A Genomic Islet Mediates Flagellar Phase Variation in Escherichia coli Strains Carrying the Flagellin-Specifying Locus flk

ABSTRACT The occurrence of unilateral flagellar phase variation was previously demonstrated in Escherichia coli strains carrying the non-fliC flagellin-specifying locus flk. In this study, we investigated the mechanism involved in this process. By using sequencing and sequence analysis, the flk region between the chromosomal genes yhaC and rnpB was characterized in all described flk-positive E. coli strains, including the H35 strain identified in this study (the other strains used are H3, H36, H47, and H53 strains), and this region was found to contain a putative integrase gene and flanking direct repeats in addition to the flk flagellin-specifying gene flkA and a fliC repressor gene, flkB, indicating that there is a typical genomic islet (GI), which was designated the flk GI. The horizontal transfer potential of the flk GI was indicated by detection of the excised extrachromosomal circular form of the flk GI. By generating fliC-expressing variants of H3 and H47 strains, unilateral flagellar phase variation in flk-positive strains was shown to be mediated by excision of the flk GI. The function of the proposed integrase gene was confirmed by deletion and a complementation test. The potential integration sites of the flk GI were identified. A general model for flagellar phase variation in flk-positive E. coli strains can be expressed as fliC off + flkA on → fliC on + flkA none. This is the first time that a molecular mechanism for flagellar phase variation has been reported for E. coli.

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Regulation of P-Fimbrial Phase Variation Frequencies in Escherichia coli CFT073

Infection and Immunity ◽

10.1128/iai.01989-06 ◽

2007 ◽

Vol 75 (7) ◽

pp. 3325-3334 ◽

Cited By ~ 30

Author(s):

Nicola Holden ◽

Makrina Totsika ◽

Lynn Dixon ◽

Kirsteen Catherwood ◽

David L. Gally

Keyword(s):

Escherichia Coli ◽

Phase Transition ◽

Regulatory Region ◽

Phase Variation ◽

Culture Conditions ◽

Host Tissue ◽

Clinical Isolates ◽

E Coli ◽

K 12 ◽

First Time

ABSTRACT Adherence of uropathogenic Escherichia coli to host tissue is required for infection and is mediated by fimbriae, such as pyelonephritis-associated pili (Pap). Expression of P fimbriae is regulated by phase variation, and to date, phase transition frequencies have been measured only for pap regulatory region constructs integrated into the E. coli K-12 chromosome. The aim of this work was to measure P phase transition frequencies in clinical isolates for the first time, including frequencies for the sequenced strain E. coli CFT073. P fimbriation and associated phase transition frequencies were measured for two E. coli clinical isolates and compared with levels for homologous pap constructs in E. coli K-12. Fimbriation and off-to-on transition frequencies were always higher in the clinical isolate. It was concluded that the regulatory inputs controlling papI expression are likely to be different in E. coli CFT073 and E. coli K-12 as (i) phase variation could be stimulated in E. coli K-12 by induction of papI and (ii) the level of expression of a papI::gfp + fusion was higher in E. coli CFT073 than in E. coli K-12. Furthermore, phase transition frequencies for the two E. coli CFT073 pap clusters were shown to be different depending on the culture conditions, indicating that there is a hierarchy of expression depending on signal inputs.

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Induction and control of the autolytic system of Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.152.1.26-34.1982 ◽

1982 ◽

Vol 152 (1) ◽

pp. 26-34

Author(s):

M Leduc ◽

R Kasra ◽

J van Heijenoort

Keyword(s):

