scholarly journals Death by Cystine: an Adverse Emergent Property from a Beneficial Series of Reactions

2015 ◽  
Vol 197 (23) ◽  
pp. 3626-3628 ◽  
Author(s):  
Larry Reitzer
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Sulfur Metabolism ◽  
Emergent Property ◽  
Futile Cycle ◽  
Content Type ◽  
Link Type

In this issue of theJournal of Bacteriology, Chonoles Imlay et al. (K. R. Chonoles Imlay, S. Korshunov, and J. A. Imlay, J Bacteriol 197:3629–3644, 2015,http://dx.doi.org/10.1128/JB.00277-15) show that oxidative stress kills sulfur-restrictedEscherichia coligrown with sublethal H2O2when challenged with cystine. Killing requires rapid and seemingly unregulated cystine transport and equally rapid cystine reduction to cysteine. Cysteine export completes an energy-depleting futile cycle. Each reaction of the cycle could be beneficial. Together, a cystine-mediated vulnerability emerges during the transition from a sulfur-restricted to a sulfur-replete environment, perhaps because of complexities of sulfur metabolism.

scholarly journals Pathovar Transcriptomes

mSystems ◽  
2017 ◽  
Vol 2 (4) ◽  
Author(s):  
Amy Platenkamp ◽  
Jay L. Mellies
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Regulatory Networks ◽  
Virulence Gene ◽  
Model System ◽  
Genomic Sequences ◽  
Bacterial Strains ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Link Type

ABSTRACT Archetypal pathogenic bacterial strains are often used to elucidate regulatory networks of an entire pathovar, which encompasses multiple lineages and phylogroups. With enteropathogenic Escherichia coli (EPEC) as a model system, Hazen and colleagues (mSystems 6:e00024-17, 2017, https://doi.org/10.1128/mSystems.00024-17 ) used 9 isolates representing 8 lineages and 3 phylogroups to find that isolates with similar genomic sequences exhibit similarities in global transcriptomes under conditions of growth in medium that induces virulence gene expression, and they found variation among individual isolates. Archetypal pathogenic bacterial strains are often used to elucidate regulatory networks of an entire pathovar, which encompasses multiple lineages and phylogroups. With enteropathogenic Escherichia coli (EPEC) as a model system, Hazen and colleagues (mSystems 6:e00024-17, 2017, https://doi.org/10.1128/mSystems.00024-17 ) used 9 isolates representing 8 lineages and 3 phylogroups to find that isolates with similar genomic sequences exhibit similarities in global transcriptomes under conditions of growth in medium that induces virulence gene expression. They also found variation among individual isolates. Their work illustrates the importance of moving beyond observing regulatory phenomena of a limited number of regulons in a few archetypal strains, with the possibility of correlating clinical symptoms to key transcriptional pathways across lineages and phylogroups.

PBP4 and PBP5 are involved in regulating exopolysaccharide synthesis during Escherichia coli biofilm formation

Microbiology ◽  
2021 ◽  
Vol 167 (3) ◽  
Author(s):  
Sathi Mallick ◽  
Shanti Kiran ◽  
Tapas Kumar Maiti ◽  
Anindya S. Ghosh
Keyword(s):  
Escherichia Coli ◽  
Biofilm Formation ◽  
Type Species ◽  
Pentose Phosphate ◽  
Bacterial Cells ◽  
Surface Adhesion ◽  
Content Type ◽  
Penicillin Binding Proteins ◽  
E Coli ◽  
Link Type

