scholarly journals RegR Virulence Regulon of Rabbit-Specific Enteropathogenic Escherichia coli Strain E22

2013 ◽  
Vol 81 (4) ◽  
pp. 1078-1089 ◽  
Author(s):  
Yogitha N. Srikhanta ◽  
Dianna M. Hocking ◽  
Judyta Praszkier ◽  
Matthew J. Wakefield ◽  
Roy M. Robins-Browne ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Regulatory Protein ◽  
Bioinformatic Analysis ◽  
Coli Strain ◽  
Mobility Shift ◽  
Gene Encoding ◽  
Gene Target ◽  
Content Type ◽  
E Coli ◽  
Genes Encoding

ABSTRACTAraC-like regulators play a key role in the expression of virulence factors in enteric pathogens, such as enteropathogenicEscherichia coli(EPEC), enterotoxigenicE. coli, enteroaggregativeE. coli, andCitrobacter rodentium. Bioinformatic analysis of the genome of rabbit-specific EPEC (REPEC) strain E22 (O103:H2) revealed the presence of a gene encoding an AraC-like regulatory protein, RegR, which shares 71% identity to the global virulence regulator, RegA, ofC. rodentium. Microarray analysis demonstrated that RegR exerts 25- to 400-fold activation on transcription of several genes encoding putative virulence-associated factors, including a fimbrial operon (SEF14), a serine protease, and an autotransporter adhesin. These observations were confirmed by proteomic analysis of secreted and heat-extracted surface-associated proteins. The mechanism of RegR-mediated activation was investigated by using its most highly upregulated gene target,sefA. Transcriptional analyses and electrophoretic mobility shift assays showed that RegR activates the expression ofsefAby binding to a region upstream of thesefApromoter, thereby relieving gene silencing by the global regulatory protein H-NS. Moreover, RegR was found to contribute significantly to virulence in a rabbit infection experiment. Taken together, our findings indicate that RegR controls the expression of a series of accessory adhesins that significantly enhance the virulence of REPEC strain E22.

scholarly journals Involvement of PatE, a Prophage-Encoded AraC-Like Regulator, in the Transcriptional Activation of Acid Resistance Pathways of Enterohemorrhagic Escherichia coli Strain EDL933

2012 ◽  
Vol 78 (15) ◽  
pp. 5083-5092 ◽  
Author(s):  
Jennifer K. Bender ◽  
Judyta Praszkier ◽  
Matthew J. Wakefield ◽  
Kathryn Holt ◽  
Marija Tauschek ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Transcriptional Activation ◽  
Regulatory Protein ◽  
Acid Resistance ◽  
Enterohemorrhagic Escherichia Coli ◽  
Transcriptional Analysis ◽  
Mobility Shift ◽  
Content Type ◽  
Infectious Dose ◽  
Genes Encoding

ABSTRACTEnterohemorrhagicEscherichia coli(EHEC) O157:H7 is a lethal human intestinal pathogen that causes hemorrhagic colitis and the hemolytic-uremic syndrome. EHEC is transmitted by the fecal-oral route and has a lower infectious dose than most other enteric bacterial pathogens in that fewer than 100 CFU are able to cause disease. This low infectious dose has been attributed to the ability of EHEC to survive in the acidic environment of the human stomach.In silicoanalysis of the genome of EHEC O157:H7 strain EDL933 revealed a gene,patE, for a putative AraC-like regulatory protein within the prophage island, CP-933H. Transcriptional analysis inE. colishowed that the expression ofpatEis induced during stationary phase. Data from microarray assays demonstrated that PatE activates the transcription of genes encoding proteins of acid resistance pathways. In addition, PatE downregulated the expression of a number of genes encoding heat shock proteins and the type III secretion pathway of EDL933. Transcriptional analysis and electrophoretic mobility shift assays suggested that PatE also activates the transcription of the gene for the acid stress chaperonehdeAby binding to its promoter region. Finally, assays of acid tolerance showed that increasing the expression of PatE in EHEC greatly enhanced the ability of the bacteria to survive in different acidic environments. Together, these findings indicate that EHEC strain EDL933 carries a prophage-encoded regulatory system that contributes to acid resistance.

