Transposon mutagenesis of probiotic Lactobacillus casei identifies asnH, an asparagine synthetase gene involved in its immune-activating capacity.

Lactobacillus casei ATCC 27139 enhances host innate immunity, and the J1 phage-resistant mutants of this strain lose the activity. A transposon insertion mutant library of L. casei ATCC 27139 was constructed, and nine J1 phage-resistant mutants out of them were obtained.

Salmonella type III effector SpvC, a phosphothreonine lyase, contributes to reduction in inflammatory response during intestinal phase of infection.

Salmonella phosphothreonine lyase SpvC inactivates the dual-phosphorylated host mitogen-activated protein kinases (MAPK) through β-elimination. While SpvC can be secreted in vitro by both Salmonella pathogenicity island (SPI)-1 and SPI-2 type III secretion systems (T3SSs), translocation of this protein into the host cell cytosol has only been demonstrated by SPI-2 T3SS. In this study, we show that SpvC can be delivered into the host cell cytoplasm by both SPI-1 and SPI-2 T3SSs.

Evaluation of Salmonella enterica serovar Typhimurium and Choleraesuis slyA mutant strains for use in live attenuated oral vaccines.

SlyA protein plays a key role in virulence in Salmonella enterica. In this study, we evaluated the ability of the slyA mutant strain of S. enterica serovar Choleraesuis (S.

The Chromobacterium violaceum type III effector CopE, a guanine nucleotide exchange factor for Rac1 and Cdc42, is involved in bacterial invasion of epithelial cells and pathogenesis.

The type III secretion system (T3SS) encoded by Chromobacterium pathogenicity islands 1 and 1a (Cpi-1/-1a) is critical for Chromobacterium violaceum pathogenesis. T3SS-dependent virulence is commonly characterized by type III effector virulence function, but the full repertoire of the effector proteins of Cpi-1/-1a T3SS is unknown. In this study, we showed that expression of Cpi-1/-1a T3SS is controlled by the master regulator CilA.

Comparative proteomic analysis of Salmonella enterica serovar Typhimurium ppGpp-deficient mutant to identify a novel virulence protein required for intracellular survival in macrophages.

Background: The global ppGpp-mediated stringent response in pathogenic bacteria plays an important role in the pathogenesis of bacterial infections. In Salmonella enterica serovar Typhimurium (S. Typhimurium), several genes, including virulence genes, are regulated by ppGpp when bacteria are under the stringent response.

Oral administration of heat-killed Lactobacillus plantarum strain b240 protected mice against Salmonella enterica Serovar Typhimurium.

The purpose of this study was to investigate the effects of heat-killed Lactobacillus plantarum strain b240 (b240) on systemic infection by Salmonella enterica serovar Typhimurium (S. Typhimurium) and to determine the mechanism by which b240 protects against infection. Mice were administered either b240 or saline orally for 3 weeks, and then inoculated with S.

Chromobacterium pathogenicity island 1 type III secretion system is a major virulence determinant for Chromobacterium violaceum-induced cell death in hepatocytes.

Chromobacterium violaceum is a Gram-negative bacterium that causes fatal septicaemia in humans and animals. C. violaceum ATCC 12472 possesses genes associated with two distinct type III secretion systems (T3SSs).

Phytohabitans suffuscus gen. nov., sp. nov., an actinomycete of the family Micromonosporaceae isolated from plant roots.

An actinomycete strain, K07-0523(T), was isolated from the roots of an orchid collected in Okinawa prefecture, Japan. 16S rRNA gene sequence analysis indicated that the new strain belonged to the family Micromonosporaceae and the similarity values between strain K07-0523(T) and the type species of 24 genera in the family Micromonosporaceae were 93.3-97.

Functional characterization of SsaE, a novel chaperone protein of the type III secretion system encoded by Salmonella pathogenicity island 2.

The type III secretion system (T3SS) encoded by Salmonella pathogenicity island 2 (SPI-2) is involved in systemic infection and intracellular replication of Salmonella enterica serovar Typhimurium. In this study, we investigated the function of SsaE, a small cytoplasmic protein encoded within the SPI-2 locus, which shows structural similarity to the T3SS class V chaperones. An S.

Genome-wide identification of novel genomic islands that contribute to Salmonella virulence in mouse systemic infection.

Salmonella pathogenicity islands are inserted into the genome by horizontal gene transfer and are required for expression of full virulence. Here, we performed tRNA scanning of the genome of Salmonella enterica serovar Typhimurium and compared it with that of nonpathogenic Escherichia coli in order to identify genomic islands that contribute to Salmonella virulence. Using deletion analysis, we identified four genomic islands that are required for virulence in the mouse infection model.

DsbA directs efficient expression of outer membrane secretin EscC of the enteropathogenic Escherichia coli type III secretion apparatus.

The formation of disulfide bond is essential for the folding, activity, and stability of many secreted proteins of Gram-negative bacteria. The disulfide oxidoreductase, DsbA, introduces disulfide bonds into exported proteins from the cytoplasm. In pathogenic bacteria, DsbA is required to process virulence determinants for their folding and assembly.

Identification of amino acid residues of Salmonella SlyA that are critical for transcriptional regulation.

