scholarly journals Characterization of an Acidic-pH-Inducible Stress Protein (hsp70), a Putative Sulfatide Binding Adhesin, fromHelicobacter pylori

1998 ◽  
Vol 66 (9) ◽  
pp. 4061-4067 ◽  
Author(s):  
Mario Huesca ◽  
Avery Goodwin ◽  
Arianna Bhagwansingh ◽  
Paul Hoffman ◽  
Clifford A. Lingwood
Keyword(s):  
Stress Protein ◽  
Acid Stress ◽  
Binding Specificity ◽  
Low Ph ◽  
Bacterial Surface ◽  
Dna Library ◽  
H Pylori

ABSTRACT The in vitro glycolipid binding specificity of the gastric pathogenHelicobacter pylori is altered to include sulfated glycolipids (sulfatides) following brief exposure of the organism to acid pH typical of the stomach. This change is prevented by anti-hsp70 antibodies, suggesting that hsp70 may be a stress-induced surface adhesin, mediating sulfatide recognition. To facilitate investigation of the role of hsp70 in attachment, we have cloned and sequenced theH. pylori hsp70 gene (dnaK). Thehsp70 gene was identified by probing a cosmid DNA library made from H. pylori 439 with a PCR amplicon generated with oligonucleotides synthesized to highly conserved regions ofdnaK. The 1.9-kb H. pylori hsp70 gene encodes a product of 616 amino acids. Primer extension analysis revealed a single transcription start site, while Northern blot analysis established that hsp70 was preferentially induced by low pH rather than by heat shock. The ability ofH. pylori to alter its glycolipid binding specificity following exposure to low pH by upregulating hsp70 and by expressing hsp70 on the bacterial surface may provide a survival advantage during periods of high acid stress.

scholarly journals Differential Requirements for VirB1 and VirB2 during Brucella abortus Infection

2004 ◽  
Vol 72 (9) ◽  
pp. 5143-5149 ◽  
Author(s):  
Andreas B. den Hartigh ◽  
Yao-Hui Sun ◽  
David Sondervan ◽  
Niki Heuvelmans ◽  
Marjolein O. Reinders ◽  
...  
Keyword(s):  
Mouse Model ◽  
Brucella Abortus ◽  
Persistent Infection ◽  
Host Cells ◽  
Intracellular Replication ◽  
Bacterial Surface ◽  
Type Iv

ABSTRACT The Brucella abortus virB operon, encoding a type IV secretion system (T4SS), is required for intracellular replication and persistent infection in the mouse model. The products of the first two genes of the virB operon, virB1 and virB2, are predicted to be localized at the bacterial surface, where they could potentially interact with host cells. Studies to date have focused on characterization of transposon mutations in these genes, which are expected to exert polar effects on downstream genes in the operon. In order to determine whether VirB1 and VirB2 are required for the function of the T4SS apparatus, we constructed and characterized nonpolar deletion mutations of virB1 and virB2. Both mutants were shown to be nonpolar, as demonstrated by their ability to express the downstream gene virB5 during stationary phase of growth in vitro. Both VirB1 and VirB2 were essential for intracellular replication in J774 macrophages. The nonpolar virB2 mutant was unable to cause persistent infection in the mouse model, demonstrating the essential role of VirB2 in the function of the T4SS apparatus during infection. In contrast, the nonpolar virB1 mutant persisted at wild-type levels, showing that the function of VirB1 is dispensable in the mouse model of persistent infection.

Role of vitamin C in gastric cancer

2018 ◽  
Vol 01 (1) ◽  
Author(s):  
Takalkar U Vidyadhar
Keyword(s):  
Gastric Cancer ◽  
Vitamin C ◽  
Gastric Juice ◽  
Oxidative Dna Damage ◽  
Preventive Measure ◽  
Dietary Factors ◽  
Preventive Strategy ◽  
H Pylori

Gastric cancer is a multifactorial disease with complex interplay of environmental and genetic factors. Helicobacter pylori (H. pylori) infestation has been identified as the most important etiological agent in the pathogenesis of gastric cancer. Also, the role of dietary factors that is low consumption of fruits and vegetables have been found to be associated with gastric cancer. Among the dietary factors, antioxidants especially vitamin C has been found to confer the strongest protection against gastric cancer. Its anti-proliferative and pro-apoptotic action has been suggested in vitro. Because of its antioxidant activity, it protects cells against oxidative DNA damage caused by toxic effects of reactive oxygen species. It also inhibits production of carcinogenic N-nitroso compound in the stomach. The person with H. pylori infection has low levels of vitamin C in their gastric juice and levels of vitamin C normalizes on eradication of H. pylori. Vitamin C levels are high in gastric mucosa and gastric juice, sometimes more than that of in plasma. But gastric pathological conditions cause lowered secretion of vitamin C into gastric juice. Effect of H. pylori on vitamin C in gastric juice is reversible and on eradication of H. pylori, it returns to normal level. Hence, eradication of H. pylori and chemoprevention with antioxidant supplementation will be an effective preventive strategy to reduce the incidence of gastric cancer and related mortality. Vitamin C and gastric cancer is an area of potential interest for researchers as a preventive measure. Keywords: Vitamin C, H. pylori, gastric cancer.