scholarly journals Draft Genome Sequence of Escherichia coli Strain Tj, Isolated from the Varzob River in Tajikistan

2020 ◽  
Vol 9 (41) ◽  
Author(s):  
Munavvara Dzhuraeva ◽  
Mehrangez Shokirova ◽  
Ani Azaryan ◽  
Hovik Panosyan ◽  
Khursheda Bobodzhanova ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Genome Sequence ◽  
Draft Genome ◽  
Coli Strain ◽  
Draft Genome Sequence ◽  
Gene Encoding ◽  
Content Type ◽  
E Coli ◽  
Lambdoid Phage ◽  
Specific Phage

ABSTRACT The 4.6-Mbp draft genome sequence of Escherichia coli strain Tj, isolated from the Varzob River in Tajikistan, is presented. This strain possesses four prophage elements related to Shigella phage SfV, E. coli O157:H7-specific phage ϕV10, lambdoid phage HK225, and coliphage Ayreon. It contains a gene encoding a hemolysin E toxin.

scholarly journals Control of Acid Resistance Pathways of Enterohemorrhagic Escherichia coli Strain EDL933 by PsrB, a Prophage-Encoded AraC-Like Regulator

2014 ◽  
Vol 83 (1) ◽  
pp. 346-353 ◽  
Author(s):  
Ji Yang ◽  
Thomas W. Russell ◽  
Dianna M. Hocking ◽  
Jennifer K. Bender ◽  
Yogitha N. Srikhanta ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acid Resistance ◽  
Transcriptional Regulators ◽  
Coli Strain ◽  
Enterohemorrhagic Escherichia Coli ◽  
Transcriptional Analysis ◽  
Mobility Shift ◽  
Content Type ◽  
E Coli ◽  
Acidic Conditions

EnterohemorrhagicEscherichia coli(EHEC) O157:H7 causes bloody diarrhea and hemolytic-uremic syndrome (HUS) and is the most prevalentE. coliserotype associated with food-borne illness worldwide. This pathogen is transmitted via the fecal-oral route and has a low infectious dose that has been estimated to be between 10 and 100 cells. We and others have previously identified three prophage-encoded AraC-like transcriptional regulators, PatE, PsrA, and PsrB in the EHEC O157:H7 EDL933 strain. Our analysis showed that PatE plays an important role in facilitating survival of EHEC under a number of acidic conditions, but the contribution of PsrA and PsrB to acid resistance (AR) was unknown. Here, we investigated the involvement of PsrA and PsrB in the survival ofE. coliO157:H7 in acid. Our results showed that PsrB, but not PsrA, enhanced the survival of strain EDL933 under various acidic conditions. Transcriptional analysis using promoter-lacZreporters and electrophoretic mobility shift assays demonstrated that PsrB activates transcription of thehdeAoperon, which encodes a major acid stress chaperone, by interacting with its promoter region. Furthermore, using a mouse model, we showed that expression of PsrB significantly enhanced the ability of strain EDL933 to overcome the acidic barrier of the mouse stomach. Taken together, our results indicate that EDL933 acquired enhanced acid tolerance via horizontally acquired regulatory genes encoding transcriptional regulators that activate its AR machinery.

scholarly journals A Rhodobacter sphaeroides Protein Mechanistically Similar to Escherichia coli DksA Regulates Photosynthetic Growth

mBio ◽  
2014 ◽  
Vol 5 (3) ◽  
Author(s):  
Christopher W. Lennon ◽  
Kimberly C. Lemmer ◽  
Jessica L. Irons ◽  
Max I. Sellman ◽  
Timothy J. Donohue ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Structure Function ◽  
Rhodobacter Sphaeroides ◽  
Fatty Acid Content ◽  
Regulatory Protein ◽  
Growth Conditions ◽  
Globular Domain ◽  
Content Type ◽  
E Coli

