scholarly journals Multiple functions of l0036 in the regulation of the pathogenicity island of enterohaemorrhagic Escherichia coli O157:H7

2005 ◽  
Vol 393 (2) ◽  
pp. 591-599 ◽  
Author(s):  
Nien-Pei Tsai ◽  
Yi-Chih Wu ◽  
Jenn-Wei Chen ◽  
Chih-Feng Wu ◽  
Chi-Meng Tzeng ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Current Knowledge ◽  
Regulatory Gene ◽  
Pathogenicity Island ◽  
Negative Regulator ◽  
Multiple Point ◽  
Global Regulator ◽  
Multiple Functions ◽  
E Coli ◽  
Enterohaemorrhagic Escherichia Coli

Diarrhoeagenic enterohaemorrhagic Escherichia coli and enteropathogenic E. coli attach to human intestinal epithelium and efface brush-border microvilli, forming an A/E (attaching and effacing) lesion. These human pathogens are phenotypically similar to the mouse pathogen Citrobacter rodentium. Genetically, they all have a homologous set of virulent genes involved in the A/E lesion, and these genes are organized on a LEE (locus of enterocyte effacement), a pathogenicity island. This island comprises 41 specific open reading frames, of which most are organized at five operons, LEE1, LEE2, LEE3, LEE4 and tir (LEE5). The expression of the LEE genes is regulated in a complicated manner, and current knowledge is that there are at least two positive regulators, Ler (LEE-encoded regulator) and GrlA (global regulator of LEE activator), and one negative regulator, called GrlR (global regulator of LEE repressor). In enterohaemorrhagic E. coli, GrlA is encoded by l0043, whereas GrlR is encoded by l0044. Here we report a fourth regulatory gene located in LEE3, namely l0036. Its expression is tightly controlled. When overexpressed, this factor, named Mpc (multiple point controller), interacts with Ler and suppresses the expression of the LEE proteins. When the translation is not initiated or terminated before maturation, the type III secretion of effectors is completely abolished. Therefore, together with the fact that several cis elements reside in the region that l0036 spans, l0036 appeared to have multiple functions in the regulation of LEE expression.

scholarly journals afa-8 Gene Cluster Is Carried by a Pathogenicity Island Inserted into the tRNAPhe of Human and Bovine Pathogenic Escherichia coli Isolates

2001 ◽  
Vol 69 (2) ◽  
pp. 937-948 ◽  
Author(s):  
Lila Lalioui ◽  
Chantal Le Bouguénec
Keyword(s):  
Escherichia Coli ◽  
Direct Repeat ◽  
Pathogenicity Island ◽  
Genomic Region ◽  
Open Reading Frames ◽  
Blood Isolate ◽  
Distinctive Features ◽  
E Coli ◽  
Pathogenic Escherichia Coli ◽  
K 12

ABSTRACT We recently described a new afimbrial adhesin, AfaE-VIII, produced by animal strains associated with diarrhea and septicemia and by human isolates associated with extraintestinal infections. Here, we report that the afa-8 operon, encoding AfaE-VIII adhesin, from the human blood isolate Escherichia coli AL862 is carried by a 61-kb genomic region with characteristics typical of a pathogenicity island (PAI), including a size larger than 10 kb, the presence of an integrase-encoding gene, the insertion into a tRNA locus (pheR), and the presence of a small direct repeat at each extremity. Moreover, the G+C content of the afa-8 operon (46.4%) is lower than that of the E. coli K-12/MG1655 chromosome (50.8%). Within this PAI, designated PAI IAL862, we identified open reading frames able to code for products similar to proteins involved in sugar utilization. Four probes spanning these sequences hybridized with 74.3% of pathogenicafa-8-positive E. coli strains isolated from humans and animals, 25% of human pathogenic afa-8-negativeE. coli strains, and only 8% of fecal strains (P = 0.05), indicating that these sequences are strongly associated with the afa-8 operon and that this genetic association may define a PAI widely distributed among human and animal afa-8-positive strains. One of the distinctive features of this study is that E. coli AL862 also carries another afa-8-containing PAI (PAI IIAL862), which appeared to be similar in size and genetic organization to PAI IAL862 and was inserted into the pheV gene. We investigated the insertion sites of afa-8-containing PAI in human and bovine pathogenic E. coli strains and found that this PAI preferentially inserted into the pheV gene.