Escherichia Coli ◽

Fatty Acid ◽

Acid Synthesis ◽

Induction Method ◽

E Coli ◽

Escherichia Coli Cells ◽

Carbonyl Cyanide ◽

And Control ◽

First Time ◽

Induced Autolysis

Various methods of inducing autolysis of Escherichia coli cells were investigated, some being described here for the first time. For the autolysis of growing cells only induction methods interfering with the biosynthesis of peptidoglycan were taken into consideration, whereas with harvested cells autolysis was induced by rapid osmotic or EDTA shock treatments. The highest rates of autolysis were observed after induction by moenomycin, EDTA, or cephaloridine. The different autolyses examined shared certain common properties. In particular, regardless of the induction method used, more or less extensive peptidoglycan degradation was observed, and 10(-2) M Mg2+ efficiently inhibited the autolytic process. However, for other properties a distinction was made between methods used for growing cells and those used for harvested cells. Autolysis of growing cells required RNA, protein, and fatty acid synthesis. No such requirements were observed with shock-induced autolysis performed with harvested cells. Thus, the effects of Mg2+, rifampicin, chloramphenicol, and cerulenin clearly suggest that distinct factors are involved in the control of the autolytic system of E. Coli. Uncoupling agents such as sodium azide, 2,4-dinitrophenol, and carbonyl-cyanide-m-chlorophenyl hydrazone used at their usual inhibiting concentration had no effect on the cephaloridine or shock-induced autolysis.

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Redesigning Escherichia coli Metabolism for Anaerobic Production of Isobutanol

Applied and Environmental Microbiology ◽

10.1128/aem.00382-11 ◽

2011 ◽

Vol 77 (14) ◽

pp. 4894-4904 ◽

Cited By ~ 79

Author(s):

Cong T. Trinh ◽

Johnny Li ◽

Harvey W. Blanch ◽

Douglas S. Clark

Keyword(s):

Escherichia Coli ◽

Anaerobic Growth ◽

Mode Analysis ◽

Glycolytic Flux ◽

Strictly Anaerobic ◽

Anaerobic Conditions ◽

Content Type ◽

E Coli ◽

Model Predictions ◽

Chromosomal Genes

ABSTRACTFermentation enables the production of reduced metabolites, such as the biofuels ethanol and butanol, from fermentable sugars. This work demonstrates a general approach for designing and constructing a production host that uses a heterologous pathway as an obligately fermentative pathway to produce reduced metabolites, specifically, the biofuel isobutanol. Elementary mode analysis was applied to design anEscherichia colistrain optimized for isobutanol production under strictly anaerobic conditions. The central metabolism ofE. coliwas decomposed into 38,219 functional, unique, and elementary modes (EMs). The model predictions revealed that during anaerobic growthE. colicannot produce isobutanol as the sole fermentative product. By deleting 7 chromosomal genes, the total 38,219 EMs were constrained to 12 EMs, 6 of which can produce high yields of isobutanol in a range from 0.29 to 0.41 g isobutanol/g glucose under anaerobic conditions. The remaining 6 EMs rely primarily on the pyruvate dehydrogenase enzyme complex (PDHC) and are typically inhibited under anaerobic conditions. The redesignedE. colistrain was constrained to employ the anaerobic isobutanol pathways through deletion of 7 chromosomal genes, addition of 2 heterologous genes, and overexpression of 5 genes. Here we present the design, construction, and characterization of an isobutanol-producingE. colistrain to illustrate the approach. The model predictions are evaluated in relation to experimental data and strategies proposed to improve anaerobic isobutanol production. We also show that the endogenous alcohol/aldehyde dehydrogenase AdhE is the key enzyme responsible for the production of isobutanol and ethanol under anaerobic conditions. The glycolytic flux can be controlled to regulate the ratio of isobutanol to ethanol production.

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A New 3-Prenyl-2-flavene and Other Extractives from Baphia massaiensis and Their Antimicrobial Activities

Natural Product Communications ◽

10.1177/1934578x1801300414 ◽

2018 ◽

Vol 13 (4) ◽

pp. 1934578X1801300 ◽

Cited By ~ 1

Author(s):

Ngonye Keroletswe ◽

Runner R. T. Majinda ◽

Ishmael B. Masesane

Keyword(s):