scholarly journals Characterization of a Dye-Decolorizing Peroxidase from Irpex lacteus Expressed in Escherichia coli: An Enzyme with Wide Substrate Specificity Able to Transform Lignosulfonates

2021 ◽  
Vol 7 (5) ◽  
pp. 325
Author(s):  
Laura Isabel de de Eugenio ◽  
Rosa Peces-Pérez ◽  
Dolores Linde ◽  
Alicia Prieto ◽  
Jorge Barriuso ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Inclusion Bodies ◽  
Veratryl Alcohol ◽  
Dye Decolorization ◽  
Irpex Lacteus ◽  
Type D ◽  
Lignin Peroxidases

A dye-decolorizing peroxidase (DyP) from Irpex lacteus was cloned and heterologously expressed as inclusion bodies in Escherichia coli. The protein was purified in one chromatographic step after its in vitro activation. It was active on ABTS, 2,6-dimethoxyphenol (DMP), and anthraquinoid and azo dyes as reported for other fungal DyPs, but it was also able to oxidize Mn2+ (as manganese peroxidases and versatile peroxidases) and veratryl alcohol (VA) (as lignin peroxidases and versatile peroxidases). This corroborated that I. lacteus DyPs are the only enzymes able to oxidize high redox potential dyes, VA and Mn+2. Phylogenetic analysis grouped this enzyme with other type D-DyPs from basidiomycetes. In addition to its interest for dye decolorization, the results of the transformation of softwood and hardwood lignosulfonates suggest a putative biological role of this enzyme in the degradation of phenolic lignin.

scholarly journals Effect of Helicobacter pylori on Polymorphonuclear Leukocyte Migration across Polarized T84 Epithelial Cell Monolayers: Role of Vacuolating Toxin VacA and cagPathogenicity Island

2000 ◽  
Vol 68 (9) ◽  
pp. 5225-5233 ◽  
Author(s):  
Véronique Hofman ◽  
Vittorio Ricci ◽  
Antoine Galmiche ◽  
Patrick Brest ◽  
Patrick Auberger ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Polymorphonuclear Leukocyte ◽  
Broth Culture ◽  
Intestinal Cell ◽  
T84 Cells ◽  
Vacuolating Cytotoxin ◽  
Intestinal Cell Line ◽  
H Pylori

ABSTRACT Helicobacter pylori infection can induce polymorphonuclear leukocyte (PMNL) infiltration of the gastric mucosa, which characterizes acute chronic gastritis. The mechanisms underlying this process are poorly documented. The lack of an in vitro model has considerably impaired the study of transepithelial migration of PMNL induced by H. pylori. In the present work, we used confluent polarized monolayers of the human intestinal cell line T84 grown on permeable filters to analyze the epithelial PMNL response induced by broth culture filtrates (BCFs) and bacterial suspensions from different strains of H. pylori. We have evaluated the role of the vacuolating cytotoxin VacA and of the cagpathogenicity island (PAI) of H. pylori in PMNL migration via their effects on T84 epithelial cells. We noted no difference in the rates of PMNL transepithelial migration after epithelial preincubation with bacterial suspensions or with BCFs of VacA-negative or VacA-positive H. pylori strains. In contrast, PMNL transepithelial migration was induced after incubation of the T84 cells with cag PAI-positive and cagE-positiveH. pylori strains. Finally, PMNL migration was correlated with a basolateral secretion of interleukin-8 by T84 cells, thus creating a subepithelial chemotactic gradient for PMNL. These data provide evidence that the vacuolating cytotoxin VacA is not involved in PMNL transepithelial migration and that the cag PAI, with a pivotal role for the cagE gene, provokes a transcellular signal across T84 monolayers, inducing a subepithelial PMNL response.

Effect of temperature on transition and transversion mutagenesis: characterization of wild type and a mutator T4 DNA polymerase mutant

1984 ◽  
Vol 26 (3) ◽  
pp. 386-389 ◽  
Author(s):  
Linda J. Reha-Krantz ◽  
Sükran Parmaksizoglu
Keyword(s):  
Dna Polymerase ◽  
Low Temperatures ◽  
Bacteriophage T4 ◽  
Effect Of Temperature ◽  
In Vitro Mutagenesis ◽  
Wild Type ◽  
Mutational Site

The effect of temperature on genetically well-defined mutational pathways was examined in the bacteriophage T4. The mutational site was a T4 rII ochre mutant which could revert to rII+ via a transversion or to the amber convertant via a transition. Temperature did not strongly affect any of the pathways examined in a wild-type background; however, increased temperature reduced the mutational activity of a mutator DNA polymerase mutant. Possible models to explain the role of temperature in mutagenesis are discussed as well as the significance of low temperatures for in vitro mutagenesis reactions.Key words: bacteriophage T4, mutator, transition, transversion, temperature effects.

scholarly journals A Novel 3-Deoxy-d-manno-Octulosonic Acid (Kdo) Hydrolase That Removes the Outer Kdo Sugar of Helicobacter pylori Lipopolysaccharide