scholarly journals Increased Mutation Frequency in Redox-Impaired Escherichia coli Due to RelA- and RpoS-Mediated Repression of DNA Repair

2010 ◽  
Vol 76 (16) ◽  
pp. 5463-5470 ◽  
Author(s):  
Amarjeet Singh ◽  
Anis Karimpour-Fard ◽  
Ryan T. Gill
Keyword(s):  
Escherichia Coli ◽  
Dna Repair ◽  
Mutation Frequency ◽  
Spontaneous Mutation ◽  
Regulatory Gene ◽  
Stringent Response ◽  
Anaerobic Growth ◽  
E Coli ◽  
Direct Measurements ◽  
Order Of Magnitude

ABSTRACT Balancing of reducing equivalents is a fundamental issue in bacterial metabolism and metabolic engineering. Mutations in the key metabolic genes ldhA and pflB of Escherichia coli are known to stall anaerobic growth and fermentation due to a buildup of intracellular NADH. We observed that the rate of spontaneous mutation in E. coli BW25113 (ΔldhA ΔpflB) was an order of magnitude higher than that in wild-type (WT) E. coli BW25113. We hypothesized that the increased mutation frequency was due to an increased NADH/NAD+ ratio in this strain. Using several redox-impaired strains of E. coli and different redox conditions, we confirmed a significant correlation (P < 0.01) between intracellular-NADH/NAD+ ratio and mutation frequency. To identify the genetic basis for this relationship, whole-genome transcriptional profiles were compared between BW25113 WT and BW25113 (ΔldhA ΔpflB). This analysis revealed that the genes involved in DNA repair were expressed at significantly lower levels in BW25113 (ΔldhA ΔpflB). Direct measurements of the extent of DNA repair in BW25113 (ΔldhA ΔpflB) subjected to UV exposure confirmed that DNA repair was inhibited. To identify a direct link between DNA repair and intracellular-redox ratio, the stringent-response-regulatory gene relA and the global-stress-response-regulatory gene rpoS were deleted. In both cases, the mutation frequencies were restored to BW25113 WT levels.

scholarly journals Natural Genetic Transformation of Clinical Isolates of Escherichia coli in Urine and Water

2002 ◽  
Vol 68 (1) ◽  
pp. 440-443 ◽  
Author(s):  
Markus Woegerbauer ◽  
Bernard Jenni ◽  
Florian Thalhammer ◽  
Wolfgang Graninger ◽  
Heinz Burgmann
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Current Knowledge ◽  
Antibiotic Resistance Genes ◽  
Aquatic Environments ◽  
Wild Type ◽  
E Coli ◽  
Naturally Occurring ◽  
Natural Genetic Transformation ◽  
Type Strains

ABSTRACT Transfer of plasmid-borne antibiotic resistance genes in Escherichia coli wild-type strains is possible by transformation under naturally occurring conditions in oligotrophic, aquatic environments containing physiologic concentrations of calcium. In contrast, transformation is suppressed in nitrogen-rich body fluids like urine, a common habitat of uropathogenic strains. Current knowledge indicates that transformation of these E. coli wild-type strains is of no relevance for the acquisition of resistance in this clinically important environment.

scholarly journals Quorum-Sensing Escherichia coli Regulator A: a Regulator of the LysR Family Involved in the Regulation of the Locus of Enterocyte Effacement Pathogenicity Island in Enterohemorrhagic E. coli

2002 ◽  
Vol 70 (6) ◽  
pp. 3085-3093 ◽  
Author(s):  
Vanessa Sperandio ◽  
Caiyi C. Li ◽  
James B. Kaper
Keyword(s):  
Escherichia Coli ◽  
Quorum Sensing ◽  
Type Iii Secretion ◽  
Pathogenicity Island ◽  
The Other ◽  
E Coli ◽  
Type Iii ◽  
Enterocyte Effacement ◽  
K 12 ◽  
Lysr Family

