Genomic and proteomic characterization of two strains of Shigella flexneri 2 isolated from infants' stool samples in Argentina.

Background: Shigella specie is a globally important intestinal pathogen disseminated all over the world. In this study we analyzed the genome and the proteomic component of two Shigella flexneri 2a clinical isolates, collected from pediatric patients with gastroenteritis of the Northwest region of Argentina (NWA) in two periods of time, with four years of difference. Our goal was to determine putative changes at molecular levels occurred during these four years, that could explain the presence of this Shigella`s serovar as the prevalent pathogen in the population under study.

Epidemiological study of prevalent pathogens in the Northwest region of Argentina (NWA).

Northwest Argentina (NWA) is a poor economic-geographical region, with the highest rate of diarrhea diseases. At the moment, there are no reports showing the epidemiological status of this region that would allow to establish methods for prevention and control of these infections and to indicate of the prevalent pathogen that produces them. Therefore we carried out an epidemiological study of the gastroenteritis etiological agents and their incidence in the pediatric population.

Stability of the Typhimurium mutant under different stress conditions.

The virulence genes of are modulated during infection by several regulatory systems, and the RcsCDB system is one of the most important of these. The . Typhimurium EG14873 () strain harbours the point mutation, displaying a constitutive activation of this system, which is characterized by mucoid colonies and attenuated virulence phenotypes.

RcsB-dependent effects on nar operon regulation during the aerobic growth of Salmonella Typhimurium.

The intracellular pathogen Salmonella is an important cause of human foodborne diseases worldwide. Salmonella takes advantage of the phosphorelay regulatory systems to survive in the hostile environment of the host's gastrointestinal tract. It has been reported that the nitrate reductase Z (NR-Z), encoded by the narUZYV operon, is required during Salmonella transition to anaerobic environments and is constitutively produced at low levels, but little is known about the regulatory mechanism involved in the operon gene expression.

Transcriptional regulation of the fimbrial operon by the RcsCDB system.

In serovar Typhimurium, the RcsCDB regulatory system controls the expression of genes involved in synthesis of colanic acid, formation of flagella and virulence. Here, we show that activation of the RcsCDB system downregulates expression of an operon that encodes fimbriae involved in attachment to the mucus layer in the large intestine. Bioinformatic analysis predicts the existence of an RcsB-binding site located 180 bp upstream to the +1 transcription start site of the promoter, and electrophoretic mobility shift assays confirm that RcsB binds the promoter region .

Cross-talk between the RcsCDB and RstAB systems to control STM1485 gene expression in Salmonella Typhimurium during acid-resistance response.

Bacterial survive and respond to adverse changes in the environment by regulating gene transcription through two-component regulatory systems. In Salmonella Typhimurium the STM1485 gene expression is induced under low pH (4.5) during replication inside the epithelial host cell, but it is not involved in sensing or resisting to this condition.

Regulatory Effect of SlyA on Expression in Serovar Typhimurium.

The serovar Typhimurium RcsCDB system regulates the synthesis of colanic acid and the flagellum as well as the expression of virulence genes. We previously demonstrated that the mutant, which constitutively activates the RcsB regulator, attenuates virulence in an animal model. This attenuated phenotype was also produced by deletion of the gene.

The RcsCDB regulatory system plays a crucial role in the protection of Salmonella enterica serovar Typhimurium against oxidative stress.

Dps, the most abundant protein during the stationary growth phase, in Salmonella enterica is required for resistance to reactive oxygen species produced by the host during infection. It has been reported that in Salmonella dps expression is controlled by RpoS and Fur proteins. However, the regulation and function of Dps remain to be resolved.

A novel insight on signal transduction mechanism of RcsCDB system in Salmonella enterica serovar typhimurium.

The RcsCDB system of Salmonella enterica serovar Typhimurium is implicated in the control of capsule and flagella synthesis. The hybrid sensor RcsC, the phosphotransferase RcsD and the RcsB regulator, constitute the main components of the RcsCDB system. The proposed Rcs signaling cascade involves the autophosphorylation of RcsC and the transfer of the phosphate group to RcsB, mediated by RcsD.

Macrophage environment turns otherwise MccJ25-resistant Salmonella into sensitive.

Background: Microcin J25 (MccJ25) is a plasmid-encoded antibiotic peptide produced by Escherichia coli (E. coli). MccJ25 enters into the sensitive E.

The PmrAB system-inducing conditions control both lipid A remodeling and O-antigen length distribution, influencing the Salmonella Typhimurium-host interactions.

The Salmonella enterica serovar Typhimurium lipopolysaccharide consisting of covalently linked lipid A, non-repeating core oligosaccharide, and the O-antigen polysaccharide is the most exposed component of the cell envelope. Previous studies demonstrated that all of these regions act against the host immunity barrier. The aim of this study was to define the role and interaction of PmrAB-dependent gene products required for the lipopolysaccharide component synthesis or modification mainly during the Salmonella infection.

The PmrA/PmrB regulatory system controls the expression of the wzzfepE gene involved in the O-antigen synthesis of Salmonella enterica serovar Typhimurium.

The degree of polymerization of O-antigen from Salmonella enterica serovar Typhimurium is controlled by the products of the wzz(s)(t) and wzz(fepE) genes. In the present study we investigated the role of the PmrA/PmrB regulatory system in wzz(fepE) transcription. We report that the direct binding of the PmrA regulator to a specific promoter site induces the expression of the wzz(fepE) gene.

Sensitization of microcin J25-resistant strains by a membrane-permeabilizing peptide.

