YqiC of Salmonella enterica serovar Typhimurium is a membrane fusogenic protein required for mice colonization

Background  

Salmonella enterica serovar Typhimurium is an intracellular bacterial pathogen which can colonize a variety of hosts, including human, causing syndromes that vary from gastroenteritis and diarrhea to systemic disease.     

Coutilization of glucose and glycerol enhances the production of aromatic compounds in an Escherichia coli strain lacking the phosphoenolpyruvate: carbohydrate phosphotransferase system

Background  

Escherichia coli strains lacking the phosphoenolpyruvate: carbohydrate phosphotransferase system (PTS) are capable of coutilizing glucose and other carbon sources due to the absence of catabolite repression by glucose. In these strains, the lack of this important regulatory and transport system allows the coexistence of glycolytic and gluconeogenic pathways. Strains lacking PTS have been constructed with the goal of canalizing part of the phosphoenolpyruvate (PEP) not consumed in glucose transport to the aromatic pathway. The deletion of the ptsHIcrr operon inactivates PTS causing poor growth on this sugar; nonetheless, fast growing mutants on glucose have been isolated (PB12 strain). However, there are no reported studies concerning the growth potential of a PTS^- strain in mixtures of different carbon sources to enhance the production of aromatics compounds.     

Development of stable reporter system cloning <Emphasis Type="Italic">luxCDABE</Emphasis> genes into chromosome of <Emphasis Type="Italic">Salmonella enterica</Emphasis> serotypes using Tn7 transposon

Background  

Salmonellosis may be a food safety problem when raw food products are mishandled and not fully cooked. In previous work, we developed bioluminescent Salmonella enterica serotypes using a plasmid-based reporting system that can be used for real-time monitoring of the pathogen's growth on food products in short term studies. In this study, we report the use of a Tn7-based transposon system for subcloning of luxCDABE genes into the chromosome of eleven Salmonella enterica serotypes isolated from the broiler production continuum.     

Adaptation of <Emphasis Type="Italic">Salmonella enterica</Emphasis> Hadar under static magnetic field: effects on outer membrane protein pattern

Background  

Salmonella enterica serovar Hadar (S. Hadar) is a highly prevalent foodborne pathogen and therefore a major cause of human gastroenteritis worldwide. Outer membrane proteins whose production is often regulated by environmental conditions also play important roles in the adaptability of bacterial pathogens to various environments.     

Involvement of SPI-2-encoded SpiC in flagellum synthesis in Salmonella enterica serovar Typhimurium

Background  

SpiC encoded within Salmonella pathogeniCity island 2 on the Salmonella enterica serovar Typhimurium chromosome is required for survival within macrophages and systemic infection in mice. Additionally, SpiC contributes to Salmonella-induced activation of the signal transduction pathways in macrophages by affecting the expression of FliC, a component of flagella filaments. Here, we show the contribution of SpiC in flagellum synthesis.     

DNA microarray analysis of <Emphasis Type="Italic">Salmonella</Emphasis> serotype Typhimurium strains causing different symptoms of disease

Background  

Salmonella enterica subsp. enterica is one of the leading food-borne pathogens in the USA and European countries. Outcome of human Salmonella serotype Typhimurium infections ranges from mild self-limiting diarrhoea to severe diarrhoea that requires hospitalization. Increased knowledge of the mechanisms that are responsible for causing infection and especially the severity of infection is of high interest.     

Characterisation and expression of a PP1 serine/threonine protein phosphatase (PfPP1) from the malaria parasite, <Emphasis Type="Italic">Plasmodium falciparum:</Emphasis> demonstration of its essential role using RNA interference

Background  

Reversible protein phosphorylation is relatively unexplored in the intracellular protozoa of the Apicomplexa family that includes the genus Plasmodium, to which belong the causative agents of malaria. Members of the PP1 family represent the most highly conserved protein phosphatase sequences in phylogeny and play essential regulatory roles in various cellular pathways. Previous evidence suggested a PP1-like activity in Plasmodium falciparum, not yet identified at the molecular level.     

