core function genes of tellurite resistance and their characteristics are still obscure. Pseudomonas citronellolis SJTE-3 was found able to resist high concentrations of tellurite (250 μg/mL) and formed vacuole-like tellurium nanostructures. The terZABCDE gene cluster located in the large plasmid pRBL16 endowed strain SJTE-3 with the tellurite resistance of high levels. Although the terC and terD genes were identified as the core function genes for tellurite reduction and resistance, the inhibition of cell growth was observed when they were used solely. Interestingly, co-expression of the terA gene or terZ gene could relieve the burden caused by the expression of the terCD genes and recover normal cell growth. TerC and TerD proteins commonly shared the conserved sequences and are widely distributed in many pathogenic bacteria, highly associated with the pathogenicity factors. | 2022 | 35056544 |
| 6202 | 12 | 0.9992 | Zinc Blockade of SOS Response Inhibits Horizontal Transfer of Antibiotic Resistance Genes in Enteric Bacteria. The SOS response is a conserved response to DNA damage that is found in Gram-negative and Gram-positive bacteria. When DNA damage is sustained and severe, activation of error-prone DNA polymerases can induce a higher mutation rate than is normally observed, which is called the SOS mutator phenotype or hypermutation. We previously showed that zinc blocked the hypermutation response induced by quinolone antibiotics and mitomycin C in Escherichia coli and Klebsiella pneumoniae. In this study, we demonstrate that zinc blocks the SOS-induced development of chloramphenicol resistance in Enterobacter cloacae. Zinc also blocked the transfer of an extended spectrum beta-lactamase (ESBL) gene from Enterobacter to a susceptible E. coli strain. A zinc ionophore, zinc pyrithione, was ~100-fold more potent than zinc salts in inhibition of ciprofloxacin-induced hypermutation in E. cloacae. Other divalent metals, such as iron and manganese, failed to inhibit these responses. Electrophoretic mobility shift assays (EMSAs) revealed that zinc, but not iron or manganese, blocked the ability of the E. coli RecA protein to bind to single-stranded DNA, an important early step in the recognition of DNA damage in enteric bacteria. This suggests a mechanism for zinc's inhibitory effects on bacterial SOS responses, including hypermutation. | 2018 | 30519543 |
| 8965 | 13 | 0.9992 | Resistance characterization and transcriptomic analysis of imipenem-induced drug resistance in Escherichia coli. BACKGROUND: Bacteria can develop resistance to various antibiotics under selective pressure, leading to multifaceted changes in resistance mechanisms. Transcriptomic sequencing allows for the observation of transcriptional level alterations in cells under antibiotic stress. Understanding the bacterial response to such stress is essential for deciphering their strategy against drug-resistant antibiotics and identifying potential targets for antibiotic development. METHODS: This study using wild-type (WT) Escherichia coli (E. coli) discovered that continuous in vitro induction screening for imipenem-resistant strains resulted in bacteria with enhanced biofilm-forming ability and mutations in antibiotic target sites. Transcriptomic sequencing of the resistant bacteria revealed significant changes in carbon and amino acid metabolism, nutrient assimilation, substance transport, nucleotide metabolism, protein biosynthesis, and cell wall biosynthesis. The up-regulated drug efflux genes were disrupted using gene knockout technology. Drug sensitivity tests indicated that drug efflux has a minimal effect on imipenem resistance. RESULTS: This suggests a strategy for E. coli drug resistance involving the reduction of unnecessary substance synthesis and metabolism, coupled with an increase in activities that aid in resisting foreign threats. | 2024 | 39624129 |
| 8964 | 14 | 0.9992 | Analysis of the Oxidative Stress Regulon Identifies soxS as a Genetic Target for Resistance Reversal in Multidrug-Resistant Klebsiella pneumoniae. In bacteria, the defense system deployed to counter oxidative stress is orchestrated by three transcriptional factors, SoxS, SoxR, and OxyR. Although the regulon that these factors control is known in many bacteria, similar data are not available for Klebsiella pneumoniae. To address this data gap, oxidative stress was artificially induced in K. pneumoniae MGH78578 using paraquat and the corresponding oxidative stress regulon recorded using transcriptome sequencing (RNA-seq). The soxS gene was significantly induced during oxidative stress, and a knockout mutant was constructed to explore its functionality. The wild type and mutant were grown in the presence of paraquat and subjected to RNA-seq to elucidate the soxS regulon in K. pneumoniae MGH78578. Genes that are commonly regulated both in the oxidative stress and soxS regulons were identified and denoted as the oxidative SoxS regulon; these included a group of genes specifically regulated by SoxS. Efflux pump-encoding genes and global regulators were identified as part