Microcin J25 (MccJ25) is a plasmid-encoded, 21-amino-acid, antibacterial peptide produced by Escherichia coli. MccJ25 inhibits RNA polymerase and the membrane respiratory chain. MccJ25 uptake into E.

The tolC locus affects the expression of sbmA through σE activity increase.

The SbmA protein is involved in the transport of MccB17-, MccJ25-, bleomycin- and proline-rich peptides into the Escherichia coli cytoplasm. sbmA gene homologues were found in a variety of bacteria. However, the physiological role of this protein still remains unknown.

Transcriptional autoregulation of the RcsCDB phosphorelay system in Salmonella enterica serovar Typhimurium.

The RcsCDB (Rcs) phosphorelay system is involved in the regulation of many envelope genes, such as those responsible for capsule synthesis, flagella production and O-antigen chain length, as well as in other cellular activities of several enteric bacteria. The system is composed of three proteins: the sensor RcsC, the response regulator RcsB, and the phospho-transfer intermediary protein RcsD. Previously, we reported two important aspects of this system: (a) rcsB gene expression is under the control of P(rcsDB) and P(rcsB) promoters, and (b) rcsD gene transcription decreases when the bacteria reach high levels of the RcsB regulator.

Delivery of cytosolic components by autophagic adaptor protein p62 endows autophagosomes with unique antimicrobial properties.

Autophagy allows cells to self-digest portions of their own cytoplasm for a multitude of physiological purposes, including innate and adaptive immunity functions. In one of its innate immunity manifestations, autophagy, is known to contribute to the killing of intracellular microbes, including Mycobacterium tuberculosis, although the molecular mechanisms have been unclear. Here, we delineated sequential steps of the autophagic pathway necessary to control intracellular M.

Identification of a new promoter for the response regulator rcsB expression in Salmonella enterica serovar Typhimurium.

The RcsCDB (Rcs) phosphorelay system regulates capsule synthesis, flagella production and other cellular activities in several enteric bacteria. This system consists of three proteins: the sensor RcsC, the cognate response regulator RcsB and the histidine-containing phosphotransfer protein RcsD (YojN), which is hypothesized to act as an intermediary in the phosphotransfer from RcsC to RcsB. The rcsC gene is convergently transcribed toward rcsB, which follows rcsD in what appears to be a two-gene operon.

Control of autophagy initiation by phosphoinositide 3-phosphatase Jumpy.

The majority of studies on autophagy, a cytoplasmic homeostasis pathway of broad biological and medical significance, have been hitherto focused on the phosphatidylinositol 3-kinases as the regulators of autophagy. Here, we addressed the reverse process driven by phosphoinositide phosphatases and uncovered a key negative regulatory role in autophagy of a phosphatidylinositol 3-phosphate (PI3P) phosphatase Jumpy (MTMR14). Jumpy associated with autophagic isolation membranes and early autophagosomes, defined by the key factor Atg16 necessary for proper localization and development of autophagic organelles.

Monitoring autophagy during Mycobacterium tuberculosis infection.

Tuberculosis is one of the world's most prevalent infectious diseases. The causative agent, M. tuberculosis, asymptomatically infects more than 30% of the world population and causes 8 million cases of active disease and 2 million deaths annually.

Autophagosome-independent essential function for the autophagy protein Atg5 in cellular immunity to intracellular pathogens.

The physiologic importance of autophagy proteins for control of mammalian bacterial and parasitic infection in vivo is unknown. Using mice with granulocyte- and macrophage-specific deletion of the essential autophagy protein Atg5, we show that Atg5 is required for in vivo resistance to the intracellular pathogens Listeria monocytogenes and Toxoplasma gondii. In primary macrophages, Atg5 was required for interferongamma (IFN-gamma)/LPS-induced damage to the T.

Toll-like receptors control autophagy.

Autophagy is a newly recognized innate defense mechanism, acting as a cell-autonomous system for elimination of intracellular pathogens. The signals and signalling pathways inducing autophagy in response to pathogen invasion are presently not known. Here we show that autophagy is controlled by recognizing conserved pathogen-associated molecular patterns (PAMPs).

Nonclassical pathway of Pseudomonas aeruginosa DNA-induced interleukin-8 secretion in cystic fibrosis airway epithelial cells.

Pseudomonas aeruginosa is a critical colonizer of the respiratory tract in cystic fibrosis. The chronic infections with this microorganism contribute to excessive inflammation and progressive lung damage in cystic fibrosis patients. The full repertoire of Pseudomonas products that promote inflammation in the cystic fibrosis lung is not known.

The PmrA/PmrB and RcsC/YojN/RcsB systems control expression of the Salmonella O-antigen chain length determinant.

The lipopolysaccharide (LPS) is the outermost component of the cell envelope in Gram-negative bacteria. It consists of the hydrophobic lipid A, a short non-repeating core oligosaccharide and a distal polysaccharide termed O-antigen. We report here that the PmrA/PmrB and RcsC/YojN/RcsB two-component systems of Salmonella enterica serovar Typhimurium independently promote transcription of the wzzst gene, which encodes a protein that determines the chain length of the O-antigen.

YojI of Escherichia coli functions as a microcin J25 efflux pump.

In the present study, we showed that yojI, an Escherichia coli open reading frame with an unknown function, mediates resistance to the peptide antibiotic microcin J25 when it is expressed from a multicopy vector. Disruption of the single chromosomal copy of yojI increased sensitivity of cells to microcin J25. The YojI protein was previously assumed to be an ATP-binding-cassette-type exporter on the basis of sequence similarities.