<Emphasis Type="Italic">Brucella melitensis</Emphasis> VjbR and C<Subscript>12</Subscript>-HSL regulons: contributions of the <Emphasis Type="Italic">N</Emphasis>-dodecanoyl homoserine lactone signaling molecule and LuxR homologue VjbR to gene expression

Background  

Quorum sensing is a communication system that regulates gene expression in response to population density and often regulates virulence determinants. Deletion of the luxR homologue vjbR highly attenuates intracellular survival of Brucella melitensis and has been interpreted to be an indication of a role for QS in Brucella infection. Confirmation for such a role was suggested, but not confirmed, by the demonstrated in vitro synthesis of an auto-inducer (AI) by Brucella cultures. In an effort to further delineate the role of VjbR to virulence and survival, gene expression under the control of VjbR and AI was characterized using microarray analysis.     

Functional dissection of translocon proteins of the <Emphasis Type="Italic">Salmonella</Emphasis> Pathogenicity Island 2-encoded type III secretion system

Background  

Type III secretion systems (T3SS) are essential virulence factors of most Gram-negative bacterial pathogens. T3SS deliver effector proteins directly into the cytoplasm of eukaryotic target cells and for this function, the insertion of a subset of T3SS proteins into the target cell membrane is important. These proteins form hetero-oligomeric pores acting as translocon for the delivery of effector proteins. Salmonella enterica is a facultative intracellular pathogen that uses the Salmonella Pathogenicity Island 2 (SPI2)-encoded T3SS to manipulate host cells in order to survive and proliferate within the Salmonella-containing vacuole of host cells. Previous work showed that SPI2-encoded SseB, SseC and SseD act to form the translocon of the SPI2-T3SS.     

Rapid screening of <Emphasis Type="Italic">Salmonella enterica</Emphasis>serovars Enteritidis,Hadar, Heidelberg and Typhimurium using a serologically-correlative allelotyping PCR targeting the O and H antigen alleles

Background  

Classical Salmonella serotyping is an expensive and time consuming process that requires implementing a battery of O and H antisera to detect 2,541 different Salmonella enterica serovars. For these reasons, we developed a rapid multiplex polymerase chain reaction (PCR)-based typing scheme to screen for the prevalent S. enterica serovars Enteritidis, Hadar, Heidelberg, and Typhimurium.     

Calcium transport and homeostasis in gill cells of a freshwater crab Dilocarcinus pagei

Crustaceans present a very interesting model system to study the process of calcification and calcium (Ca²⁺) transport because of molting-related events and the deposition of CaCO₃ in the new exoskeleton. Dilocarcinus pagei, a freshwater crab endemic to Brazil, was studied to understand Ca²⁺ transport in whole gill cells using a fluorescent probe. Cells were dissociated, all of the gill cell types were loaded with fluo-3 and intracellular Ca²⁺ change was monitored by adding Ca as CaCl₂ (0, 0.1, 0.25, 0.50, 1.0 and 5 mM), with a series of different inhibitors. For control gill cells, Ca²⁺ transport followed Michaelis–Menten kinetics with K _m = 0.42 ± 0.04 mM and V _max = 0.50 ± 0.02 μM (Ca²⁺ change × initial intracellular Ca⁻¹ × 180 s⁻¹; N = 14, r ² = 0.99). Verapamil (a Ca²⁺ channel inhibitor) and amiloride (a Na⁺/Ca²⁺ exchanger [NCX] inhibitor) completely reduced intracellular Ca²⁺ transport, while nifedipine, another Ca²⁺ channel inhibitor, did not. Vanadate, a plasma membrane Ca²⁺-ATPase inhibitor (PMCA), increased intracellular Ca²⁺ in gill cells through a decrease in the efflux of Ca²⁺. Ouabain increased intracellular Ca²⁺, similar to the effect of KB-R, a specific NCX inhibitor for Ca²⁺ in the influx mode. Alterations in extracellular [Na] in the saline did not affect intracellular Ca²⁺ transport. Caffeine, responsible for inducing Ca release from sarcoplasmic reticulum in vertebrate muscle, increased intracellular Ca²⁺ compared to control, suggesting an effect of this inhibitor in gill epithelial cells of Dilocarcinus pagei, probably through release of intracellular stores. We also demonstrate here that intracellular Ca²⁺ in gill cells of Dilocarcinus pagei was kept relatively constant in face of an extracellular Ca concentration of 50-fold, suggesting that crustaceans are able to display Ca²⁺ homeostasis through various Ca²⁺ intracellular sequestration mechanisms and/or plasma membrane Ca²⁺ influx and outflux that are highly regulatory. In summary, studies using whole gill cells are an interesting approach for working with real regulatory Ca²⁺ mechanisms in intact cells under physiological Ca levels (mM range), compared to earlier work using isolated vesicles of various epithelial cells.     