Escherichia coli low-molecular-mass (LMM) Penicillin-binding proteins (PBPs) help in hydrolysing the peptidoglycan fragments from their cell wall and recycling them back into the growing peptidoglycan matrix, in addition to their reported involvement in biofilm formation. Biofilms are external slime layers of extra-polymeric substances that sessile bacterial cells secrete to form a habitable niche for themselves. Here, we hypothesize the involvement of Escherichia coli LMM PBPs in regulating the nature of exopolysaccharides (EPS) prevailing in its extra-polymeric substances during biofilm formation. Therefore, this study includes the assessment of physiological characteristics of E. coli CS109 LMM PBP deletion mutants to address biofilm formation abilities, viability and surface adhesion. Finally, EPS from parent CS109 and its ΔPBP4 and ΔPBP5 mutants were purified and analysed for sugars present. Deletions of LMM PBP reduced biofilm formation, bacterial adhesion and their viability in biofilms. Deletions also diminished EPS production by ΔPBP4 and ΔPBP5 mutants, purification of which suggested an increased overall negative charge compared with their parent. Also, EPS analyses from both mutants revealed the appearance of an unusual sugar, xylose, that was absent in CS109. Accordingly, the reason for reduced biofilm formation in LMM PBP mutants may be speculated as the subsequent production of xylitol and a hindrance in the standard flow of the pentose phosphate pathway.

scholarly journals d-Serine induces distinct transcriptomes in diverse Escherichia coli pathotypes

Microbiology ◽  
2021 ◽  
Vol 167 (10) ◽  
Author(s):  
James P. R. Connolly ◽  
Natasha C. A. Turner ◽  
Jennifer C. Hallam ◽  
Patricia T. Rimbi ◽  
Tom Flett ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Type Species ◽  
Pathogenic Bacteria ◽  
Neonatal Meningitis ◽  
Published Data ◽  
Toxic Metabolite ◽  
Transcriptional Responses ◽  
Content Type ◽  
E Coli ◽  
Link Type

Appropriate interpretation of environmental signals facilitates niche specificity in pathogenic bacteria. However, the responses of niche-specific pathogens to common host signals are poorly understood. d-Serine (d-ser) is a toxic metabolite present in highly variable concentrations at different colonization sites within the human host that we previously found is capable of inducing changes in gene expression. In this study, we made the striking observation that the global transcriptional response of three Escherichia coli pathotypes – enterohaemorrhagic E. coli (EHEC), uropathogenic E. coli (UPEC) and neonatal meningitis-associated E. coli (NMEC) – to d-ser was highly distinct. In fact, we identified no single differentially expressed gene common to all three strains. We observed the induction of ribosome-associated genes in extraintestinal pathogens UPEC and NMEC only, and the induction of purine metabolism genes in gut-restricted EHEC, and UPEC indicating distinct transcriptional responses to a common signal. UPEC and NMEC encode dsdCXA – a genetic locus required for detoxification and hence normal growth in the presence of d-ser. Specific transcriptional responses were induced in strains accumulating d-ser (WT EHEC and UPEC/NMEC mutants lacking the d-ser-responsive transcriptional activator DsdC), corroborating the notion that d-ser is an unfavourable metabolite if not metabolized. Importantly, many of the UPEC-associated transcriptome alterations correlate with published data on the urinary transcriptome, supporting the hypothesis that d-ser sensing forms a key part of urinary niche adaptation in this pathotype. Collectively, our results demonstrate distinct pleiotropic responses to a common metabolite in diverse E. coli pathotypes, with important implications for niche selectivity.

scholarly journals SodA Contributes to the Virulence of Avian PathogenicEscherichia coliO2 Strain E058 in Experimentally Infected Chickens

2019 ◽  
Vol 201 (6) ◽  
Author(s):  
Qingqing Gao ◽  
Le Xia ◽  
Xiaobo Wang ◽  
Zhengqin Ye ◽  
Jinbiao Liu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Hydrogen Peroxide ◽  
Virulence Factor ◽  
Infection Process ◽  
Strain Identification ◽  
Bacterial Disease ◽  
Wild Type ◽  
Content Type

