scholarly journals HasB, the Serratia marcescens TonB Paralog, Is Specific to HasR

2007 ◽  
Vol 190 (1) ◽  
pp. 21-27 ◽  
Author(s):  
Najla Benevides-Matos ◽  
Cécile Wandersman ◽  
Francis Biville
Keyword(s):  
Escherichia Coli ◽  
Serratia Marcescens ◽  
Molecular Mechanisms ◽  
Natural Host ◽  
Heme Uptake ◽  
E Coli ◽  
Transport Receptors ◽  
Tonb Protein ◽  
Specific Pair ◽  
Dependent Transport

ABSTRACT Serratia marcescens possesses two functional TonB paralogs, TonBSm and HasB, for energizing TonB-dependent transport receptors (TBDT). Previous work had shown that HasB is specific to heme uptake in the natural host and in Escherichia coli expressing the S. marcescens TBDT receptor HasR, whereas the S. marcescens TonB and E. coli TonB proteins function equally well with various TBDT receptors for heme and siderophores. This has raised the question of the target of this specificity. HasB could be specific either to heme TBDT receptors or only to HasR. To resolve this question, we have cloned in E. coli another S. marcescens heme receptor, HemR, and we show here that this receptor is TonB dependent and does not work with HasB. This demonstrates that HasB is not dedicated to heme TBDT receptors but rather forms a specific pair with HasR. This is the first reported case of a specific TonB protein working with only one TBDT receptor in one given species. We discuss the occurrence, possible molecular mechanisms, and selective advantages of such dedicated TonB paralogs.

scholarly journals Functional Differences between Heme Permeases: Serratia marcescens HemTUV Permease Exhibits a Narrower Substrate Specificity (Restricted to Heme) Than the Escherichia coli DppABCDF Peptide-Heme Permease

2008 ◽  
Vol 190 (6) ◽  
pp. 1866-1870 ◽  
Author(s):  
Sylvie Létoffé ◽  
Philippe Delepelaire ◽  
Cécile Wandersman
Keyword(s):  
Escherichia Coli ◽  
Serratia Marcescens ◽  
Outer Membrane Receptor ◽  
Heme Uptake ◽  
Periplasmic Binding Protein ◽  
E Coli ◽  
Iron Source ◽  
Functional Differences ◽  
Genes Encoding

ABSTRACT Serratia marcescens hemTUV genes encoding a potential heme permease were cloned in Escherichia coli recombinant mutant FB827 dppF::Km(pAM 238-hasR). This strain, which expresses HasR, a foreign heme outer membrane receptor, is potentially capable of using heme as an iron source. However, this process is invalidated due to a dppF::Km mutation which inactivates the Dpp heme/peptide permease responsible for heme, dipeptide, and δ-aminolevulinic (ALA) transport through the E. coli inner membrane. We show here that hemTUV genes complement the Dpp permease for heme utilization as an iron source and thus are functional in E. coli. However, hemTUV genes do not complement the Dpp permease for ALA uptake, indicating that the HemTUV permease does not transport ALA. Peptides do not inhibit heme uptake in vivo, indicating that, unlike Dpp permease, HemTUV permease does not transport peptides. HemT, the periplasmic binding protein, binds heme. Heme binding is saturable and not inhibited by peptides that inhibit heme uptake by the Dpp system. Thus, the S. marcescens HemTUV permease and, most likely, HemTUV orthologs present in many gram-negative pathogens form a class of heme-specific permeases different from the Dpp peptide/heme permease characterized in E. coli.

scholarly journals In Escherichia coli Ammonia Inhibits Cytochrome bo3 But Activates Cytochrome bd-I

Antioxidants ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 13
Author(s):  
Elena Forte ◽  
Sergey A. Siletsky ◽  
Vitaliy B. Borisov
Keyword(s):  
Escherichia Coli ◽  
Molecular Mechanisms ◽  
Dissociation Constants ◽  
Reductase Activity ◽  
Ammonia Concentration ◽  
High Concentration ◽  
E Coli ◽  
Cytochrome Bd ◽  
Cytochrome Bo3 ◽  
Oxygen Reductase