Escherichia Coli ◽

2D Nmr ◽

Antimicrobial Activities ◽

Spectroscopic Techniques ◽

Good Activity ◽

Gram Negative ◽

E Coli ◽

Chromatographic Techniques ◽

Inhibition Zones ◽

First Time

One new 3-prenyl-2-flavene, named baphiflavene A, 1, and eleven known compounds, 2-12, were isolated and reported for the first time from Baphia massaiensis using several chromatographic techniques. Their structures were elucidated using different spectroscopic techniques; 1D and 2D-NMR, HRMS, GC-MS, UV/Vis, FTIR and by comparison with literature data. The isolates were tested against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli and Candida albicans to establish their preliminary antimicrobial activities. The results revealed that compound 1 had moderate activities against both Gram positive ( B. subtilis and S. aureus) and Gram negative ( E. coli and P. aeruginosa) bacteria, and good activity against C. albicans with inhibition zones of 10–23 mm (compared to 19 mm for chloramphenicol and miconazole standards). To the best of our knowledge, this is the first phytochemical work reported on Baphia massaiensis.

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Spread of NDM-5 and OXA-181 Carbapenemase-Producing Escherichia coli in Chad

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00646-19 ◽

2019 ◽

Vol 63 (11) ◽

Cited By ~ 2

Author(s):

Oumar Ouchar Mahamat ◽

Manon Lounnas ◽

Mallorie Hide ◽

Abelsalam Tidjani ◽

Julio Benavides ◽

...

Keyword(s):

Escherichia Coli ◽

Healthy Volunteers ◽

Resistance Genes ◽

Sequence Type ◽

Hospitalized Patients ◽

Content Type ◽

E Coli ◽

First Time

ABSTRACT We detected for the first time blaNDM-5 and blaOXA-181 in Escherichia coli isolates from hospitalized patients and healthy volunteers in Chad. These resistance genes were located on IncX3 and IncF plasmids. Despite the large diversity of E. coli clones, the identified resistant intestinal isolates belonged mainly to the same sequence type.

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The Transcriptional Factors MurR and Catabolite Activator Protein Regulate N-Acetylmuramic Acid Catabolism in Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.00642-08 ◽

2008 ◽

Vol 190 (20) ◽

pp. 6598-6608 ◽

Cited By ~ 26

Author(s):

Tina Jaeger ◽

Christoph Mayer

Keyword(s):

Escherichia Coli ◽

Cell Wall ◽

Sole Source ◽

Lag Phase ◽

Face To Face ◽

E Coli ◽

Catabolite Activator Protein ◽

Activator Protein ◽

High Level ◽

First Time

ABSTRACT The MurNAc etherase MurQ of Escherichia coli is essential for the catabolism of the bacterial cell wall sugar N-acetylmuramic acid (MurNAc) obtained either from the environment or from the endogenous cell wall (i.e., recycling). High-level expression of murQ is required for growth on MurNAc as the sole source of carbon and energy, whereas constitutive low-level expression of murQ is sufficient for the recycling of peptidoglycan fragments continuously released from the cell wall during growth of the bacteria. Here we characterize for the first time the expression of murQ and its regulation by MurR, a member of the poorly characterized RpiR/AlsR family of transcriptional regulators. Deleting murR abolished the extensive lag phase observed for E. coli grown on MurNAc and enhanced murQ transcription some 20-fold. MurR forms a stable multimer (most likely a tetramer) and binds to two adjacent inverted repeats within an operator region. In this way MurR represses transcription from the murQ promoter and also interferes with its own transcription. MurNAc-6-phosphate, the substrate of MurQ, was identified as a specific inducer that weakens binding of MurR to the operator. Moreover, murQ transcription depends on the activation by cyclic AMP (cAMP)-catabolite activator protein (CAP) bound to a class I site upstream of the murQ promoter. murR and murQ are divergently orientated and expressed from nonoverlapping face-to-face (convergent) promoters, yielding transcripts that are complementary at their 5′ ends. As a consequence of this unusual promoter arrangement, cAMP-CAP also affects murR transcription, presumably by acting as a roadblock for RNA polymerase.