ABSTRACTStrains of avian pathogenicEscherichia coli(APEC), the common pathogen of avian colibacillosis, encounter reactive oxygen species (ROS) during the infection process. Superoxide dismutases (SODs), acting as antioxidant factors, can protect against ROS-mediated host defenses. Our previous reports showed that thesodAgene (encoding a Mn-cofactor-containing SOD [MnSOD]) is highly expressed during the septicemic infection process of APEC.sodAhas been proven to be a virulence factor of certain pathogens, but its role in the pathogenicity of APEC has not been fully identified. In this study, we deleted thesodAgene from the virulent APEC O2 strain E058 and examined thein vitroandin vivophenotypes of the mutant. ThesodAmutant was more sensitive to hydrogen peroxide in terms of both its growth and viability than was the wild type. The ability to form a biofilm was weakened in thesodAmutant. ThesodAmutant was significantly more easily phagocytosed by chicken macrophages than was the wild-type strain. Chicken infection assays revealed significantly attenuated virulence of thesodAmutant compared with the wild type at 24 h postinfection. The virulence phenotype was restored by complementation of thesodAgene. Quantitative real-time reverse transcription-PCR revealed that the inactivation ofsodAreduced the expression of oxidative stress response geneskatE,perR, andosmCbut did not affect the expression ofsodBandsodC. Taken together, our studies indicate that SodA is important for oxidative resistance and virulence of APEC E058.IMPORTANCEAvian colibacillosis, caused by strains of avian pathogenicEscherichia coli, is a major bacterial disease of severe economic significance to the poultry industry worldwide. The virulence mechanisms of APEC are not completely understood. This study investigated the influence of an antioxidant protein, SodA, on the phenotype and pathogenicity of APEC O2 strain E058. This is the first report demonstrating that SodA plays an important role in protecting a specific APEC strain against hydrogen peroxide-induced oxidative stress and contributes to the virulence of this pathotype strain. Identification of this virulence factor will enhance our knowledge of APEC pathogenic mechanisms, which is crucial for designing successful strategies against associated infections and transmission.

scholarly journals Detection of an Escherichia coli Sequence Type 167 Strain with Two Tandem Copies ofblaNDM-1in the Chromosome

2016 ◽  
Vol 55 (1) ◽  
pp. 199-205 ◽  
Author(s):  
Ping Shen ◽  
Maoli Yi ◽  
Ying Fu ◽  
Zhi Ruan ◽  
Xiaoxing Du ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Insertion Sequence ◽  
Southern Blotting ◽  
Multidrug Resistant ◽  
Sequence Type ◽  
New Delhi ◽  
Genomic Context ◽  
Content Type ◽  
Link Type ◽  
Reference Genomes

ABSTRACTNew Delhi metallo-β-lactamase-1 (NDM-1)-producingEnterobacteriaceaehas disseminated rapidly throughout the world and poses an urgent threat to public health. Previous studies confirmed that theblaNDM-1gene is typically carried in plasmids but rarely in chromosome. We discovered a multidrug-resistantEscherichia colistrain Y5, originating from a urine sample and containing theblaNDM-1gene, which did not transfer by either conjugation or electrotransformation. We confirmed the possibility of its chromosome location by S1-pulsed-field gel electrophoresis (PFGE) and XbaI-PFGE, followed by Southern blotting. To determine the genomic background ofblaNDM-1, the genome of Y5 was completely sequenced and compared to other reference genomes. The results of our study revealed that this isolate consists of a 4.8-Mbp chromosome and three plasmids, it is an epidemic clone of sequence type (ST) 167, and it shows 99% identity withEscherichia coli6409 (GenBank accession no.CP010371), which lacks the sameblaNDM-1gene-surrounding structure as Y5. TheblaNDM-1gene is embedded in the chromosome along with two tandem copies of an insertion sequence common region 1 (ISCR1) element (sul1-ARR-3-cat-blaNDM-1-bleo-ISCR1), which appears intact in the plasmid fromProteus mirabilis(GenBank accession no.KP662515). The genomic context indicates that the ISCR1element mediated theblaNDM-1transposition from a single source plasmid to the chromosome. Our study is the first report of anEnterobacteriaceaestrain harboring a chromosomally integratedblaNDM-1, which directly reveals the vertical spreading pattern of the gene. Close surveillance is urgently needed to monitor the emergence and potential spread of ST167 strains that harborblaNDM-1.