ABSTRACTDksA is a global regulatory protein that, together with the alarmone ppGpp, is required for the “stringent response” to nutrient starvation in the gammaproteobacteriumEscherichia coliand for more moderate shifts between growth conditions. DksA modulates the expression of hundreds of genes, directly or indirectly. Mutants lacking a DksA homolog exhibit pleiotropic phenotypes in other gammaproteobacteria as well. Here we analyzed the DksA homolog RSP2654 in the more distantly relatedRhodobacter sphaeroides, an alphaproteobacterium. RSP2654 is 42% identical and similar in length toE. coliDksA but lacks the Zn finger motif of theE. coliDksA globular domain. Deletion of the RSP2654 gene results in defects in photosynthetic growth, impaired utilization of amino acids, and an increase in fatty acid content. RSP2654 complements the growth and regulatory defects of anE. colistrain lacking thedksAgene and modulates transcriptionin vitrowithE. coliRNA polymerase (RNAP) similarly toE. coliDksA. RSP2654 reduces RNAP-promoter complex stabilityin vitrowith RNAPs fromE. coliorR. sphaeroides, alone and synergistically with ppGpp, suggesting that even though it has limited sequence identity toE. coliDksA (DksAEc), it functions in a mechanistically similar manner. We therefore designate the RSP2654 protein DksARsp. Our work suggests that DksARsphas distinct and important physiological roles in alphaproteobacteria and will be useful for understanding structure-function relationships in DksA and the mechanism of synergy between DksA and ppGpp.IMPORTANCEThe role of DksA has been analyzed primarily in the gammaproteobacteria, in which it is best understood for its role in control of the synthesis of the translation apparatus and amino acid biosynthesis. Our work suggests that DksA plays distinct and important physiological roles in alphaproteobacteria, including the control of photosynthesis inRhodobacter sphaeroides. The study of DksARsp, should be useful for understanding structure-function relationships in the protein, including those that play a role in the little-understood synergy between DksA and ppGpp.

scholarly journals Activation of Toxin-Antitoxin System Toxins Suppresses Lethality Caused by the Loss of σEin Escherichia coli

2015 ◽  
Vol 197 (14) ◽  
pp. 2316-2324 ◽  
Author(s):  
Yasushi Daimon ◽  
Shin-ichiro Narita ◽  
Yoshinori Akiyama
Keyword(s):  
Escherichia Coli ◽  
Stress Responses ◽  
Ectopic Expression ◽  
Growth Media ◽  
Content Type ◽  
E Coli ◽  
Envelope Stress ◽  
Genes Encoding ◽  
Σ Factor ◽  
Mutant Forms

ABSTRACTσE, an alternative σ factor that governs a major signaling pathway in envelope stress responses in Gram-negative bacteria, is essential for growth ofEscherichia colinot only under stressful conditions, such as elevated temperature, but also under normal laboratory conditions. A mutational inactivation of thehicBgene has been reported to suppress the lethality caused by the loss of σE.hicBencodes the antitoxin of the HicA-HicB toxin-antitoxin (TA) system; overexpression of the HicA toxin, which exhibits mRNA interferase activity, causes cleavage of mRNAs and an arrest of cell growth, while simultaneous expression of HicB neutralizes the toxic effects of overproduced HicA. To date, however, how the loss of HicB rescues the cell lethality in the absence of σEand, more specifically, whether HicA is involved in this process remain unknown. Here we showed that simultaneous disruption ofhicAabolished suppression of the σEessentiality in the absence ofhicB, while ectopic expression of wild-type HicA, but not that of its mutant forms without mRNA interferase activity, restored the suppression. Furthermore, HicA and two other mRNA interferase toxins, HigB and YafQ, suppressed the σEessentiality even in the presence of chromosomally encoded cognate antitoxins when these toxins were overexpressed individually. Interestingly, when the growth media were supplemented with low levels of antibiotics that are known to activate toxins,E. colicells with no suppressor mutations grew independently of σE. Taken together, our results indicate that the activation of TA system toxins can suppress the σEessentiality and affect the extracytoplasmic stress responses.IMPORTANCEσEis an alternative σ factor involved in extracytoplasmic stress responses. Unlike other alternative σ factors, σEis indispensable for the survival ofE. colieven under unstressed conditions, although the exact reason for its essentiality remains unknown. Toxin-antitoxin (TA) systems are widely distributed in prokaryotes and are composed of two adjacent genes, encoding a toxin that exerts harmful effects on the toxin-producing bacterium itself and an antitoxin that neutralizes the cognate toxin. Curiously, it is known that inactivation of an antitoxin rescues the σEessentiality, suggesting a connection between TA systems and σEfunction. We demonstrate here that toxin activation is necessary for this rescue and suggest the possible involvement of TA systems in extracytoplasmic stress responses.

