scholarly journals Evolutionary Silence of the Acid Chaperone Protein HdeB in Enterohemorrhagic Escherichia coli O157:H7

2011 ◽  
Vol 78 (4) ◽  
pp. 1004-1014 ◽  
Author(s):  
Michelle Q. Carter ◽  
Jacqueline W. Louie ◽  
Clifton K. Fagerquist ◽  
Omar Sultan ◽  
William G. Miller ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acid Resistance ◽  
Significant Loss ◽  
Enterohemorrhagic Escherichia Coli ◽  
Survival Strategies ◽  
Start Codon ◽  
Divergent Evolution ◽  
Content Type ◽  
E Coli ◽  
K 12

ABSTRACTThe periplasmic chaperones HdeA and HdeB are known to be important for cell survival at low pH (pH < 3) inEscherichia coliandShigellaspp. Here we investigated the roles of HdeA and HdeB in the survival of various enterohemorrhagicE. coli(EHEC) following exposure to pH 2.0. Similar to K-12 strains, the acid protections conferred by HdeA and HdeB in EHEC O145 were significant: loss of HdeA and HdeB led to over 100- to 1,000-fold reductions in acid survival, depending on the growth condition of prechallenge cells. However, this protection was much less inE. coliO157:H7 strains. Deletion ofhdeBdid not affect the acid survival of cells, and deletion ofhdeAled to less than a 5-fold decrease in survival. Sequence analysis of thehdeABoperon revealed a point mutation at the putative start codon of thehdeBgene in all 26E. coliO157:H7 strains analyzed, which shifted the ATG start codon to ATA. This mutation correlated with the lack of HdeB inE. coliO157:H7; however, the plasmid-borne O157-hdeBwas able to restore partially the acid resistance in anE. coliO145ΔhdeABmutant, suggesting the potential function of O157-HdeB as an acid chaperone. We conclude thatE. coliO157:H7 strains have evolved acid survival strategies independent of the HdeA/B chaperones and are more acid resistant than nonpathogenic K-12 for cells grown under nonfavorable culturing conditions such as in Luria-Bertani no-salt broth at 28°C. These results suggest a divergent evolution of acid resistance mechanisms withinE. coli.

scholarly journals Global Analysis of Posttranscriptional Regulation by GlmY and GlmZ in Enterohemorrhagic Escherichia coli O157:H7

2015 ◽  
Vol 83 (4) ◽  
pp. 1286-1295 ◽  
Author(s):  
Charley C. Gruber ◽  
Vanessa Sperandio
Keyword(s):  
Escherichia Coli ◽  
Rna Sequencing ◽  
Posttranscriptional Regulation ◽  
Global Analysis ◽  
Acid Resistance ◽  
Enterohemorrhagic Escherichia Coli ◽  
Global Changes ◽  
Content Type ◽  
Enterocyte Effacement ◽  
K 12

EnterohemorrhagicEscherichia coli(EHEC) is a significant human pathogen and is the cause of bloody diarrhea and hemolytic-uremic syndrome. The virulence repertoire of EHEC includes the genes within the locus of enterocyte effacement (LEE) that are largely organized in five operons,LEE1toLEE5, which encode a type III secretion system, several effectors, chaperones, and regulatory proteins. In addition, EHEC also encodes several non-LEE-encoded effectors and fimbrial operons. The virulence genes of this pathogen are under a large amount of posttranscriptional regulation. The small RNAs (sRNAs) GlmY and GlmZ activate the translation of glucosamine synthase (GlmS) inE. coliK-12, and in EHEC they destabilize the 3′ fragments of theLEE4andLEE5operons and promote translation of the non-LEE-encoded effector EspFu. We investigated the global changes of EHEC gene expression governed by GlmY and GlmZ using RNA sequencing and gene arrays. This study extends the known effects of GlmY and GlmZ regulation to show that they promote expression of the curli adhesin, repress the expression of tryptophan metabolism genes, and promote the expression of acid resistance genes and the non-LEE-encoded effector NleA. In addition, seven novel EHEC-specific sRNAs were identified using RNA sequencing, and three of them—sRNA56, sRNA103, and sRNA350—were shown to regulate urease, fimbria, and the LEE, respectively. These findings expand the knowledge of posttranscriptional regulation in EHEC.

scholarly journals Distinct Acid Resistance and Survival Fitness Displayed by Curli Variants of Enterohemorrhagic Escherichia coli O157:H7