scholarly journals The Catabolite Repressor Protein-Cyclic AMP Complex RegulatescsgDand Biofilm Formation in Uropathogenic Escherichia coli

2016 ◽  
Vol 198 (24) ◽  
pp. 3329-3334 ◽  
Author(s):  
David A. Hufnagel ◽  
Margery L. Evans ◽  
Sarah E. Greene ◽  
Jerome S. Pinkner ◽  
Scott J. Hultgren ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Extracellular Matrix ◽  
Cyclic Amp ◽  
Intergenic Region ◽  
Biofilm Formation ◽  
Cellulose Production ◽  
Content Type ◽  
E Coli ◽  
Link Type ◽  
K1 Capsule

ABSTRACTThe extracellular matrix protectsEscherichia colifrom immune cells, oxidative stress, predation, and other environmental stresses. Production of theE. coliextracellular matrix is regulated by transcription factors that are tuned to environmental conditions. The biofilm master regulator protein CsgD upregulates curli and cellulose, the two major polymers in the extracellular matrix of uropathogenicE. coli(UPEC) biofilms. We found that cyclic AMP (cAMP) regulates curli, cellulose, and UPEC biofilms throughcsgD. The alarmone cAMP is produced by adenylate cyclase (CyaA), and deletion ofcyaAresulted in reduced extracellular matrix production and biofilm formation. Thecataboliterepressorprotein (CRP) positively regulatedcsgDtranscription, leading to curli and cellulose production in the UPEC isolate, UTI89. Glucose, a known inhibitor of CyaA activity, blocked extracellular matrix formation when added to the growth medium. The mutant strains ΔcyaAand Δcrpdid not produce rugose biofilms, pellicles, curli, cellulose, or CsgD. Three putative CRP binding sites were identified within thecsgD-csgBintergenic region, and purified CRP could gel shift thecsgD-csgBintergenic region. Additionally, we found that CRP binded upstream ofkpsMT, which encodes machinery for K1 capsule production. Together our work shows that cAMP and CRP influenceE. colibiofilms through transcriptional regulation ofcsgD.IMPORTANCEThecataboliterepressorprotein (CRP)-cyclic AMP (cAMP) complex influences the transcription of ∼7% of genes on theEscherichia colichromosome (D. Zheng, C. Constantinidou, J. L. Hobman, and S. D. Minchin, Nucleic Acids Res 32:5874–5893, 2004,https://dx.doi.org/10.1093/nar/gkh908). Glucose inhibitsE. colibiofilm formation, and ΔcyaAand Δcrpmutants show impaired biofilm formation (D. W. Jackson, J.W. Simecka, and T. Romeo, J Bacteriol 184:3406–3410, 2002,https://dx.doi.org/10.1128/JB.184.12.3406-3410.2002). We determined that the cAMP-CRP complex regulates curli and cellulose production and the formation of rugose and pellicle biofilms throughcsgD. Additionally, we propose that cAMP may work as a signaling compound for uropathogenicE. coli(UPEC) to transition from the bladder lumen to inside epithelial cells for intracellular bacterial community formation through K1 capsule regulation.

scholarly journals Proline Metabolism IncreaseskatGExpression and Oxidative Stress Resistance in Escherichia coli

2014 ◽  
Vol 197 (3) ◽  
pp. 431-440 ◽  
Author(s):  
Lu Zhang ◽  
James R. Alfano ◽  
Donald F. Becker
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Hydrogen Peroxide ◽  
Mutant Strain ◽  
Stress Resistance ◽  
Proline Metabolism ◽  
Wild Type ◽  
Content Type ◽  
Oxidative Stress Resistance ◽  
Proline Utilization