Interaction of two redox enzymes of Escherichia coli, cytochrome bo3 and cytochrome bd-I, with ammonium sulfate/ammonia at pH 7.0 and 8.3 was studied using high-resolution respirometry and absorption spectroscopy. At pH 7.0, the oxygen reductase activity of none of the enzymes is affected by the ligand. At pH 8.3, cytochrome bo3 is inhibited by the ligand, with 40% maximum inhibition at 100 mM (NH4)2SO4. In contrast, the activity of cytochrome bd-I at pH 8.3 increases with increasing the ligand concentration, the largest increase (140%) is observed at 100 mM (NH4)2SO4. In both cases, the effector molecule is apparently not NH4+ but NH3. The ligand induces changes in absorption spectra of both oxidized cytochromes at pH 8.3. The magnitude of these changes increases as ammonia concentration is increased, yielding apparent dissociation constants Kdapp of 24.3 ± 2.7 mM (NH4)2SO4 (4.9 ± 0.5 mM NH3) for the Soret region in cytochrome bo3, and 35.9 ± 7.1 and 24.6 ± 12.4 mM (NH4)2SO4 (7.2 ± 1.4 and 4.9 ± 2.5 mM NH3) for the Soret and visible regions, respectively, in cytochrome bd-I. Consistently, addition of (NH4)2SO4 to cells of the E. coli mutant containing cytochrome bd-I as the only terminal oxidase at pH 8.3 accelerates the O2 consumption rate, the highest one (140%) being at 27 mM (NH4)2SO4. We discuss possible molecular mechanisms and physiological significance of modulation of the enzymatic activities by ammonia present at high concentration in the intestines, a niche occupied by E. coli.

scholarly journals PERFIL DE SENSIBILIDADE A ANTIMICROBIANOS POR COMPONENTES DA MICROBIOTA BACTERIANA ORAL E RETAL DE PRIMATAS NÃO HUMANOS

2019 ◽  
Vol 20 ◽  
Author(s):  
Marcone Helmer Silva ◽  
Hilma Lúcia Tavares Dias ◽  
Ednaldo da Silva Filho ◽  
Sarah Raphaela Rocha de Azevedo Scalercio ◽  
Wellington Bandeira da Silva ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Serratia Marcescens ◽  
Proteus Mirabilis ◽  
Enterobacter Cloacae ◽  
Callithrix Jacchus ◽  
E Coli ◽  
Staphylococcus Xylosus

Resumo Os objetivos desta pesquisa foram identificar bactérias isoladas da cavidade oral e da ampola retal de Saimiri collinsi e Callithrix jacchus e determinar a sensibilidade a 16 antimicrobianos. Trinta indivíduos de cada espécie foram analisados e foram isoladas 136 bactérias em C. jacchus e 84 em S. collinsi. As bactérias isoladas em maior número em S. collinsi foram Klebsiella pneumoniae, Escherichia coli, Enterobacter cloacae, Raoutella ornithinolytica, Staphylococcus xylosus e Proteus mirabilis. As bactérias isoladas em C. jacchus foram K. pneumoniae, E. cloacae, E. coli, Serratia marcescens e S. xylosus na cavidade oral e ampola retal. O teste de sensibilidade mostrou que, dentre as cepas isoladas, os maiores percentuais de resistência foram observados para ampicilina, amoxicilina, cefalotina e nitrofurantoína. Na cavidade oral de ambas as espécies as cepas foram sensíveis à ceftazidima, ceftriaxona, meropenem, amicacina, levofloxacina e a sulfametoxazol/trimetoprim. Na ampola retal, as isoladas foram sensíveis à cefoxitina, ceftazidima, ceftriaxona, ertapenem, meropenem, amicacina e levofloxacina. Conclui-se que as espécies de S. collinsi e C. jacchus apresentam sua microbiota oral e retal composta por várias espécies bacterianas e que a resistência pode ser um problema no criatório, uma vez que as cepas mostraram percentuais elevados de resistência a diferentes antimicrobianos.

scholarly journals The Role of Metabolites in the Link between DNA Replication and Central Carbon Metabolism in Escherichia coli

Genes ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 447
Author(s):  
Klaudyna Krause ◽  
Monika Maciąg-Dorszyńska ◽  
Anna Wosinski ◽  
Lidia Gaffke ◽  
Joanna Morcinek-Orłowska ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Dna Replication ◽  
Protein Interactions ◽  
Carbon Metabolism ◽  
Molecular Mechanisms ◽  
Central Carbon Metabolism ◽  
Replication Initiation ◽  
Cell Physiology ◽  
E Coli ◽  
Central Carbon