The type III secretion system encoded by Salmonella pathogenicity island 2 (SPI-2) is essential for the intracellular survival and replication of Salmonella enterica. The expression of SPI-2 genes is dependent on a two-component regulatory system, SsrA (SpiR)/SsrB, encoded in the SPI-2 region. This paper shows that SlyA regulates transcription of the sensor kinase SsrA by binding to the ssrA promoter, indicating that SlyA is directly involved in the regulation of SPI-2 gene expression.

Probiotic Lactobacillus casei activates innate immunity via NF-kappaB and p38 MAP kinase signaling pathways.

Probiotic bacteria are microorganisms that benefit the host through improvement of the balance of intestinal microflora and possibly by augmentation of host defense systems. We examined the mechanisms for the up-regulation of innate immune responses by a probiotic Lactobacillus casei ATCC27139, in vivo. Using mouse models of systemic Listeria monocytogenes infection and MethA fibrosarcoma tumorigenesis in combination with BALB/c and SCID mice, we found that parenteral administration of L.

Identification of the outer-membrane protein PagC required for the serum resistance phenotype in Salmonella enterica serovar Choleraesuis.

Serum resistance is a crucial virulence factor for the development of systemic infections, including bacteraemia, by many pathogenic bacteria. Salmonella enterica serovar Choleraesuis is an important enteric pathogen that causes serious systemic infections in swine and humans. Here, it was found that, when introduced into Escherichia coli, a recombinant plasmid carrying the pagC gene from a plasmid-based genomic library of S.

Sequence analysis and characterization of sulfonamide resistance plasmid pRF-1 from Salmonella enterica serovar Choleraesuis.

The nucleotide sequence of a small plasmid, designated pRF-1, isolated from Salmonella enterica serovar Choleraesuis, was determined. We identified seven open reading frames (ORFs) encoded by 6066 nucleotides with a total G + C content of 53.6%.

Characterization of Salmonella pathogenicity island 1 type III secretion-dependent hemolytic activity in Salmonella enterica serovar Typhimurium.

A number of bacteria that are pathogenic for animals and plants possess a type III secretion system (TTSS) to translocate virulence-associated proteins into host cells. In several bacteria, it has been reported that the TTSS is correlated with an ability to cause contact-dependent hemolysis in vitro. Here, we showed that the Salmonella enterica serovar Typhimurium strain SL1344 exhibited Salmonella pathogenicity island 1 type III secretion-dependent, contact-mediated, hemolytic activity.

Two periplasmic disulfide oxidoreductases, DsbA and SrgA, target outer membrane protein SpiA, a component of the Salmonella pathogenicity island 2 type III secretion system.

The formation of disulfide is essential for the folding, activity, and stability of many proteins secreted by Gram-negative bacteria. The disulfide oxidoreductase, DsbA, introduces disulfide bonds into proteins exported from the cytoplasm to periplasm. In pathogenic bacteria, DsbA is required to process virulence determinants for their folding and assembly.

Intracellular expression of the Salmonella plasmid virulence protein, SpvB, causes apoptotic cell death in eukaryotic cells.

The spv genes carried on the Salmonella virulence plasmid are commonly associated with severe systemic infection in experimental animals. The SpvB virulence-associated protein has been shown to ADP-ribosylate actin, and this enzymatic activity is essential for virulence in mice. Here, we present evidence that intracellular expression of SpvB protein induces not only disruption of actin filaments but also apoptotic cell death in eukaryotic cells.

Protection against Shiga toxin 1 challenge by immunization of mice with purified mutant Shiga toxin 1.

Shiga toxin 1 (Stx1) of enterohemorrhagic Escherichia coli O157:H7 was cloned, and four mutant Stx1s were constructed by site-directed mutagenesis with PCR. The wild-type and mutant Stx1s with amino acid replacements at positions 167 and 170 of the A subunit were purified by one-step affinity chromatography with commercially available Globotriose Fractogel, and the mutant Stxs were used for the immunization of mice. The mutant toxins were nontoxic to Vero cells in vitro and to mice in vivo and induced the immunoglobulin G antibody against the wild-type Stx1, which neutralized the cytotoxicity of Stx1.

Extracellular secretion of the virulence plasmid-encoded ADP-ribosyltransferase SpvB in Salmonella.

Nontyphoid Salmonella enterica requires the plasmid-encoded spv genes to establish successful systemic infection in experimental animals. The SpvB virulence-associated protein has recently been shown to contain the ADP-ribosyltransferase domain. SpvB ADP-ribosilates actin and depolymerizes actin filaments when expressed in cultured epithelial cells.

Intracellular activity of fosfomycin against two distinct enteropathogenic bacteria, Salmonella enterica and Listeria monocytogenes, alive inside host cells.

We studied the effect of fosfomycin (FOM) on the intracellular growth of two different facultative intracellular bacteria, Salmonella enterica serovar Typhimurium and Listeria monocytogenes, in an enterocyte-like cell line, Caco-(2). These bacteria replicate in different compartments within the host cells; Salmonella serovar Typhimurium grow inside phagosomes, whereas L. monocytogenes escape the phagosomal environment and multiply in the cytosol of the host cells.

Association of a regulatory gene, slyA with a mouse virulence of Salmonella serovar Choleraesuis.

The influence of slyA gene, originally found in Salmonella serovar Typhimurium as a regulatory gene for the expression of virulence genes, on a mouse virulence of S. serovar Choleraesuis was investigated by using an slyA-defective mutant. The defective mutant was constructed by the insertion of a kanamycin-resistance gene (aph) into the cloned slyA gene, and the homologous recombination with the intact slyA gene on the chromosome.