scholarly journals Role of Escherichia coli O157:H7 Virulence Factors in Colonization at the Bovine Terminal Rectal Mucosa

2006 ◽  
Vol 74 (8) ◽  
pp. 4685-4693 ◽  
Author(s):  
Haiqing Sheng ◽  
Ji Youn Lim ◽  
Hannah J. Knecht ◽  
Jie Li ◽  
Carolyn J. Hovde
Keyword(s):  
Escherichia Coli ◽  
Virulence Factors ◽  
Clinical Manifestations ◽  
Rectal Mucosa ◽  
Wild Type ◽  
E Coli ◽  
Healthy Cattle ◽  
Life Threatening ◽  
K 12 ◽  
The Impact

ABSTRACT The human pathogen Escherichia coli O157:H7 causes hemorrhagic colitis and life-threatening sequelae and transiently colonizes healthy cattle at the terminal rectal mucosa. This study analyzed virulence factors important for the clinical manifestations of human E. coli O157:H7 infection for their contribution to the persistence of E. coli in cattle. The colonizing ability of E. coli O157:H7 was compared with those of nonpathogenic E. coli K-12 and isogenic deletion mutants missing Shiga toxin (Stx), the adhesin intimin, its receptor Tir, hemolysin, or the ∼92-kb pO157. Fully ruminant steers received a single rectal application of one E. coli strain so that effects of mucosal attachment and survival at the terminal rectum could be measured without the impact of bacterial passage through the entire gastrointestinal tract. Colonization was monitored by sensitive recto-anal junction mucosal swab culture. Nonpathogenic E. coli K-12 did not colonize as well as E. coli O157:H7 at the bovine terminal rectal mucosa. The E. coli O157:H7 best able to persist had intimin, Tir, and the pO157. Strains missing even one of these factors were recovered in lower numbers and were cleared faster than the wild type. In contrast, E. coli O157:H7 strains that were missing Stx or hemolysin colonized like the wild type. For these three strains, the number of bacteria increased between days 1 and 4 postapplication and then decreased slowly. In contrast, the numbers of noncolonizing strains (K-12, Δtir, and Δeae) decreased from the day of application. These patterns consistently predicted long-term colonization or clearance of the bacteria from the bovine terminal rectal mucosa.

scholarly journals First-Time Isolation and Characterization of a Bacteriophage Encoding the Shiga Toxin 2c Variant, Which Is Globally Spread in Strains of Escherichia coli O157

2004 ◽  
Vol 72 (12) ◽  
pp. 7030-7039 ◽  
Author(s):  
Eckhard Strauch ◽  
Christoph Schaudinn ◽  
Lothar Beutin
Keyword(s):  
Escherichia Coli ◽  
Shiga Toxin ◽  
Phage Lambda ◽  
Wild Type ◽  
Chromosomal Locus ◽  
O157 Strain ◽  
Diagnostic Pcr ◽  
E Coli ◽  
Isolation And Characterization ◽  
K 12

ABSTRACT A bacteriophage encoding the Shiga toxin 2c variant (Stx2c) was isolated from the human Escherichia coli O157 strain CB2851 and shown to form lysogens on the E. coli K-12 laboratory strains C600 and MG1655. Production of Stx2c was found in the wild-type E. coli O157 strain and the K-12 lysogens and was inducible by growing bacteria in the presence of ciprofloxacin. Phage 2851 is the first reported viable bacteriophage which carries an stx 2c gene. Electron micrographs of phage 2851 showed particles with elongated hexagonal heads and long flexible tails resembling phage lambda. Sequence analysis of an 8.4-kb region flanking the stx 2c gene and other genetic elements revealed a mosaic gene structure, as found in other Stx phages. Phage 2851 showed lysis of E. coli K-12 strains lysogenic for Stx phages encoding Stx1 (H19), Stx2 (933W), Stx (7888), and Stx1c (6220) but showed superinfection immunity with phage lambda, presumably originating from the similarity of the cI repressor proteins of both phages. Apparently, phage 2851 integrates at a different chromosomal locus than Stx2 phage 933W and Stx1 phage H19 in E. coli, explaining why Stx2c is often found in combination with Stx1 or Stx2 in E. coli O157 strains. Diagnostic PCR was performed to determine gene sequences specific for phage 2851 in wild-type E. coli O157 strains producing Stx2c. The phage 2851 q and o genes were frequently detected in Stx2c-producing E. coli O157 strains, indicating that phages related to 2851 are associated with Stx2c production in strains of E. coli O157 that were isolated in different locations and time periods.