A direct link between DNA replication regulation and central carbon metabolism (CCM) has been previously demonstrated in Bacillus subtilis and Escherichia coli, as effects of certain mutations in genes coding for replication proteins could be specifically suppressed by particular mutations in genes encoding CCM enzymes. However, specific molecular mechanism(s) of this link remained unknown. In this report, we demonstrate that various CCM metabolites can suppress the effects of mutations in different replication genes of E. coli on bacterial growth, cell morphology, and nucleoid localization. This provides evidence that the CCM-replication link is mediated by metabolites rather than direct protein-protein interactions. On the other hand, action of metabolites on DNA replication appears indirect rather than based on direct influence on the replication machinery, as rate of DNA synthesis could not be corrected by metabolites in short-term experiments. This corroborates the recent discovery that in B. subtilis, there are multiple links connecting CCM to DNA replication initiation and elongation. Therefore, one may suggest that although different in detail, the molecular mechanisms of CCM-dependent regulation of DNA replication are similar in E. coli and B. subtilis, making this regulation an important and common constituent of the control of cell physiology in bacteria.

scholarly journals Phenotypic Detection of Plasmid-Mediated Colistin Resistance in Enterobacteriaceae

2019 ◽  
Vol 58 (3) ◽  
Author(s):  
Edgar Gonzales Escalante ◽  
Katherine Yauri Condor ◽  
Jose A. Di Conza ◽  
Gabriel O. Gutkind
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Serratia Marcescens ◽  
Bacterial Growth ◽  
Screening Test ◽  
Colistin Resistance ◽  
Content Type ◽  
E Coli

ABSTRACT The aim of this work was to evaluate an easy-to-perform assay based upon inhibition of mobile colistin resistance (MCR) activity by EDTA. We included 92 nonrelated isolates of Enterobacteriaceae (74 Escherichia coli, 17 Klebsiella pneumoniae, and 1 Serratia marcescens). Our proposed method is based on a modification of the colistin agar-spot screening test (CAST), a plate containing 3 μg/ml colistin, by adding an extra plate of colistin agar-spot supplemented with EDTA (eCAST). Bacterial growth was evaluated after 24 h of incubation at 35°C. All the colistin-resistant isolates showed development on the CAST plates. Colistin-resistant K. pneumoniae without mcr-1 and S. marcescens also grew on the eCAST plates. In contrast, colistin-resistant MCR-producing E. coli was not able to grow in eCAST plates. The combined CAST/eCAST test could provide a simple and easy-to-perform method to differentiate MCR-producing Enterobacteriaceae from those in which colistin resistance is mediated by chromosomal mechanisms.

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 Transcriptional Responses of Escherichia coli K-12 and O157:H7 Associated with Lettuce Leaves

2012 ◽  
Vol 78 (6) ◽  
pp. 1752-1764 ◽  
Author(s):  
Ryan C. Fink ◽  
Elaine P. Black ◽  
Zhe Hou ◽  
Masayuki Sugawara ◽  
Michael J. Sadowsky ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Molecular Mechanisms ◽  
Leaf Surface ◽  
Short Term ◽  
Transcriptional Responses ◽  
Content Type ◽  
E Coli ◽  
Leaf Surfaces ◽  
K 12

ABSTRACTAn increasing number of outbreaks of gastroenteritis recently caused byEscherichia coliO157:H7 have been linked to the consumption of leafy green vegetables. Although it is known thatE. colisurvives and grows in the phyllosphere of lettuce plants, the molecular mechanisms by which this bacterium associates with plants are largely unknown. The goal of this study was to identifyE. coligenes relevant to its interaction, survival, or attachment to lettuce leaf surfaces, comparingE. coliK-12, a model system, andE. coliO157:H7, a pathogen associated with a large number of outbreaks. Using microarrays, we found that upon interaction with intact leaves, 10.1% and 8.7% of the 3,798 shared genes were differentially expressed in K-12 and O157:H7, respectively, whereas 3.1% changed transcript levels in both. The largest group of genes downregulated consisted of those involved in energy metabolism, includingtnaA(33-fold change), encoding a tryptophanase that converts tryptophan into indole. Genes involved in biofilm modulation (bhsAandybiM) and curli production (csgAandcsgB) were significantly upregulated inE. coliK-12 and O157:H7. BothcsgAandbhsA(ycfR) mutants were impaired in the long-term colonization of the leaf surface, but onlycsgAmutants had diminished ability in short-term attachment experiments. Our data suggested that the interaction ofE. coliK-12 and O157:H7 with undamaged lettuce leaves likely is initiated via attachment to the leaf surface using curli fibers, a downward shift in their metabolism, and the suppression of biofilm formation.