2011 ◽  
Vol 77 (11) ◽  
pp. 3685-3695 ◽  
Author(s):  
Michelle Q. Carter ◽  
Maria T. Brandl ◽  
Jacqueline W. Louie ◽  
Jennifer L. Kyle ◽  
Diana K. Carychao ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acid Resistance ◽  
Cell Aggregation ◽  
Oxygen Depletion ◽  
Growth Conditions ◽  
Enterohemorrhagic Escherichia Coli ◽  
Surface Attachment ◽  
Content Type ◽  
E Coli ◽  
Physiological Properties

ABSTRACTCurli are adhesive fimbriae ofEnterobacteriaceaeand are involved in surface attachment, cell aggregation, and biofilm formation. Here, we report that both inter- and intrastrain variations in curli production are widespread in enterohemorrhagicEscherichia coliO157:H7. The relative proportions of curli-producing variants (C+) and curli-deficient variants (C−) in anE. coliO157:H7 cell population varied depending on the growth conditions. In variants derived from the 2006 U.S. spinach outbreak strains, the shift between the C+and C−subpopulations occurred mostly in response to starvation and was unidirectional from C−to C+; in variants derived from the 1993 hamburger outbreak strains, the shift occurred primarily in response to oxygen depletion and was bidirectional. Furthermore, curli variants derived from the same strain displayed marked differences in survival fitness: C+variants grew to higher concentrations in nutrient-limited conditions than C−variants, whereas C−variants were significantly more acid resistant than C+variants. This difference in acid resistance does not appear to be linked to the curli fimbriaeper se, since acsgAdeletion mutant in either a C+or a C−variant exhibited an acid resistance similar to that of its parental strain. Our data suggest that natural curli variants ofE. coliO157:H7 carry several distinct physiological properties that are important for their environmental survival. Maintenance of curli variants in anE. coliO157:H7 population may provide a survival strategy in which C+variants are selected in a nutrient-limited environment, whereas C−variants are selected in an acidic environment, such as the stomach of an animal host, including that of a human.

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 The Small Noncoding DsrA RNA Is an Acid Resistance Regulator in Escherichia coli

2004 ◽  
Vol 186 (18) ◽  
pp. 6179-6185 ◽  
Author(s):  
Richard A. Lease ◽  
Dorie Smith ◽  
Kathleen McDonough ◽  
Marlene Belfort
Keyword(s):  
Escherichia Coli ◽  
Stress Response ◽  
Resistance Genes ◽  
Acid Resistance ◽  
Dna Arrays ◽  
E Coli ◽  
Specific Mrnas ◽  
Steady State Levels ◽  
Control Translation ◽  
K 12

ABSTRACT DsrA RNA is a small (87-nucleotide) regulatory RNA of Escherichia coli that acts by RNA-RNA interactions to control translation and turnover of specific mRNAs. Two targets of DsrA regulation are RpoS, the stationary-phase and stress response sigma factor (σs), and H-NS, a histone-like nucleoid protein and global transcription repressor. Genes regulated globally by RpoS and H-NS include stress response proteins and virulence factors for pathogenic E. coli. Here, by using transcription profiling via DNA arrays, we have identified genes induced by DsrA. Steady-state levels of mRNAs from many genes increased with DsrA overproduction, including multiple acid resistance genes of E. coli. Quantitative primer extension analysis verified the induction of individual acid resistance genes in the hdeAB, gadAX, and gadBC operons. E. coli K-12 strains, as well as pathogenic E. coli O157:H7, exhibited compromised acid resistance in dsrA mutants. Conversely, overproduction of DsrA from a plasmid rendered the acid-sensitive dsrA mutant extremely acid resistant. Thus, DsrA RNA plays a regulatory role in acid resistance. Whether DsrA targets acid resistance genes directly by base pairing or indirectly via perturbation of RpoS and/or H-NS is not known, but in either event, our results suggest that DsrA RNA may enhance the virulence of pathogenic E. coli.

scholarly journals Antibiotic-Mediated Modulations of Outer Membrane Vesicles in Enterohemorrhagic Escherichia coli O104:H4 and O157:H7