The oxidation ofl-proline to glutamate in Gram-negative bacteria is catalyzed by the proline utilization A (PutA) flavoenzyme, which contains proline dehydrogenase (PRODH) and Δ1-pyrroline-5-carboxylate (P5C) dehydrogenase domains in a single polypeptide. Previous studies have suggested that aside from providing energy, proline metabolism influences oxidative stress resistance in different organisms. To explore this potential role and the mechanism, we characterized the oxidative stress resistance of wild-type andputAmutant strains ofEscherichia coli. Initial stress assays revealed that theputAmutant strain was significantly more sensitive to oxidative stress than the parental wild-type strain. Expression of PutA in theputAmutant strain restored oxidative stress resistance, confirming that depletion of PutA was responsible for the oxidative stress phenotype. Treatment of wild-type cells with proline significantly increased hydroperoxidase I (encoded bykatG) expression and activity. Furthermore, the ΔkatGstrain failed to respond to proline, indicating a critical role for hydroperoxidase I in the mechanism of proline protection. The global regulator OxyR activates the expression ofkatGalong with several other genes involved in oxidative stress defense. In addition tokatG, proline increased the expression ofgrxA(glutaredoxin 1) andtrxC(thioredoxin 2) of the OxyR regulon, implicating OxyR in proline protection. Proline oxidative metabolism was shown to generate hydrogen peroxide, indicating that proline increases oxidative stress tolerance inE. colivia a preadaptive effect involving endogenous hydrogen peroxide production and enhanced catalase-peroxidase activity.

scholarly journals Tail-Anchored Inner Membrane Protein ElaB Increases Resistance to Stress While Reducing Persistence in Escherichia coli

2017 ◽  
Vol 199 (9) ◽  
Author(s):  
Yunxue Guo ◽  
Xiaoxiao Liu ◽  
Baiyuan Li ◽  
Jianyun Yao ◽  
Thomas K. Wood ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Membrane Proteins ◽  
Membrane Protein ◽  
Stationary Phase ◽  
Transmembrane Domain ◽  
Inner Membrane ◽  
Content Type ◽  
E Coli ◽  
Inner Membrane Protein

ABSTRACT Host-associated bacteria, such as Escherichia coli, often encounter various host-related stresses, such as nutritional deprivation, oxidative stress, and temperature shifts. There is growing interest in searching for small endogenous proteins that mediate stress responses. Here, we characterized the small C-tail-anchored inner membrane protein ElaB in E. coli. ElaB belongs to a class of tail-anchored inner membrane proteins with a C-terminal transmembrane domain but lacking an N-terminal signal sequence for membrane targeting. Proteins from this family have been shown to play vital roles, such as in membrane trafficking and apoptosis, in eukaryotes; however, their role in prokaryotes is largely unexplored. Here, we found that the transcription of elaB is induced in the stationary phase in E. coli and stationary-phase sigma factor RpoS regulates elaB transcription by binding to the promoter of elaB. Moreover, ElaB protects cells against oxidative stress and heat shock stress. However, unlike membrane peptide toxins TisB and GhoT, ElaB does not lead to cell death, and the deletion of elaB greatly increases persister cell formation. Therefore, we demonstrate that disruption of C-tail-anchored inner membrane proteins can reduce stress resistance; it can also lead to deleterious effects, such as increased persistence, in E. coli. IMPORTANCE Escherichia coli synthesizes dozens of poorly understood small membrane proteins containing a predicted transmembrane domain. In this study, we characterized the function of the C-tail-anchored inner membrane protein ElaB in E. coli. ElaB increases resistance to oxidative stress and heat stress, while inactivation of ElaB leads to high persister cell formation. We also demonstrated that the transcription of elaB is under the direct regulation of stationary-phase sigma factor RpoS. Thus, our study reveals that small inner membrane proteins may have important cellular roles during the stress response.

scholarly journals Sigma S-Dependent Antioxidant Defense Protects Stationary-Phase Escherichia coli against the Bactericidal Antibiotic Gentamicin

2014 ◽  
Vol 58 (10) ◽  
pp. 5964-5975 ◽  
Author(s):  
Jing-Hung Wang ◽  
Rachna Singh ◽  
Michael Benoit ◽  
Mimi Keyhan ◽  
Matthew Sylvester ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Stationary Phase ◽  
Antioxidant Defense ◽  
Physiological State ◽  
Pentose Phosphate ◽  
Phase Cell ◽  
Content Type