scholarly journals Complete Genome Sequence of the Engineered Escherichia coli SHuffle Strains and Their Wild-Type Parents

2016 ◽  
Vol 4 (2) ◽  
Author(s):  
Brian P. Anton ◽  
Alexey Fomenkov ◽  
Elisabeth A. Raleigh ◽  
Mehmet Berkmen
Keyword(s):  
Escherichia Coli ◽  
Complete Genome ◽  
Disulfide Bonds ◽  
Scientific Community ◽  
Genetically Engineered ◽  
Wild Type ◽  
E Coli ◽  
Biotech Industry ◽  
General Scientific ◽  
K 12

SHuffle strains are genetically engineered Escherichia coli strains that are capable of oxidizing cysteines within proteins to form disulfide bonds. Here we present the complete genome of both the K-12 and B versions of SHuffle strains along with their parental ancestors. These strains have been of significant use to both the general scientific community and the biotech industry, interested in producing novel disulfide-bonded proteins that were hitherto unable to be expressed in standard E. coli expression strains.

A new method for the isolation of methionyl transfer RNA synthetase mutants from Escherichia coli

1975 ◽  
Vol 21 (6) ◽  
pp. 754-758 ◽  
Author(s):  
John B. Armstrong ◽  
John A. Fairfield
Keyword(s):  
Escherichia Coli ◽  
Trna Synthetase ◽  
Transfer Rna ◽  
New Method ◽  
Wild Type ◽  
E Coli ◽  
Adenosyl Methionine ◽  
K 12 ◽  
Methionyl Trna Synthetase

Six methionine auxotrophs were isolated from an E. coli K-12 strain which required up to 100 times as much methionine for growth as a conventional auxotroph. In these mutants, the methionyl-tRNA synthetase had an increased Km for methionine. The Km value for the mutants ranged from 0.48 to 1.63 mM, compared to 0.078 mM for the wild type. The Km (methionine) for S-adenosyl methionine synthetase was not altered.

scholarly journals Cloning, Expression, and Characterization of Fimbrial Operon F9 from Enterohemorrhagic Escherichia coli O157:H7

2006 ◽  
Vol 74 (4) ◽  
pp. 2233-2244 ◽  
Author(s):  
Alison S. Low ◽  
Francis Dziva ◽  
Alfredo G. Torres ◽  
Jessenya L. Martinez ◽  
Tracy Rosser ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Epithelial Cells ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Enterohemorrhagic Escherichia Coli ◽  
Wild Type ◽  
Induced Expression ◽  
E Coli ◽  
Extracellular Matrix Components ◽  
K 12