The control of CD4<Superscript>+</Superscript>CD25<Superscript>+</Superscript>Foxp3<Superscript>+</Superscript>regulatory T cell survival

   

CD4⁺CD25⁺Foxp3⁺ regulatory T (T_reg) cells are believed to play an important role in suppressing autoimmunity and maintaining peripheral tolerance. How their survival is regulated in the periphery is less clear. Here we show that T_reg cells express receptors for gamma chain cytokines and are dependent on an exogenous supply of these cytokines to overcome cytokine withdrawal apoptosis in vitro. This result was validated in vivo by the accumulation of T_reg cells in Bim^-/- and Bcl-2 tg mice which have arrested cytokine deprivation apoptosis. We also found that CD25 and Foxp3 expression were down-regulated in the absence of these cytokines. CD25⁺ cells from Scurfy mice do not depend on cytokines for survival demonstrating that Foxp3 increases their dependence on cytokines by suppressing cytokine production in T_reg cells. Our study reveals that the survival of T_reg cells is strictly dependent on cytokines and cytokine producing cells because they do not produce cytokines. Our study thus, demonstrates that different gamma chain cytokines regulate T_reg homeostasis in the periphery by differentially regulating survival and proliferation. These findings may shed light on ways to manipulate T_reg cells that could be utilized for their therapeutic applications.     

Eradication of <Emphasis Type="Italic">Salmonella</Emphasis> Typhimurium infection in a murine model of typhoid fever with the combination of probiotic <Emphasis Type="Italic">Lactobacillus fermentum</Emphasis> ME-3 and ofloxacin

Background  

The aim of the study was to detect whether in experimental Salmonella enterica Typhimurium infection the probiotic Lactobacillus fermentum ME-3 in combination with fluoroquinolone therapy would eradicate S. Typhimurium, prevent the development of liver and spleen granulomas and improve the indices of oxidative stress in the ileum mucosa.     

Antimicrobial activity of copper surfaces against suspensions of <Emphasis Type="Italic">Salmonella enterica</Emphasis> and <Emphasis Type="Italic">Campylobacter jejuni</Emphasis>

Background  

Salmonella enterica and Campylobacter jejuni are amongst the more prevalent bacterial pathogens that cause foodborne diseases. These microorganisms are common contaminants of poultry and poultry products. This study was aimed to evaluate the antibacterial activity of metallic copper surfaces on these important enteropathogens, and to determine the potential acquisition of copper by food exposed to this metal.     

The structure of a reduced form of OxyR from <Emphasis Type="Italic">Neisseria meningitidis</Emphasis>

Background  

Survival of the human pathogen, Neisseria meningitidis, requires an effective response to oxidative stress resulting from the release of hydrogen peroxide by cells of the human immune system. In N. meningitidis, expression of catalase, which is responsible for detoxifying hydrogen peroxide, is controlled by OxyR, a redox responsive LysR-type regulator. OxyR responds directly to intracellular hydrogen peroxide through the reversible formation of a disulphide bond between C199 and C208 in the regulatory domain of the protein.     

The Escherichia coli BarA-UvrY two-component system is a virulence determinant in the urinary tract

Background  

The Salmonella enterica BarA-SirA, the Erwinia carotovora ExpS-ExpA, the Vibrio cholerae BarA-VarA and the Pseudomonas spp GacS-GacA all belong to the same orthologous family of two-component systems as the Escherichia coli BarA-UvrY. In the first four species it has been demonstrated that disruption of this two-component system leads to a clear reduction in virulence of the bacteria. Our aim was to determine if the Escherichia coli BarA-UvrY two-component system is connected with virulence using a monkey cystitis model.