ABSTRACTStationary-phase bacteria are important in disease. The σs-regulated general stress response helps them become resistant to disinfectants, but the role of σsin bacterial antibiotic resistance has not been elucidated. Loss of σsrendered stationary-phaseEscherichia colimore sensitive to the bactericidal antibiotic gentamicin (Gm), and proteomic analysis suggested involvement of a weakened antioxidant defense. Use of the psfiAgenetic reporter, 3′-(p-hydroxyphenyl) fluorescein (HPF) dye, and Amplex Red showed that Gm generated more reactive oxygen species (ROS) in the mutant. HPF measurements can be distorted by cell elongation, but Gm did not affect stationary-phase cell dimensions. Coadministration of the antioxidantN-acetyl cysteine (NAC) decreased drug lethality particularly in the mutant, as did Gm treatment under anaerobic conditions that prevent ROS formation. Greater oxidative stress, due to insufficient quenching of endogenous ROS and/or respiration-linked electron leakage, therefore contributed to the greater sensitivity of the mutant; infection by a uropathogenic strain in mice showed this to be the case alsoin vivo. Disruption of antioxidant defense by eliminating the quencher proteins, SodA/SodB and KatE/SodA, or the pentose phosphate pathway proteins, Zwf/Gnd and TalA, which provide NADPH for ROS decomposition, also generated greater oxidative stress and killing by Gm. Thus, besides its established mode of action, Gm also kills stationary-phase bacteria by generating oxidative stress, and targeting the antioxidant defense ofE. colican enhance its efficacy. Relevant aspects of the current controversy on the role of ROS in killing by bactericidal drugs of exponential-phase bacteria, which represent a different physiological state, are discussed.

scholarly journals Overexpression offetA(ybbL) andfetB(ybbM), Encoding an Iron Exporter, Enhances Resistance to Oxidative Stress in Escherichia coli

2013 ◽  
Vol 79 (23) ◽  
pp. 7210-7219 ◽  
Author(s):  
Sergios A. Nicolaou ◽  
Alan G. Fast ◽  
Eiko Nakamaru-Ogiso ◽  
Eleftherios T. Papoutsakis
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Iron Overload ◽  
Parent Strain ◽  
Iron Homeostasis ◽  
Intracellular Iron ◽  
Paramagnetic Resonance ◽  
Content Type ◽  
Genomic Libraries ◽  
Metal Transporter

ABSTRACTReactive oxygen species are generated by redox reactions and the Fenton reaction of H2O2and iron that generates the hydroxyl radical that causes severe DNA, protein, and lipid damage. We screenedEscherichia coligenomic libraries to identify a fragment, containingcueR,ybbJ,qmcA,ybbL, andybbM, which enhanced resistance to H2O2stress. We report that the ΔybbLand ΔybbMstrains are more susceptible to H2O2stress than the parent strain and thatybbLandybbMoverexpression overcomes H2O2sensitivity. TheybbLandybbMgenes are predicted to code for an ATP-binding cassette metal transporter, and we demonstrate that YbbM is a membrane protein. We investigated various metals to identify iron as the likely substrate of this transporter. We propose the gene namesfetAandfetB(for Fe transport) and the gene product names FetA and FetB. FetAB allows for increased resistance to oxidative stress in the presence of iron, revealing a role in iron homeostasis. We show that iron overload coupled with H2O2stress is abrogated byfetAandfetBoverexpression in the parent strain and in the Δfurstrain, where iron uptake is deregulated. Furthermore, we utilized whole-cell electron paramagnetic resonance to show that intracellular iron levels in the Δfurstrain are decreased by 37% byfetAandfetBoverexpression. Combined, these findings show thatfetAandfetBencode an iron exporter that has a role in enhancing resistance to H2O2-mediated oxidative stress and can minimize oxidative stress under conditions of iron overload and suggest that FetAB facilitates iron homeostasis to decrease oxidative stress.

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