ABSTRACT The locus of enterocyte effacement (LEE) is a chromosomal pathogenicity island that encodes the proteins involved in the formation of the attaching and effacing lesions by enterohemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC). The LEE comprises 41 open reading frames organized in five major operons, LEE1, LEE2, LEE3, tir (LEE5), and LEE4, which encode a type III secretion system, the intimin adhesin, the translocated intimin receptor (Tir), and other effector proteins. The first gene of LEE1 encodes the Ler regulator, which activates all the other genes within the LEE. We previously reported that the LEE genes were activated by quorum sensing through Ler (V. Sperandio, J. L. Mellies, W. Nguyen, S. Shin, and J. B. Kaper, Proc. Natl. Acad. Sci. USA 96:15196-15201, 1999). In this study we report that a putative regulator in the E. coli genome is itself activated by quorum sensing. This regulator is encoded by open reading frame b3243; belongs to the LysR family of regulators; is present in EHEC, EPEC, and E. coli K-12; and shares homology with the AphB and PtxR regulators of Vibrio cholerae and Pseudomonas aeruginosa, respectively. We confirmed the activation of b3243 by quorum sensing by using transcriptional fusions and renamed this regulator quorum-sensing E. coli regulator A (QseA). We observed that QseA activated transcription of ler and therefore of the other LEE genes. An EHEC qseA mutant had a striking reduction of type III secretion activity, which was complemented when qseA was provided in trans. Similar results were also observed with a qseA mutant of EPEC. The QseA regulator is part of the regulatory cascade that regulates EHEC and EPEC virulence genes by quorum sensing.

scholarly journals Impacts of Hematite Nanoparticle Exposure on Biomechanical, Adhesive, and Surface Electrical Properties of Escherichia coli Cells

2012 ◽  
Vol 78 (11) ◽  
pp. 3905-3915 ◽  
Author(s):  
Wen Zhang ◽  
Joseph Hughes ◽  
Yongsheng Chen
Keyword(s):  
Escherichia Coli ◽  
Electrical Properties ◽  
Current Knowledge ◽  
Statistical Significance ◽  
Spring Constant ◽  
Bacterial Cells ◽  
Kelvin Probe ◽  
Content Type ◽  
Force Microscopy ◽  
E Coli

ABSTRACTDespite a wealth of studies examining the toxicity of engineered nanomaterials, current knowledge on their cytotoxic mechanisms (particularly from a physical perspective) remains limited. In this work, we imaged and quantitatively characterized the biomechanical (hardness and elasticity), adhesive, and surface electrical properties ofEscherichia colicells with and without exposure to hematite nanoparticles (NPs) in an effort to advance our understanding of the cytotoxic impacts of nanomaterials. Both scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed thatE. colicells had noticeable deformation with hematite treatment for 45 min with a statistical significance. The hematite-treated cells became significantly harder or stiffer than untreated ones, as evidenced by indentation and spring constant measurements. The average indentation of the hematite-treatedE. colicells was 120 nm, which is significantly lower (P< 0.01) than that of the untreated cells (approximately 400 nm). The spring constant of hematite-treatedE. colicells (0.28 ± 0.11 nN/nm) was about 20 times higher than that of untreated ones (0.01 ± 0.01 nN/nm). The zeta potential ofE. colicells, measured by dynamic light scattering (DLS), was shown to shift from −4 ± 2 mV to −27 ± 8 mV with progressive surface adsorption of hematite NPs, a finding which is consistent with the local surface potential measured by Kelvin probe force microscopy (KPFM). Overall, the reported findings quantitatively revealed the adverse impacts of nanomaterial exposure on physical properties of bacterial cells and should provide insight into the toxicity mechanisms of nanomaterials.

scholarly journals Novel Translation Initiation Regulation Mechanism in Escherichia coli ptrB Mediated by a 5′-Terminal AUG

2017 ◽  
Vol 199 (14) ◽  
Author(s):  
Heather J. Beck ◽  
Gary R. Janssen
Keyword(s):  
Escherichia Coli ◽  
Translation Initiation ◽  
Translational Regulation ◽  
Current Knowledge ◽  
Upstream Open Reading Frame ◽  
Model Organisms ◽  
Regulation Mechanism ◽  
Rna Regulation ◽  
Content Type ◽  
E Coli