2017 ◽  
Vol 61 (9) ◽  
Author(s):  
Andreas Bauwens ◽  
Lisa Kunsmann ◽  
Helge Karch ◽  
Alexander Mellmann ◽  
Martina Bielaszewska
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Shiga Toxin ◽  
Membrane Vesicles ◽  
Polymyxin B ◽  
Outer Membrane Vesicles ◽  
Enterohemorrhagic Escherichia Coli ◽  
Content Type ◽  
E Coli ◽  
Major Virulence Factor

ABSTRACT Ciprofloxacin, meropenem, fosfomycin, and polymyxin B strongly increase production of outer membrane vesicles (OMVs) in Escherichia coli O104:H4 and O157:H7. Ciprofloxacin also upregulates OMV-associated Shiga toxin 2a, the major virulence factor of these pathogens, whereas the other antibiotics increase OMV production without the toxin. These two effects might worsen the clinical outcome of infections caused by Shiga toxin-producing E. coli. Our data support the existing recommendations to avoid antibiotics for treatment of these infections.

scholarly journals Molecular Control of Sucrose Utilization in Escherichia coli W, an Efficient Sucrose-Utilizing Strain

2012 ◽  
Vol 79 (2) ◽  
pp. 478-487 ◽  
Author(s):  
Suriana Sabri ◽  
Lars K. Nielsen ◽  
Claudia E. Vickers
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Good Growth ◽  
Knockout Mutant ◽  
Sucrose Transport ◽  
Molecular Control ◽  
Content Type ◽  
E Coli ◽  
K 12 ◽  
Sucrose Utilization

ABSTRACTSucrose is an industrially important carbon source for microbial fermentation. Sucrose utilization inEscherichia coli, however, is poorly understood, and most industrial strains cannot utilize sucrose. The roles of the chromosomally encoded sucrose catabolism (csc) genes inE. coliW were examined by knockout and overexpression experiments. At low sucrose concentrations, thecscgenes are repressed and cells cannot grow. Removal of either the repressor protein (cscR) or the fructokinase (cscK) gene facilitated derepression. Furthermore, combinatorial knockout ofcscRandcscKconferred an improved growth rate on low sucrose. The invertase (cscA) and sucrose transporter (cscB) genes are essential for sucrose catabolism inE. coliW, demonstrating that no other genes can provide sucrose transport or inversion activities. However,cscKis not essential for sucrose utilization. Fructose is excreted into the medium by thecscK-knockout strain in the presence of high sucrose, whereas at low sucrose (when carbon availability is limiting), fructose is utilized by the cell. Overexpression ofcscA,cscAK, orcscABcould complement the WΔcscRKABknockout mutant or confer growth on a K-12 strain which could not naturally utilize sucrose. However, phenotypic stability and relatively good growth rates were observed in the K-12 strain only when overexpressingcscAB, and full growth rate complementation in WΔcscRKABalso requiredcscAB. Our understanding of sucrose utilization can be used to improveE. coliW and engineer sucrose utilization in strains which do not naturally utilize sucrose, allowing substitution of sucrose for other, less desirable carbon sources in industrial fermentations.

scholarly journals Increased Survival of Antibiotic-Resistant Escherichia coli inside Macrophages

2012 ◽  
Vol 57 (1) ◽  
pp. 189-195 ◽  
Author(s):  
Migla Miskinyte ◽  
Isabel Gordo
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Bacterial Infections ◽  
Resistance Mutation ◽  
Fitness Cost ◽  
Resistance Mutations ◽  
Content Type ◽  
E Coli ◽  
Fitness Effects ◽  
K 12

ABSTRACTMutations causing antibiotic resistance usually incur a fitness cost in the absence of antibiotics. The magnitude of such costs is known to vary with the environment. Little is known about the fitness effects of antibiotic resistance mutations when bacteria confront the host's immune system. Here, we study the fitness effects of mutations in therpoB,rpsL, andgyrAgenes, which confer resistance to rifampin, streptomycin, and nalidixic acid, respectively. These antibiotics are frequently used in the treatment of bacterial infections. We measured two important fitness traits—growth rate and survival ability—of 12Escherichia coliK-12 strains, each carrying a single resistance mutation, in the presence of macrophages. Strikingly, we found that 67% of the mutants survived better than the susceptible bacteria in the intracellular niche of the phagocytic cells. In particular, allE. colistreptomycin-resistant mutants exhibited an intracellular advantage. On the other hand, 42% of the mutants incurred a high fitness cost when the bacteria were allowed to divide outside of macrophages. This study shows that single nonsynonymous changes affecting fundamental processes in the cell can contribute to prolonged survival ofE. coliin the context of an infection.