of this regulon. Consequently, the isogenic soxS mutant was found to exhibit a reduction in the minimum bactericidal concentration against tetracycline compared to that of the wild type. Impaired efflux activity, allowing tetracycline to be accumulated in the cytoplasm to bactericidal levels, was further evaluated using a tetraphenylphosphonium (TPP(+)) accumulation assay. The soxS mutant was also susceptible to tetracycline in vivo in a zebrafish embryo model. We conclude that the soxS gene could be considered a genetic target against which an inhibitor could be developed and used in combinatorial therapy to combat infections associated with multidrug-resistant K. pneumoniae. IMPORTANCE Antimicrobial resistance is a global health challenge. Few new antibiotics have been developed for use over the years, and preserving the efficacy of existing compounds is an important step to protect public health. This paper describes a study that examines the effects of exogenously induced oxidative stress on K. pneumoniae and uncovers a target that could be useful to harness as a strategy to mitigate resistance. | 2021 | 34098732 |
| 6320 | 15 | 0.9992 | Identification of the Extracytoplasmic Function σ Factor σ(P) Regulon in Bacillus thuringiensis. Bacillus thuringiensis and other members of the Bacillus cereus family are resistant to many β-lactams. Resistance is dependent upon the extracytoplasmic function sigma factor σ(P). We used label-free quantitative proteomics to identify proteins whose expression was dependent upon σ(P). We compared the protein profiles of strains which either lacked σ(P) or overexpressed σ(P). We identified 8 members of the σ(P) regulon which included four β-lactamases as well as three penicillin-binding proteins (PBPs). Using transcriptional reporters, we confirmed that these genes are induced by β-lactams in a σ(P)-dependent manner. These genes were deleted individually or in various combinations to determine their role in resistance to a subset of β-lactams, including ampicillin, methicillin, cephalexin, and cephalothin. We found that different combinations of β-lactamases and PBPs are involved in resistance to different β-lactams. Our data show that B. thuringiensis utilizes a suite of enzymes to protect itself from β-lactam antibiotics. IMPORTANCE Antimicrobial resistance is major concern for public health. β-Lactams remain an important treatment option for many diseases. However, the spread of β-lactam resistance continues to rise. Many pathogens acquire antibiotic resistance from environmental bacteria. Thus, understanding β-lactam resistance in environmental strains may provide insights into additional mechanisms of antibiotic resistance. Here, we describe how a single regulatory system, σ(P), in B. thuringiensis controls expression of multiple genes involved in resistance to β-lactams. Our findings indicate that some of these genes are partially redundant. Our data also suggest that the large number of genes controlled by σ(P) results in increased resistance to a wider range of β-lactam classes than any single gene could provide. | 2022 | 35080471 |
| 8946 | 16 | 0.9992 | Role of the CpxAR two-component signal transduction system in control of fosfomycin resistance and carbon substrate uptake. Although fosfomycin is an old antibiotic, it has resurfaced with particular interest. The antibiotic is still effective against many pathogens that are resistant to other commonly used antibiotics. We have found that fosfomycin resistance of enterohemorrhagic Escherichia coli (EHEC) O157:H7 is controlled by the bacterial two-component signal transduction system CpxAR. A cpxA mutant lacking its phosphatase activity results in constitutive activation of its cognate response regulator, CpxR, and fosfomycin resistance. We have shown that fosfomycin resistance requires CpxR because deletion of the cpxR gene in the cpxA mutant restores fosfomycin sensitivity. We have also shown that CpxR directly represses the expression of two genes, glpT and uhpT, which encode transporters that cotransport fosfomycin with their native substrates glycerol-3-phosphate and glucose-6-phosphate, and repression of these genes leads to a decrease in fosfomycin transport into the cpxA mutant. However, the cpxA mutant had an impaired growth phenotype when cultured with glycerol-3-phosphate or glucose-6-phosphate as a sole carbon substrate and was outcompeted by the parent strain, even in nutrient-rich medium. This suggests a trade-off between fosfomycin resistance and the biological fitness associated with carbon substrate uptake. We propose a role for the CpxAR system in the reversible control of fosfomycin resistance. This may be a beneficial strategy for bacteria to relieve the fitness burden that results from fosfomycin resistance in the absence of fosfomycin. | 2014 | 24163343 |