ABSTRACT Alternative translation initiation mechanisms, distinct from the Shine-Dalgarno (SD) sequence-dependent mechanism, are more prevalent in bacteria than once anticipated. Translation of Escherichia coli ptrB instead requires an AUG triplet at the 5′ terminus of its mRNA. The 5′-terminal AUG (5′-uAUG) acts as a ribosomal recognition signal to attract ribosomes to the ptrB mRNA rather than functioning as an initiation codon to support translation of an upstream open reading frame. ptrB expression exhibits a stronger dependence on the 5′-uAUG than the predicted SD sequence; however, strengthening the predicted ptrB SD sequence relieves the necessity for the 5′-uAUG. Additional sequences within the ptrB 5′ untranslated region (5′-UTR) work cumulatively with the 5′-uAUG to control expression of the downstream ptrB coding sequence (CDS), thereby compensating for the weak SD sequence. Replacement of 5′-UTRs from other mRNAs with the ptrB 5′-UTR sequence showed a similar dependence on the 5′-uAUG for CDS expression, suggesting that the regulatory features contained within the ptrB 5′-UTR are sufficient to control the expression of other E. coli CDSs. Demonstration that the 5′-uAUG present on the ptrB leader mRNA is involved in ribosome binding and expression of the downstream ptrB CDS revealed a novel form of translational regulation. Due to the abundance of AUG triplets at the 5′ termini of E. coli mRNAs and the ability of ptrB 5′-UTR regulation to function independently of gene context, the regulatory effects of 5′-uAUGs on downstream CDSs may be widespread throughout the E. coli genome. IMPORTANCE As the field of synthetic biology continues to grow, a complete understanding of basic biological principles will be necessary. The increasing complexity of the synthetic systems highlights the gaps in our current knowledge of RNA regulation. This study demonstrates that there are novel ways to regulate canonical Shine-Dalgarno-led mRNAs in Escherichia coli, illustrating that our understanding of the fundamental processes of translation and RNA regulation is still incomplete. Even for E. coli, one of the most-studied model organisms, genes with translation initiation mechanisms that do not fit the canonical Shine-Dalgarno sequence paradigm are being revealed. Uncovering diverse mechanisms that control translational expression will allow synthetic biologists to finely tune protein production of desired gene products.

scholarly journals Regulation of virulence by butyrate sensing in enterohaemorrhagic Escherichia coli

Microbiology ◽  
2009 ◽  
Vol 155 (2) ◽  
pp. 521-530 ◽  
Author(s):  
Noriko Nakanishi ◽  
Kosuke Tashiro ◽  
Satoru Kuhara ◽  
Tetsuya Hayashi ◽  
Nakaba Sugimoto ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Virulence Genes ◽  
Regulatory Protein ◽  
Short Chain Fatty Acids ◽  
Global Regulator ◽  
Cell Adherence ◽  
High Concentration ◽  
Enterohaemorrhagic Escherichia Coli ◽  
Low Concentrations ◽  
Colonic Health

Enterohaemorrhagic Escherichia coli (EHEC) colonizes and proliferates at the mucosal surface, inducing severe diarrhoea. Short-chain fatty acids (SCFAs) are abundant in the intestine owing to the metabolic activity of microflora, and are important for colonic health. We found that, although a high concentration of SCFAs inhibited the growth of EHEC, at low concentrations, the SCFAs markedly enhanced the expression of the virulence genes required for cell adherence and the induction of attaching and effacing (A/E) lesions. Of the SCFAs tested, butyrate markedly enhanced the expression of these virulence-associated genes, even at the low concentration of 1.25 mM, but acetate and propionate showed only a small effect at concentrations higher than 40 mM. Butyrate enhanced the promoter activity of the LEE1 operon, which encodes a global regulator of the LEE genes, Ler. This enhancement was dependent on a regulator, PchA. Butyrate sensing was completely abrogated by the deletion of lrp, the gene for the leucine-responsive regulatory protein, Lrp. Expression of a constitutively active mutant of Lrp enhanced the expression of the LEE genes in the absence of butyrate, and a response-defective Lrp derivative reduced the response to butyrate. Thus, upon entering the distal ileum, EHEC may respond to the higher butyrate level via Lrp by increasing its virulence expression, leading to efficient colonization of the target niche.