scholarly journals Heterogeneous and Flexible Transmission ofmcr-1in Hospital-AssociatedEscherichia coli

mBio ◽  
2018 ◽  
Vol 9 (4) ◽  
Author(s):  
Yingbo Shen ◽  
Zuowei Wu ◽  
Yang Wang ◽  
Rong Zhang ◽  
Hong-Wei Zhou ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Genomic Analysis ◽  
Multidrug Resistant ◽  
Fluoroquinolone Resistance ◽  
Gram Negative Bacteria ◽  
Colistin Resistance ◽  
Gram Negative ◽  
Content Type ◽  
E Coli ◽  
Genes Encoding

ABSTRACTThe recent emergence of a transferable colistin resistance mechanism, MCR-1, has gained global attention because of its threat to clinical treatment of infections caused by multidrug-resistant Gram-negative bacteria. However, the possible transmission route ofmcr-1amongEnterobacteriaceaespecies in clinical settings is largely unknown. Here, we present a comprehensive genomic analysis ofEscherichia coliisolates collected in a hospital in Hangzhou, China. We found thatmcr-1-carrying isolates from clinical infections and feces of inpatients and healthy volunteers were genetically diverse and were not closely related phylogenetically, suggesting that clonal expansion is not involved in the spread ofmcr-1. Themcr-1gene was found on either chromosomes or plasmids, but in most of theE. coliisolates,mcr-1was carried on plasmids. The genetic context of the plasmids showed considerable diversity as evidenced by the different functional insertion sequence (IS) elements, toxin-antitoxin (TA) systems, heavy metal resistance determinants, and Rep proteins of broad-host-range plasmids. Additionally, the genomic analysis revealed nosocomial transmission ofmcr-1and the coexistence ofmcr-1with other genes encoding β-lactamases and fluoroquinolone resistance in theE. coliisolates. These findings indicate thatmcr-1is heterogeneously disseminated in both commensal and pathogenic strains ofE. coli, suggest the high flexibility of this gene in its association with diverse genetic backgrounds of the hosts, and provide new insights into the genome epidemiology ofmcr-1among hospital-associatedE. colistrains.IMPORTANCEColistin represents one of the very few available drugs for treating infections caused by extensively multidrug-resistant Gram-negative bacteria. The recently emergentmcr-1colistin resistance gene threatens the clinical utility of colistin and has gained global attention. Howmcr-1spreads in hospital settings remains unknown and was investigated by whole-genome sequencing ofmcr-1-carryingEscherichia coliin this study. The findings revealed extraordinary flexibility ofmcr-1in its spread among genetically diverseE. colihosts and plasmids, nosocomial transmission ofmcr-1-carryingE. coli, and the continuous emergence of novel Inc types of plasmids carryingmcr-1and newmcr-1variants. Additionally,mcr-1was found to be frequently associated with other genes encoding β-lactams and fluoroquinolone resistance. These findings provide important information on the transmission and epidemiology ofmcr-1and are of significant public health importance as the information is expected to facilitate the control of this significant antibiotic resistance threat.

scholarly journals Characterization of Multidrug-Resistant Escherichia coli Isolates from Animals Presenting at a University Veterinary Hospital

2011 ◽  
Vol 77 (20) ◽  
pp. 7104-7112 ◽  
Author(s):  
Maria Karczmarczyk ◽  
Yvonne Abbott ◽  
Ciara Walsh ◽  
Nola Leonard ◽  
Séamus Fanning
Keyword(s):  
Escherichia Coli ◽  
Molecular Mechanisms ◽  
Gene Array ◽  
Multidrug Resistant ◽  
Genetic Determinants ◽  
Gene Encoding ◽  
Content Type ◽  
E Coli ◽  
Class 1