2005 ◽  
Vol 187 (10) ◽  
pp. 3374-3383 ◽  
Author(s):  
Christopher Stead ◽  
An Tran ◽  
Donald Ferguson ◽  
Sara McGrath ◽  
Robert Cotter ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Lipid A ◽  
In Vitro Assay ◽  
Spectrometric Analysis ◽  
Vitro Assay ◽  
The Core ◽  
H Pylori

ABSTRACT The lipid A domain anchors lipopolysaccharide (LPS) to the outer membrane and is typically a disaccharide of glucosamine that is both acylated and phosphorylated. The core and O-antigen carbohydrate domains are linked to the lipid A moiety through the eight-carbon sugar 3-deoxy-d-manno-octulosonic acid known as Kdo. Helicobacter pylori LPS has been characterized as having a single Kdo residue attached to lipid A, predicting in vivo a monofunctional Kdo transferase (WaaA). However, using an in vitro assay system we demonstrate that H. pylori WaaA is a bifunctional enzyme transferring two Kdo sugars to the tetra-acylated lipid A precursor lipid IVA. In the present work we report the discovery of a Kdo hydrolase in membranes of H. pylori capable of removing the outer Kdo sugar from Kdo2-lipid A. Enzymatic removal of the Kdo group was dependent upon prior removal of the 1-phosphate group from the lipid A domain, and mass spectrometric analysis of the reaction product confirmed the enzymatic removal of a single Kdo residue by the Kdo-trimming enzyme. This is the first characterization of a Kdo hydrolase involved in the modification of gram-negative bacterial LPS.

scholarly journals Structural Characterization of Charcoal Exposed to High and Low Ph: Implications for 14C Sample Preparation and Charcoal Preservation

Radiocarbon ◽  
2008 ◽  
Vol 50 (2) ◽  
pp. 289-307 ◽  
Author(s):  
N R Rebollo ◽  
I Cohen-Ofri ◽  
R Popovitz-Biro ◽  
O Bar-Yosef ◽  
L Meignen ◽  
...  
Keyword(s):  
Alkali Treatment ◽  
Low Ph ◽  
Upper Paleolithic ◽  
Salt Bridges ◽  
Weight Losses ◽  
The Reformation ◽  
Early Upper Paleolithic ◽  
Early Upper

Chemical and structural similarities between poorly preserved charcoal and its contaminants, as well as low radiocarbon concentrations in old samples, complicate 14C age determinations. Here, we characterize 4 fossil charcoal samples from the late Middle Paleolithic and early Upper Paleolithic strata of Kebara Cave, Israel, with respect to the structural and chemical changes that occur when they are subjected to the acid-base-acid (ABA) treatment. Differential thermal analysis and TEM show that acid treatment disrupts the structure, whereas alkali treatment results in the reformation of molecular aggregates. The major changes are ascribed to the formation of salt bridges at high pH and the disruption of the graphite-like crystallites at low pH. Weight losses during the treatments are consistently greater for older samples, implying that they are less well preserved. Based on the changes observed in vitro due to pH fluctuations, various methods for removing contamination, as well as a mechanism for preferential preservation of charcoal in nature, are proposed.

scholarly journals Characterization of the Urease Operon of Brucella abortus and Assessment of Its Role in Virulence of the Bacterium

2006 ◽  
Vol 75 (2) ◽  
pp. 774-780 ◽  
Author(s):  
Félix J. Sangari ◽  
Asunción Seoane ◽  
María Cruz Rodríguez ◽  
Jesús Agüero ◽  
Juan M. García Lobo
Keyword(s):  
Brucella Abortus ◽  
Urease Activity ◽  
Strong Acid ◽  
Oral Route ◽  
Open Reading Frames ◽  
Human Brucellosis ◽  
Major Route

ABSTRACT Most members of the genus Brucella show strong urease activity. However, the role of this enzyme in the pathogenesis of Brucella infections is poorly understood. We isolated several Tn5 insertion mutants deficient in urease activity from Brucella abortus strain 2308. The mutations of most of these mutants mapped to a 5.7-kbp DNA region essential for urease activity. Sequencing of this region, designated ure1, revealed the presence of seven open reading frames corresponding to the urease structural proteins (UreA, UreB, and UreC) and the accessory proteins (UreD, UreE, UreF, and UreG). In addition to the urease genes, another gene (cobT) was identified, and inactivation of this gene affected urease activity in Brucella. Subsequent analysis of the previously described sequences of the genomes of Brucella spp. revealed the presence of a second urease cluster, ure2, in all them. The ure2 locus was apparently inactive in B. abortus 2308. Urease-deficient mutants were used to evaluate the role of urease in Brucella pathogenesis. The urease-producing strains were found to be resistant in vitro to strong acid conditions in the presence of urea, while urease-negative mutants were susceptible to acid treatment. Similarly, the urease-negative mutants were killed more efficiently than the urease-producing strains during transit through the stomach. These results suggested that urease protects brucellae during their passage through the stomach when the bacteria are acquired by the oral route, which is the major route of infection in human brucellosis.

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