scholarly journals Transcriptomic Analysis of Escherichia coli O157:H7 and K-12 Cultures Exposed to Inorganic and Organic Acids in Stationary Phase Reveals Acidulant- and Strain-Specific Acid Tolerance Responses

2010 ◽  
Vol 76 (19) ◽  
pp. 6514-6528 ◽  
Author(s):  
Thea King ◽  
Sacha Lucchini ◽  
Jay C. D. Hinton ◽  
Kari Gobius
Keyword(s):  
Escherichia Coli ◽  
Hydrochloric Acid ◽  
Organic Acids ◽  
Stationary Phase ◽  
Molecular Mechanisms ◽  
Microbial Inactivation ◽  
Specific Response ◽  
Transcriptomic Response ◽  
E Coli ◽  
K 12

ABSTRACT The food-borne pathogen Escherichia coli O157:H7 is commonly exposed to organic acid in processed and preserved foods, allowing adaptation and the development of tolerance to pH levels otherwise lethal. Since little is known about the molecular basis of adaptation of E. coli to organic acids, we studied K-12 MG1655 and O157:H7 Sakai during exposure to acetic, lactic, and hydrochloric acid at pH 5.5. This is the first analysis of the pH-dependent transcriptomic response of stationary-phase E. coli. Thirty-four genes and three intergenic regions were upregulated by both strains during exposure to all acids. This universal acid response included genes involved in oxidative, envelope, and cold stress resistance and iron and manganese uptake, as well as 10 genes of unknown function. Acidulant- and strain-specific responses were also revealed. The acidulant-specific response reflects differences in the modes of microbial inactivation, even between weak organic acids. The two strains exhibited similar responses to lactic and hydrochloric acid, while the response to acetic acid was distinct. Acidulant-dependent differences between the strains involved induction of genes involved in the heat shock response, osmoregulation, inorganic ion and nucleotide transport and metabolism, translation, and energy production. E. coli O157:H7-specific acid-inducible genes were identified, suggesting that the enterohemorrhagic E. coli strain possesses additional molecular mechanisms contributing to acid resistance that are absent in K-12. While E. coli K-12 was most resistant to lactic and hydrochloric acid, O157:H7 may have a greater ability to survive in more complex acidic environments, such as those encountered in the host and during food processing.

scholarly journals Nickel Promotes Biofilm Formation by Escherichia coli K-12 Strains That Produce Curli

2009 ◽  
Vol 75 (6) ◽  
pp. 1723-1733 ◽  
Author(s):  
Claire Perrin ◽  
Romain Briandet ◽  
Gregory Jubelin ◽  
Philippe Lejeune ◽  
Marie-Andrée Mandrand-Berthelot ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Biofilm Formation ◽  
Molecular Mechanisms ◽  
Selective Advantage ◽  
Bacterial Survival ◽  
Toxic Compounds ◽  
E Coli ◽  
Transcriptional Effect ◽  
K 12 ◽  
Encoding Genes

ABSTRACT The survival of bacteria exposed to toxic compounds is a multifactorial phenomenon, involving well-known molecular mechanisms of resistance but also less-well-understood mechanisms of tolerance that need to be clarified. In particular, the contribution of biofilm formation to survival in the presence of toxic compounds, such as nickel, was investigated in this study. We found that a subinhibitory concentration of nickel leads Escherichia coli bacteria to change their lifestyle, developing biofilm structures rather than growing as free-floating cells. Interestingly, whereas nickel and magnesium both alter the global cell surface charge, only nickel promotes biofilm formation in our system. Genetic evidence indicates that biofilm formation induced by nickel is mediated by the transcriptional induction of the adhesive curli-encoding genes. Biofilm formation induced by nickel does not rely on efflux mechanisms using the RcnA pump, as these require a higher concentration of nickel to be activated. Our results demonstrate that the nickel-induced biofilm formation in E. coli is an adaptational process, occurring through a transcriptional effect on genes coding for adherence structures. The biofilm lifestyle is obviously a selective advantage in the presence of nickel, but the means by which it improves bacterial survival needs to be investigated.

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