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Characteristics of Emerging Human-Pathogenic Escherichia coli O26:H11 Strains Isolated in France between 2010 and 2013 and Carrying thestx2dGene Only

Journal of Clinical Microbiology ◽

10.1128/jcm.02290-14 ◽

2014 ◽

Vol 53 (2) ◽

pp. 486-492 ◽

Cited By ~ 35

Author(s):

Sabine Delannoy ◽

Patricia Mariani-Kurkdjian ◽

Stephane Bonacorsi ◽

Sandrine Liguori ◽

Patrick Fach

Keyword(s):

Escherichia Coli ◽

Virulence Gene ◽

Gene Profiling ◽

Content Type ◽

E Coli ◽

Negative Results ◽

Pathogenic Escherichia Coli ◽

Short Palindromic Repeat ◽

Uremic Syndrome ◽

First Time

Strains ofEscherichia coliO26:H11 that were positive forstx2alone (n= 23), which were not epidemiologically related or part of an outbreak, were isolated from pediatric patients in France between 2010 and 2013. We were interested in comparing these strains with the new highly virulentstx2a-positiveE. coliO26 clone sequence type 29 (ST29) that has emerged recently in Europe, and we tested them by multilocus sequence typing (MLST),stx2subtyping, clustered regularly interspaced short palindromic repeat (CRISPR) sequencing, and plasmid (ehxA,katP,espP, andetpD) and chromosomal (Z2098,espK, andespV) virulence gene profiling. We showed that 16 of the 23 strains appeared to correspond to this new clone, but the characteristics of 12 strains differed significantly from the previously described characteristics, with negative results for both plasmid and chromosomal genetic markers. These 12 strains exhibited a ST29 genotype and related CRISPR arrays (CRISPR2a alleles 67 or 71), suggesting that they evolved in a common environment. This finding was corroborated by the presence ofstx2din 7 of the 12 ST29 strains. This is the first time thatE. coliO26:H11 carryingstx2dhas been isolated from humans. This is additional evidence of the continuing evolution of virulent Shiga toxin-producingE. coli(STEC) O26 strains. A new O26:H11 CRISPR PCR assay, SP_O26_E, has been developed for detection of these 12 particular ST29 strains ofE. coliO26:H11. This test is useful to better characterize thestx2-positive O26:H11 clinical isolates, which are associated with severe clinical outcomes such as bloody diarrhea and hemolytic uremic syndrome.

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Cloning and Heterologous Expression of Plantaricin ZJ5, a Novel Bacteriocin from Lactobacillus plantarum ZJ5, in Escherichia coli

Natural Product Communications ◽

10.1177/1934578x1801301231 ◽

2018 ◽

Vol 13 (12) ◽

pp. 1934578X1801301

Author(s):

Dafeng Song ◽

Ping Li ◽

Qing Gu

Keyword(s):

Escherichia Coli ◽

Fusion Protein ◽

Lactobacillus Plantarum ◽

Micrococcus Luteus ◽

Biologically Active ◽

Biological Method ◽

Lac Operon ◽

E Coli ◽

First Time ◽

Soluble Material

A novel bacteriocin, plantaricin ZJ5 (PZJ5) was yielded from Lactobacillus plantarum ZJ5, cloned, and produced in Escherichia coli BL21 (DE3) pLys. The PZJ5 structural gene was fused with a Trx tag, and cloned into the pET32a plasmid under the control of the inducible lac operon. Induction was performed with isopropyl-β-D-thiogalactopyranoside (IPTG), with subsequent overexpression of the fusion protein, followed by purification to homogeneity via His affinity chromatography. Recombinant E. coli produced greater quantities of PZJ5 than L. plantarum ZJ5, and PZJ5 in E. coli was expressed in the form of soluble material. Biologically active PZJ5 was recovered by cleaving the purified fusion protein using enterokinase. The released PZJ5 demonstrated antibacterial activity against Micrococcus luteus. In this study, an inexpensive biological method using a Trx fusion system was presented, and for the first time, bacteriocin PZJ5 was expressed and purified in E. coli.