ABSTRACT Recent transposon mutagenesis studies with two enterohemorrhagic Escherichia coli (EHEC) strains, a sero- type O26:H- strain and a serotype O157:H7 strain, led to identification of a putative fimbrial operon that promotes colonization of young calves (1 to 2 weeks old). The distribution of the gene encoding the major fimbrial subunit present in O-island 61 of EHEC O157:H7 in a characterized set of 78 diarrheagenic E. coli strains was determined, and this gene was found in 87.2% of the strains and is therefore not an EHEC-specific region. The cluster was amplified by long-range PCR and cloned into the inducible expression vector pBAD18. Induced expression in E. coli K-12 led to production of fimbriae, as demonstrated by transmission electron microscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The fimbriae were purified, and sera to the purified major subunit were raised and used to demonstrate expression from wild-type E. coli O157:H7 strains. Induced expression of the fimbriae, designated F9 fimbriae, was used to characterize binding to bovine epithelial cells, bovine gastrointestinal tissue explants, and extracellular matrix components. The fimbriae promoted increases in the levels of E. coli K-12 binding only to bovine epithelial cells. In contrast, induced expression of F9 fimbriae in E. coli O157:H7 significantly reduced adherence of the bacteria to bovine gastrointestinal explant tissue. This may have been due to physical hindrance of type III secretion-dependent attachment. The main F9 subunit gene was deleted in E. coli O157:H7, and the resulting mutant was compared with the wild-type strain for colonization in weaned cattle. While the shedding levels of the mutant were reduced, the animals were still colonized at the terminal rectum, indicating that the adhesin is not responsible for the rectal tropism observed but may contribute to colonization at other sites, as demonstrated previously with very young animals.

scholarly journals Identification and Characterization of a New Lipoprotein, NlpI, in Escherichia coli K-12

1999 ◽  
Vol 181 (14) ◽  
pp. 4318-4325 ◽  
Author(s):  
Masaru Ohara ◽  
Henry C. Wu ◽  
Krishnan Sankaran ◽  
Paul D. Rick
Keyword(s):  
Escherichia Coli ◽  
Direct Consequence ◽  
Insertion Mutant ◽  
Polynucleotide Phosphorylase ◽  
Wild Type ◽  
E Coli ◽  
K 12 ◽  
Identification And Characterization ◽  
Lines Of Evidence

ABSTRACT We report here the identification of a new lipoprotein, NlpI, inEscherichia coli K-12. The NlpI structural gene (nlpI) is located between the genes pnp(polynucleotide phosphorylase) and deaD (RNA helicase) at 71 min on the E. coli chromosome. The nlpI gene encodes a putative polypeptide of approximately 34 kDa, and multiple lines of evidence clearly demonstrate that NlpI is indeed a lipoprotein. An nlpI::cm mutation rendered growth of the cells osmotically sensitive, and incubation of the insertion mutant at an elevated temperature resulted in the formation of filaments. The altered phenotype of the mutant was a direct consequence of the mutation in nlpI, since it was complemented by the wild-type nlpI gene alone. Overexpression of the unaltered nlpI gene in wild-type cells resulted in the loss of the rod morphology and the formation of single prolate ellipsoids and pairs of prolate ellipsoids joined by partial constrictions. NlpI may be important for an as-yet-undefined step in the overall process of cell division.

scholarly journals HosA, a Member of the SlyA Family, Regulates Motility in Enteropathogenic Escherichia coli

2005 ◽  
Vol 73 (3) ◽  
pp. 1684-1694 ◽  
Author(s):  
Maria-José Ferrándiz ◽  
Keith Bishop ◽  
Paul Williams ◽  
Helen Withers
Keyword(s):  
Escherichia Coli ◽  
Transcriptional Regulators ◽  
Positive Control ◽  
Broth Culture ◽  
Wild Type ◽  
Mobility Shift ◽  
E Coli ◽  
Protein Levels ◽  
K 12 ◽  
Electrophoretic Mobility Shift Assays