scholarly journals Bioinformatic and Molecular Analysis of Inverse Autotransporters from Escherichia coli

mSphere ◽  
2019 ◽  
Vol 4 (4) ◽  
Author(s):  
Kelvin G. K. Goh ◽  
Danilo G. Moriel ◽  
Steven J. Hancock ◽  
Minh-Duy Phan ◽  
Mark A. Schembri
Keyword(s):  
Escherichia Coli ◽  
Cell Surface ◽  
Biofilm Formation ◽  
Secretion System ◽  
Content Type ◽  
E Coli ◽  
Wide Range ◽  
Type V Secretion ◽  
K 12 ◽  
Type V

ABSTRACT Proteins secreted by the type V secretion system possess multiple functions, including the capacity to mediate adhesion, aggregation, and biolfilm formation. The type V secretion system can be divided into five subclasses, one of which is the type Ve system. Proteins of the type Ve secretion system are also referred to as inverse autotransporters (IATs). In this study, we performed an in silico analysis of 126 completely sequenced Escherichia coli genomes available in the NCBI database and identified several distinct IAT-encoding gene families whose distribution varied throughout the E. coli phylogeny. The genes included three characterized IATs (intimin, fdeC, and yeeJ) and four uncharacterized IATs (here named iatA, iatB, iatC, and iatD). The four iat genes were cloned from the completely sequenced environmental E. coli strain SMS-3-5 and characterized. Three of these IAT proteins (IatB, IatC, and IatD) were expressed at the cell surface and possessed the capacity to mediate biofilm formation in a recombinant E. coli K-12 strain. Further analysis of the iatB gene, which showed a unique association with extraintestinal E. coli strains, suggested that its regulation is controlled by the LeuO global regulator. Overall, this study provides new data describing the prevalence, sequence variation, domain structure, function, and regulation of IATs found in E. coli. IMPORTANCE Escherichia coli is one of the most prevalent facultative anaerobes of the human gut. E. coli normally exists as a harmless commensal but can also cause disease following the acquisition of genes that enhance its pathogenicity. Adhesion is an important first step in colonization of the host and is mediated by an array of cell surface components. In E. coli, these include a family of adhesins secreted by the type V secretion system. Here, we identified and characterized new proteins from an emerging subclass of the type V secretion system known as the inverse autotransporters (IATs). We found that IAT-encoding genes are present in a wide range of strains and showed that three novel IATs were localized on the E. coli cell surface and mediated biofilm formation. Overall, this study provides new insight into the prevalence, function, and regulation of IATs in E. coli.

scholarly journals Fitness of Enterohemorrhagic Escherichia coli (EHEC)/Enteroaggregative E. coli O104:H4 in Comparison to That of EHEC O157: Survival Studies in Food andIn Vitro

2016 ◽  
Vol 82 (21) ◽  
pp. 6326-6334 ◽  
Author(s):  
Christina Böhnlein ◽  
Jan Kabisch ◽  
Diana Meske ◽  
Charles M. A. P. Franz ◽  
Rohtraud Pichner
Keyword(s):  
Escherichia Coli ◽  
Meat Product ◽  
Enterohemorrhagic Escherichia Coli ◽  
Content Type ◽  
E Coli ◽  
Adverse Conditions ◽  
Log Reduction ◽  
Fermented Sausages ◽  
Survival Studies