ABSTRACTIn this study, we examined molecular mechanisms associated with multidrug resistance (MDR) in a collection ofEscherichia coliisolates recovered from hospitalized animals in Ireland. PCR and DNA sequencing were used to identify genes associated with resistance. Class 1 integrons were prevalent (94.6%) and contained gene cassettes recognized previously and implicated mainly in resistance to aminoglycosides, β-lactams, and trimethoprim (aadA1,dfrA1-aadA1,dfrA17-aadA5,dfrA12-orfF-aadA2,blaOXA-30-aadA1,aacC1-orf1-orf2-aadA1,dfr7). Class 2 integrons (13.5%) contained thedfrA1-sat1-aadA1gene array. The most frequently occurring phenotypes included resistance to ampicillin (97.3%), chloramphenicol (75.4%), florfenicol (40.5%), gentamicin (54%), neomycin (43.2%), streptomycin (97.3%), sulfonamide (98.6%), and tetracycline (100%). The associated resistance determinants detected includedblaTEM,cat,floR,aadB,aphA1,strA-strB,sul2, andtet(B), respectively. TheblaCTX-M-2gene, encoding an extended-spectrum β-lactamase (ESβL), andblaCMY-2, encoding an AmpC-like enzyme, were identified in 8 and 18 isolates, respectively. The mobility of the resistance genes was demonstrated using conjugation assays with a representative selection of isolates. High-molecular-weight plasmids were found to be responsible for resistance to multiple antimicrobial compounds. The study demonstrated that animal-associated commensalE. coliisolates possess a diverse repertoire of transferable genetic determinants. Emergence of ESβLs and AmpC-like enzymes is particularly significant. To our knowledge, theblaCTX-M-2gene has not previously been reported in Ireland.

scholarly journals Variations in O-Antigen Biosynthesis and O-Acetylation Associated with Altered Phage Sensitivity in Escherichia coli 4s

2014 ◽  
Vol 197 (5) ◽  
pp. 905-912 ◽  
Author(s):  
Yuriy A. Knirel ◽  
Nikolai S. Prokhorov ◽  
Alexander S. Shashkov ◽  
Olga G. Ovchinnikova ◽  
Evelina L. Zdorovenko ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Host Cells ◽  
Side Chain ◽  
Gram Negative Bacteria ◽  
Gene Encoding ◽  
Content Type ◽  
Surface Receptors ◽  
E Coli ◽  
O Antigen ◽  
Phage Sensitivity

The O polysaccharide of the lipopolysaccharide (O antigen) of Gram-negative bacteria often serves as a receptor for bacteriophages that can make the phage dependent on a given O-antigen type, thus supporting the concept of the adaptive significance of the O-antigen variability in bacteria. The O-antigen layer also modulates interactions of many bacteriophages with their hosts, limiting the access of the viruses to other cell surface receptors. Here we report variations of O-antigen synthesis and structure in an environmentalEscherichia coliisolate, 4s, obtained from horse feces, and its mutants selected for resistance to bacteriophage G7C, isolated from the same fecal sample. The 4s O antigen was found to be serologically, structurally, and genetically related to the O antigen ofE. coliO22, differing only in side-chain α-d-glucosylation in the former, mediated by agtrlocus on the chromosome. Spontaneous mutations ofE. coli4s occurring with an unusually high frequency affected either O-antigen synthesis or O-acetylation due to the inactivation of the gene encoding the putative glycosyltransferase WclH or the putative acetyltransferase WclK, respectively, by the insertion of IS1-like elements. These mutations induced resistance to bacteriophage G7C and also modified interactions ofE. coli4s with several other bacteriophages conferring either resistance or sensitivity to the host. These findings suggest that O-antigen synthesis and O-acetylation can both ensure the specific recognition of the O-antigen receptor following infection by some phages and provide protection of the host cells against attack by other phages.

scholarly journals Dynamic Mechanisms of the Bactericidal Action of an Al2O3-TiO2-Ag Granular Material on an Escherichia coli Strain