ABSTRACT In enteropathogenic and enterohemorraghic Escherichia coli (EPEC and EHEC), two members of the SlyA family of transcriptional regulators have been identified as SlyA. Western blot analysis of the wild type and the corresponding hosA and slyA deletion mutants indicated that SlyA and HosA are distinct proteins whose expression is not interdependent. Of 27 different E. coli strains (EPEC, EHEC, enteroinvasive, enteroaggregative, uropathogenic, and commensal) examined, 14 were positive for both genes and proteins. To investigate hosA expression, a hosA::luxCDABE reporter gene fusion was constructed. hosA expression was significantly reduced in the hosA but not the slyA mutant and was influenced by temperature, salt, and pH. In contrast to SlyA, HosA did not activate the cryptic E. coli K-12 hemolysin ClyA. Mutation of hosA did not influence type III secretion, the regulation of the LEE1 and LEE4 operons, or the ability of E2348/69 to form attaching-and-effacing lesions on intestinal epithelial cells. HosA is, however, involved in the temperature-dependent positive control of motility on swim plates and regulates fliC expression and FliC protein levels. In electrophoretic mobility shift assays, purified HosA protein bound specifically to the fliC promoter, indicating that HosA directly modulates flagellin expression. While direct examination of flagellar structure and the motile behavior of individual hosA cells grown in broth culture at 30°C did not reveal any obvious differences, hosA mutants, unlike the wild type, clumped together, forming nonmotile aggregates which could account for the markedly reduced motility of the hosA mutant on swim plates at 30°C. We conclude that SlyA and HosA are independent transcriptional regulators that respond to different physicochemical cues to facilitate the environmental adaptation of E. coli.

scholarly journals The Transcriptional Antiterminator RfaH Represses Biofilm Formation in Escherichia coli

2006 ◽  
Vol 188 (4) ◽  
pp. 1316-1331 ◽  
Author(s):  
Christophe Beloin ◽  
Kai Michaelis ◽  
Karin Lindner ◽  
Paolo Landini ◽  
Jörg Hacker ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Biofilm Formation ◽  
Wild Type Strain ◽  
Wild Type ◽  
Strain Mg1655 ◽  
Upec Strain ◽  
E Coli ◽  
Initial Adhesion ◽  
State Production ◽  
K 12

ABSTRACT We investigated the influence of regulatory and pathogenicity island-associated factors (Hha, RpoS, LuxS, EvgA, RfaH, and tRNA5 Leu) on biofilm formation by uropathogenic Escherichia coli (UPEC) strain 536. Only inactivation of rfaH, which encodes a transcriptional antiterminator, resulted in increased initial adhesion and biofilm formation by E. coli 536. rfaH inactivation in nonpathogenic E. coli K-12 isolate MG1655 resulted in the same phenotype. Transcriptome analysis of wild-type strain 536 and an rfaH mutant of this strain revealed that deletion of rfaH correlated with increased expression of flu orthologs. flu encodes antigen 43 (Ag43), which mediates autoaggregation and biofilm formation. We confirmed that deletion of rfaH leads to increased levels of flu and flu-like transcripts in E. coli K-12 and UPEC. Supporting the hypothesis that RfaH represses biofilm formation through reduction of the Ag43 level, the increased-biofilm phenotype of E. coli MG1655rfaH was reversed upon inactivation of flu. Deletion of the two flu orthologs, however, did not modify the behavior of mutant 536rfaH. Our results demonstrate that the strong initial adhesion and biofilm formation capacities of strain MG1655rfaH are mediated by both increased steady-state production of Ag43 and likely increased Ag43 presentation due to null rfaH-dependent lipopolysaccharide depletion. Although the roles of rfaH in the biofilm phenotype are different in UPEC strain 536 and K-12 strain MG1655, this study shows that RfaH, in addition to affecting the expression of bacterial virulence factors, also negatively controls expression and surface presentation of Ag43 and possibly another Ag43-independent factor(s) that mediates cell-cell interactions and biofilm formation.

scholarly journals Virulence factors of Escherichia coli: an overview of animal and human infections with emphasis in bovine mastitis

2019 ◽  
Vol 40 (5) ◽  
pp. 2087
Author(s):  
Simony Trevizan Guerra ◽  
Carolina Lechinski de Paula ◽  
Carmen Alicia Daza Bolaños ◽  
Rodrigo Tavanelli Hernandes ◽  
Márcio Garcia Ribeiro
Keyword(s):  
Escherichia Coli ◽  
Virulence Factors ◽  
Bovine Mastitis ◽  
Clinical Mastitis ◽  
Clinical Severity ◽  
E Coli ◽  
Intestinal Infections ◽  
Wide Range ◽  
Environmental Agents ◽  
The Impact