ABSTRACTIn 2011, one of the world's largest outbreaks of hemolytic-uremic syndrome (HUS) occurred, caused by a rareEscherichia coliserotype, O104:H4, that shared the virulence profiles of Shiga toxin-producingE. coli(STEC)/enterohemorrhagicE. coli(EHEC) and enteroaggregativeE. coli(EAEC). The persistence and fitness factors of the highly virulent EHEC/EAEC O104:H4 strain, grown either in food orin vitro, were compared with those ofE. coliO157 outbreak-associated strains. The log reduction rates of the different EHEC strains during the maturation of fermented sausages were not significantly different. Both the O157:NM and O104:H4 serotypes could be shown by qualitative enrichment to be present after 60 days of sausage storage. Moreover, the EHEC/EAEC O104:H4 strain appeared to be more viable thanE. coliO157:H7 under conditions of decreased pH and in the presence of sodium nitrite. Analysis of specific EHEC strains in experiments with an EHEC inoculation cocktail showed a dominance of EHEC/EAEC O104:H4, which could be isolated from fermented sausages for 60 days. Inhibitory activities of EHEC/EAEC O104:H4 toward severalE. colistrains, including serotype O157 strains, could be determined. Our study suggests that EHEC/EAEC O104:H4 is well adapted to the multiple adverse conditions occurring in fermented raw sausages. Therefore, it is strongly recommended that STEC strain cocktails composed of several serotypes, instead ofE. coliO157:H7 alone, be used in food risk assessments. The enhanced persistence of EHEC/EAEC O104:H4 as a result of its robustness, as well as the production of bacteriocins, may account for its extraordinary virulence potential.IMPORTANCEIn 2011, a severe outbreak caused by an EHEC/EAEC serovar O104:H4 strain led to many HUS sequelae. In this study, the persistence of the O104:H4 strain was compared with those of other outbreak-relevant STEC strains under conditions of fermented raw sausage production. Both O157:NM and O104:H4 strains could survive longer during the production of fermented sausages thanE. coliO157:H7 strains.E. coliO104:H4 was also shown to be well adapted to the multiple adverse conditions encountered in fermented sausages, and the secretion of a bacteriocin may explain the competitive advantage of this strain in an EHEC strain cocktail. Consequently, this study strongly suggests that enhanced survival and persistence, and the presumptive production of a bacteriocin, may explain the increased virulence of the O104:H4 outbreak strain. Furthermore, this strain appears to be capable of surviving in a meat product, suggesting that meat should not be excluded as a source of potentialE. coliO104:H4 infection.

scholarly journals Global Regulator of Virulence A (GrvA) Coordinates Expression of Discrete Pathogenic Mechanisms in Enterohemorrhagic Escherichia coli through Interactions with GadW-GadE

2015 ◽  
Vol 198 (3) ◽  
pp. 394-409 ◽  
Author(s):  
Jason K. Morgan ◽  
Ronan K. Carroll ◽  
Carly M. Harro ◽  
Khoury W. Vendura ◽  
Lindsey N. Shaw ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acid Resistance ◽  
Enterohemorrhagic Escherichia Coli ◽  
Sequencing Analysis ◽  
Global Regulator ◽  
Altered Expression ◽  
Content Type ◽  
Pathogenic Mechanisms ◽  
Gut Colonization ◽  
Intestinal Pathogens

ABSTRACTGlobal regulator of virulence A (GrvA) is a ToxR-family transcriptional regulator that activates locus of enterocyte effacement (LEE)-dependent adherence in enterohemorrhagicEscherichia coli(EHEC). LEE activation by GrvA requires the Rcs phosphorelay response regulator RcsB and is sensitive to physiologically relevant concentrations of bicarbonate, a known stimulant of virulence systems in intestinal pathogens. This study determines the genomic scale of GrvA-dependent regulation and uncovers details of the molecular mechanism underlying GrvA-dependent regulation of pathogenic mechanisms in EHEC. In agrvA-null background of EHEC strain TW14359, RNA sequencing analysis revealed the altered expression of over 700 genes, including the downregulation of LEE- and non-LEE-encoded effectors and the upregulation of genes for glutamate-dependent acid resistance (GDAR). Upregulation of GDAR genes corresponded with a marked increase in acid resistance. GrvA-dependent regulation of GDAR and the LEE requiredgadE, the central activator of GDAR genes and a direct repressor of the LEE. Control ofgadEby GrvA was further determined to occur through downregulation of thegadEactivator GadW. This interaction of GrvA with GadW-GadE represses the acid resistance phenotype, while it concomitantly activates the LEE-dependent adherence and secretion of immune subversion effectors. The results of this study significantly broaden the scope of GrvA-dependent regulation and its role in EHEC pathogenesis.IMPORTANCEEnterohemorrhagicEscherichia coli(EHEC) is an intestinal human pathogen causing acute hemorrhagic colitis and life-threatening hemolytic-uremic syndrome. For successful transmission and gut colonization, EHEC relies on the glutamate-dependent acid resistance (GDAR) system and a type III secretion apparatus, encoded on the LEE pathogenicity island. This study investigates the mechanism whereby the DNA-binding regulator GrvA coordinates activation of the LEE with repression of GDAR. Investigating how these systems are regulated leads to an understanding of pathogenic behavior and novel strategies aimed at disease prevention and control.

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