2015 ◽  
Vol 81 (20) ◽  
pp. 7135-7142 ◽  
Author(s):  
Marie-Anne Tartanson ◽  
Laurence Soussan ◽  
Matthieu Rivallin ◽  
Sophie Pecastaings ◽  
Cristian V. Chis ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Granular Material ◽  
Morphological Changes ◽  
Membrane Damage ◽  
Coli Strain ◽  
Cell Integrity ◽  
Bactericidal Action ◽  
Intact Cells ◽  
Content Type ◽  
E Coli

ABSTRACTThe bactericidal activity of an Al2O3-TiO2-Ag granular material against anEscherichia colistrain was confirmed by a culture-based method. In particular, 100% of microorganisms were permanently inactivated in 30 to 45 min. The present work aimed to investigate the mechanisms of the bactericidal action of this material and their dynamics onEscherichia coliusing different techniques. Observations by transmission electron microscopy (TEM) at different times of disinfection revealed morphological changes in the bacteria as soon as they were put in contact with the material. Notably highlighted were cell membrane damage; cytoplasm detachment; formation of vacuoles, possibly due to DNA condensation, in association with regions exhibiting different levels of electron density; and membrane lysis. PCR and flow cytometry analyses were used to confirm and quantify the observations of cell integrity. The direct exposure of cells to silver, combined with the oxidative stress induced by the reactive oxygen species (ROS) generated, was identified to be responsible for these morphological alterations. From the first 5 min of treatment with the Al2O3-TiO2-Ag material, 98% ofE. coliisolates were lysed. From 30 min, cell viability decreased to reach total inactivation, although approximately 1% of permeableE. colicells and 1% of intact cells (105genomic units · ml−1) were evidenced. This study demonstrates that the bactericidal effect of the material results from a synergic action of desorbed and supported silver. Supported silver was shown to generate the ROS evidenced.

scholarly journals Transcriptional Regulation of theecpOperon by EcpR, IHF, and H-NS in Attaching and Effacing Escherichia coli

2012 ◽  
Vol 194 (18) ◽  
pp. 5020-5033 ◽  
Author(s):  
Verónica I. Martínez-Santos ◽  
Abraham Medrano-López ◽  
Zeus Saldaña ◽  
Jorge A. Girón ◽  
José L. Puente
Keyword(s):  
Escherichia Coli ◽  
Transcriptional Regulation ◽  
Dna Binding ◽  
Regulatory Protein ◽  
Integration Host Factor ◽  
Start Codon ◽  
Binding Motif ◽  
Epithelial Surface ◽  
Content Type ◽  
E Coli

ABSTRACTEnteropathogenic (EPEC) and enterohemorrhagic (EHEC)Escherichia coliare clinically important diarrheagenic pathogens that adhere to the intestinal epithelial surface. TheE. colicommon pili (ECP), or meningitis-associated and temperature-regulated (MAT) fimbriae, are ubiquitous among both commensal and pathogenicE. colistrains and play a role as colonization factors by promoting the interaction between bacteria and host epithelial cells and favoring interbacterial interactions in biofilm communities. The first gene of theecpoperon encodes EcpR (also known as MatA), a proposed regulatory protein containing a LuxR-like C-terminal helix-turn-helix (HTH) DNA-binding motif. In this work, we analyzed the transcriptional regulation of theecpgenes and the role of EcpR as a transcriptional regulator. EHEC and EPECecpRmutants produce less ECP, while plasmids expressing EcpR increase considerably the expression of EcpA and production of ECP. Theecpgenes are transcribed as an operon from a promoter located 121 bp upstream of the start codon ofecpR. EcpR positively regulates this promoter by binding to two TTCCT boxes distantly located upstream of theecppromoter, thus enhancing expression of downstreamecpgenes, leading to ECP production. EcpR mutants in the putative HTH DNA-binding domain are no longer able to activateecpexpression or bind to the TTCCT boxes. EcpR-mediated activation is aided by integration host factor (IHF), which is essential for counteracting the repression exerted by histone-like nucleoid-structuring protein (H-NS) on theecppromoter. This work demonstrates evidence about the interplay between a novel member of a diverse family of regulatory proteins and global regulators in the regulation of a fimbrial operon.

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