Escherichia coli is a normal inhabitant of the enteric microflora of human and animal. Intestinal and extra-intestinal infections caused by E. coli in mammals are characterized by the presence of diversity of virulence factors. In addition it can be isolated from environment surrounding human and animal farms. E. coli is the main environmental pathogen causing clinical mastitis in dairy cattle. It causes a wide range of disease severity, from changes seen exclusively in milk to severe systemic signs. The severity of clinical mastitis has been conventionally classified into three levels: mild (grade 1), moderate (score 2), and severe (score 3). Recently, reports of cases of bovine mastitis caused by environmental agents have been on the rise, in particular in countries that have succeeded in controlling contagious microorganisms. Unlike enteric and certain extra-enteric conditions in domestic animals and humans, the impact of virulence factors on the occurrence of bovine mastitis due to E. coli, as well as the clinical severity of the cases, is not fully understood. In this regard, the present study reviewed the most relevant virulence factors of E. coli in human and animals, with emphasis in bovine mastitis.

KINETICS OF THREONINE DEAMINASE OF ESCHERICHIA COLI K-12 AND A STREPTOMYCIN-DEPENDENT MUTANT

1967 ◽  
Vol 45 (1) ◽  
pp. 1-10 ◽  
Author(s):  
I. D. Desai ◽  
W. J. Polglase
Keyword(s):  
Escherichia Coli ◽  
Selective Advantage ◽  
Kinetic Properties ◽  
Wild Type ◽  
Threonine Deaminase ◽  
E Coli ◽  
Type K ◽  
Hyperbolic Curve ◽  
K 12 ◽  
Kinetics Of

The relation between threonine deaminase activity and threonine concentration in sonic extracts of wild-type and streptomycin-dependent Escherichia coli K-12 was found to follow a hyperbolic curve. A similar relationship was obtained between enzyme activity and pyridoxal concentration. However, when serine was used as substrate, the activity–concentration curve was sigmoid, suggesting that serine may be a weaker effector of allosteric transition than threonine. The kinetic properties of the (derepressed) threonine deaminase of streptomycin-dependent E. coli K-12 were found to be similar to those of the enzyme of the wild-type K-12.It is postulated that derepression of threonine deaminase in streptomycin-dependent E. coli K-12 provides a selective advantage which permits exponential growth of this mutant in the presence of L-valine, which is an excretory product of streptomycin-dependent microorganisms.

scholarly journals Positive control of sulphate reduction in Escherichia coli. The nature of the pleiotropic cysteineless mutants of E. coli K 12

1968 ◽  
Vol 110 (3) ◽  
pp. 597-602 ◽  
Author(s):  
M. C. Jones-Mortimer
Keyword(s):  
Escherichia Coli ◽  
Mutant Allele ◽  
Positive Control ◽  
Wild Type Allele ◽  
Wild Type ◽  
E Coli ◽  
Type Allele ◽  
K 12 ◽  
Sulphite Reductase

1. The function of the wild-type alleles of the pleiotropic mutants cysB and cysE of Escherichia coli was investigated. 2. The wild-type allele cysB+ is dominant to the mutant allele cysB in stable and transient heterozygotes. 3. The wild-type allele cysE+ is dominant to the mutant allele cysE, as predicted. 4. Sulphur-starved cultures of cysB or cysE strains contain less than 0·2nmole of free cysteine/mg. dry wt. 5. Complementation in vitro is not observed between extracts of cysB mutants and mutants lacking sulphite reductase only. 6. A scheme, involving positive control of the enzymes of sulphate activation and reduction, is suggested to account for the control of cysteine biosynthesis.

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