| 4824 | 17 | 0.9992 | Chemogenomic Screen for Imipenem Resistance in Gram-Negative Bacteria. Carbapenem-resistant Gram-negative bacteria are considered a major threat to global health. Imipenem (IMP) is used as a last line of treatment against these pathogens, but its efficacy is diminished by the emergence of resistance. We applied a whole-genome screen in Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa isolates that were submitted to chemical mutagenesis, selected for IMP resistance, and characterized by next-generation sequencing. A comparative analysis of IMP-resistant clones showed that most of the highly mutated genes shared by the three species encoded proteins involved in transcription or signal transduction. Of these, the rpoD gene was one of the most prevalent and an E. coli strain disrupted for rpoD displayed a 4-fold increase in resistance to IMP. E. coli and K. pneumoniae also specifically shared several mutated genes, most involved in membrane/cell envelope biogenesis, and the contribution in IMP susceptibility was experimentally proven for amidases, transferases, and transglycosidases. P. aeruginosa differed from the two Enterobacteriaceae isolates with two different resistance mechanisms, with one involving mutations in the oprD porin or, alternatively, in two-component systems. Our chemogenomic screen performed with the three species has highlighted shared and species-specific responses to IMP.IMPORTANCE Gram-negative carbapenem-resistant bacteria are a major threat to global health. The use of genome-wide screening approaches to probe for genes or mutations enabling resistance can lead to identification of molecular markers for diagnostics applications. We describe an approach called Mut-Seq that couples chemical mutagenesis and next-generation sequencing for studying resistance to imipenem in the Gram-negative bacteria Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa The use of this approach highlighted shared and species-specific responses, and the role in resistance of a number of genes involved in membrane biogenesis, transcription, and signal transduction was functionally validated. Interestingly, some of the genes identified were previously considered promising therapeutic targets. Our genome-wide screen has the potential to be extended outside drug resistance studies and expanded to other organisms. | 2019 | 31744905 |
| 9780 | 18 | 0.9992 | Colistin resistance in Escherichia coli confers protection of the cytoplasmic but not outer membrane from the polymyxin antibiotic. Colistin is a polymyxin antibiotic of last resort for the treatment of infections caused by multi-drug-resistant Gram-negative bacteria. By targeting lipopolysaccharide (LPS), the antibiotic disrupts both the outer and cytoplasmic membranes, leading to bacterial death and lysis. Colistin resistance in Escherichia coli occurs via mutations in the chromosome or the acquisition of mobilized colistin-resistance (mcr) genes. Both these colistin-resistance mechanisms result in chemical modifications to the LPS, with positively charged moieties added at the cytoplasmic membrane before the LPS is transported to the outer membrane. We have previously shown that MCR-1-mediated LPS modification protects the cytoplasmic but not the outer membrane from damage caused by colistin, enabling bacterial survival. However, it remains unclear whether this observation extends to colistin resistance conferred by other mcr genes, or resistance due to chromosomal mutations. Using a panel of clinical E. coli that had acquired mcr -1, -1.5, -2, -3, -3.2 or -5, or had acquired polymyxin resistance independently of mcr genes, we found that almost all isolates were susceptible to colistin-mediated permeabilization of the outer, but not cytoplasmic, membrane. Furthermore, we showed that permeabilization of the outer membrane of colistin-resistant isolates by the polymyxin is in turn sufficient to sensitize bacteria to the antibiotic rifampicin, which normally cannot cross the LPS monolayer. These findings demonstrate that colistin resistance in these E. coli isolates is due to protection of the cytoplasmic but not outer membrane from colistin-mediated damage, regardless of the mechanism of resistance. | 2021 | 34723787 |
| 6304 | 19 | 0.9992 | Genome-Wide Screening of Oxidizing Agent Resistance Genes in Escherichia coli. The use of oxidizing agents is one of the most favorable approaches to kill bacteria in daily life. However, bacteria have been evolving to survive in the presence of different oxidizing agents. In this study, we aimed to obtain a comprehensive list of genes whose expression can make Escherichiacoli cells resistant to different oxidizing agents. For this purpose, we utilized the ASKA library and performed a genome-wide screening of ~4200 E. coli genes. Hydrogen peroxide (H(2)O(2)) and hypochlorite (HOCl) were tested as representative oxidizing agents in this study. To further validate our screening results, we used different E. coli strains as host cells to express or inactivate selected resistance genes individually. More than 100 genes obtained in this screening were not known to associate with oxidative stress responses before. Thus, this study is expected to facilitate both basic studies on oxidative stress and the development of antibacterial agents. | 2021 | 34072091 |