scholarly journals Employment of a Promoter-Swapping Technique Shows that PhoU Modulates the Activity of the PstSCAB2 ABC Transporter in Escherichia coli

2008 ◽  
Vol 75 (3) ◽  
pp. 573-582 ◽  
Author(s):  
Christopher D. Rice ◽  
Jacob E. Pollard ◽  
Zachery T. Lewis ◽  
William R. McCleary
Keyword(s):  
Escherichia Coli ◽  
Regulatory System ◽  
Negative Regulator ◽  
Growth Defect ◽  
Pho Regulon ◽  
E Coli ◽  
Regulatory Module ◽  
Two Component ◽  
Severe Growth Defect ◽  
Promoter Swapping

ABSTRACT Expression of the Pho regulon in Escherichia coli is induced in response to low levels of environmental phosphate (Pi). Under these conditions, the high-affinity PstSCAB2 protein (i.e., with two PstB proteins) is the primary Pi transporter. Expression from the pstSCAB-phoU operon is regulated by the PhoB/PhoR two-component regulatory system. PhoU is a negative regulator of the Pho regulon; however, the mechanism by which PhoU accomplishes this is currently unknown. Genetic studies of phoU have proven to be difficult because deletion of the phoU gene leads to a severe growth defect and creates strong selection for compensatory mutations resulting in confounding data. To overcome the instability of phoU deletions, we employed a promoter-swapping technique that places expression of the phoBR two-component system under control of the Ptac promoter and the lacO ID regulatory module. This technique may be generally applicable for controlling expression of other chromosomal genes in E. coli. Here we utilized PphoB ::Ptac and PpstS ::Ptac strains to characterize phenotypes resulting from various ΔphoU mutations. Our results indicate that PhoU controls the activity of the PstSCAB2 transporter, as well as its abundance within the cell. In addition, we used the PphoB ::Ptac ΔphoU strain as a platform to begin characterizing new phoU mutations in plasmids.

scholarly journals Enhanced Expression of the Multidrug Efflux Pumps AcrAB and AcrEF Associated with Insertion Element Transposition in Escherichia coli Mutants Selected with a Fluoroquinolone

2001 ◽  
Vol 45 (5) ◽  
pp. 1467-1472 ◽  
Author(s):  
A. S. Jellen-Ritter ◽  
W. V. Kern
Keyword(s):  
Escherichia Coli ◽  
In Vitro Selection ◽  
Regulatory Gene ◽  
Fluoroquinolone Resistance ◽  
Upstream Region ◽  
Single Mutation ◽  
Multidrug Efflux ◽  
E Coli ◽  
Enhanced Expression ◽  
K 12

ABSTRACT The development of fluoroquinolone resistance in Escherichia coli may be associated with mutations in regulatory gene loci such as marRAB that lead to increased multidrug efflux, presumably through activation of expression of the AcrAB multidrug efflux pump. We found that multidrug-resistant (MDR) phenotypes with enhanced efflux can also be selected by fluoroquinolones frommarRAB- or acrAB-inactivated E. coli K-12 strains having a single mutation in the quinolone-resistance-determining region of gyrA. Mutant 3-AG100MKX, obtained from a mar knockout strain after two selection steps, showed enhanced expression of acrB in a reverse transcriptase PCR associated with insertion of IS186 into the AcrAB repressor gene acrR. In vitro selection experiments with acrAB knockout strains yielded MDR mutants after a single step. Enhanced efflux in these mutants was due to increased expression of acrEF and associated with insertion of IS2 into the upstream region ofacrEF, presumably creating a hybrid promoter. These observations confirm the importance of efflux-associated nontarget gene mutations and indicate that transposition of genetic elements may have a role in the development of fluoroquinolone resistance in E. coli.

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