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Resistance Profiling and Molecular Characterization of Extended-Spectrum/Plasmid-Mediated AmpC β-Lactamase-Producing Escherichia coli Isolated from Healthy Broiler Chickens in South Korea

Microorganisms ◽

10.3390/microorganisms8091434 ◽

2020 ◽

Vol 8 (9) ◽

pp. 1434 ◽

Cited By ~ 1

Author(s):

Hyun-Ju Song ◽

Dong Chan Moon ◽

Abraham Fikru Mechesso ◽

Hee Young Kang ◽

Mi Hyun Kim ◽

...

Keyword(s):

Escherichia Coli ◽

Phylogenetic Analysis ◽

Resistance Gene ◽

Broiler Chickens ◽

Human Consumption ◽

E Coli ◽

Extended Spectrum ◽

First Time ◽

Pfge Profiles

We aimed to identify and characterize extended-spectrum β-lactamase (ESBL)-and/or plasmid-mediated AmpC β-lactamase (pAmpC)-producing Escherichia coli isolated from healthy broiler chickens slaughtered for human consumption in Korea. A total of 332 E. coli isolates were identified from 339 cloacal swabs in 2019. More than 90% of the isolates were resistant to multiple antimicrobials. ESBL/pAmpC-production was noted in 14% (46/332) of the isolates. Six of the CTX-M-β-lactamase-producing isolates were found to co-harbor at least one plasmid-mediated quinolone resistance gene. We observed the co-existence of blaCMY-2 and mcr-1 genes in the same isolate for the first time in Korea. Phylogenetic analysis demonstrated that the majority of blaCMY-2-carrying isolates belonged to subgroup D. Conjugation confirmed the transferability of blaCTX-M and blaCMY-2 genes, as well as non-β-lactam resistance traits from 60.9% (28/46) of the ESBL/pAmpC-producing isolates to a recipient E. coli J53. The ISECP, IS903, and orf477 elements were detected in the upstream or downstream regions. The blaCTX-M and blaCMY-2 genes mainly belonged to the IncI1, IncHI2, and/or IncFII plasmids. Additionally, the majority of ESBL/pAmpC-producing isolates exhibited heterogeneous PFGE profiles. This study showed that healthy chickens act as reservoirs of ESBL/pAmpC-producing E. coli that can potentially be transmitted to humans.

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Constitutive soxR Mutations Contribute to Multiple-Antibiotic Resistance in Clinical Escherichia coli Isolates

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.49.7.2746-2752.2005 ◽

2005 ◽

Vol 49 (7) ◽

pp. 2746-2752 ◽

Cited By ~ 63

Author(s):

Anastasia Koutsolioutsou ◽

Samuel Peña-Llopis ◽

Bruce Demple

Keyword(s):

Nitric Oxide ◽

Escherichia Coli ◽

Antibiotic Resistance ◽

Dna Sequences ◽

Single Point ◽

Constitutive Expression ◽

Clinical Isolates ◽

Multiple Antibiotic Resistance ◽

E Coli ◽

First Time

ABSTRACT The soxRS regulon of Escherichia coli and Salmonella enterica is induced by redox-cycling compounds or nitric oxide and provides resistance to superoxide-generating agents, macrophage-generated nitric oxide, antibiotics, and organic solvents. We have previously shown that constitutive expression of soxRS can contribute to quinolone resistance in clinically relevant S. enterica. In this work, we have carried out an analysis of the mechanism of constitutive soxS expression and its role in antibiotic resistance in E. coli clinical isolates. We show that constitutive soxS expression in three out of six strains was caused by single point mutations in the soxR gene. The mutant SoxR proteins contributed to the multiple-antibiotic resistance phenotypes of the clinical strains and were sufficient to confer multiple-antibiotic resistance in a fresh genetic background. In the other three clinical isolates, we observed, for the first time, that elevated soxS expression was not due to mutations in soxR. The mechanism of such increased soxS expression remains unclear. The same E. coli clinical isolates harbored polymorphic soxR and soxS DNA sequences, also seen for the first time.

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