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  • 1
    Language: English
    In: Resonance, Nov, 2013, Vol.18(11), p.963(3)
    Description: Byline: Dipshikha Chakravortty (1) Author Affiliation: (1) Department of MCBL, Indian Institute of Science, Bangalore, 560 012, India Article History: Registration Date: 29/11/2013 Online Date: 30/11/2013
    Keywords: Education ; Science Education ; Science, General ; Education ; Sciences (General);
    ISSN: 0971-8044
    E-ISSN: 0973712X
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  • 2
    Language: English
    In: 2012, Vol.7(9), p.e45417
    Description: Feeding Caenorhabditis elegans with Salmonella enterica serovar Typhimurium significantly shortens the lifespan of the nematode. S . Typhimurium-infected C. elegans , stained with 2′,7′-dichlorodihydrofluorescein diacetate which fluoresces upon exposure to reactive oxygen species, revealed intestinal luminal staining that along with the time of infection progressed to a strong staining in the hypodermal tissues of the nematode. Still, we could not detect invasion beyond the nematode's intestinal epithelium at any stage of the infection. A similar dispersion of oxidative response was also noted in nematodes infected with S . Dublin, but not with non-pathogenic Escherichia coli or the defined pathogen Burkholderia thailandensis . Addition of catalase or the reductant ascorbic acid significantly restored the lifespan of S . Typhimurium-infected nematodes. Mutational inactivation of the bacterial thioredoxin 1 resulted in total ablation of the hypodermal oxidative response to infection, and in a strong attenuation of virulence. Virulence of the thioredoxin 1 mutant was restored by trans -complementation with redox-active variants of thioredoxin 1 or, surprisingly, by exposing the thioredoxin 1 mutant to sublethal concentrations of the disulphide catalyst copper chloride prior to infection. In summary, our observations define a new aspect in virulence of S. enterica that apparently does not involve the classical invasive or intracellular phenotype of the pathogen, but that depends on the ability to provoke overwhelming systemic oxidative stress in the host through the redox activity of bacterial thioredoxin 1.
    Keywords: Research Article ; Biology ; Medicine ; Microbiology ; Cell Biology ; Oncology
    E-ISSN: 1932-6203
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  • 3
    Language: English
    In: PLoS ONE, 2011, Vol.6(11), p.e27535
    Description: Bordetella pertussis filamentous hemagglutinin (FHA) is a surface-associated and secreted protein that serves as a crucial adherence factor, and displays immunomodulatory activity in human peripheral blood mononuclear cells (PBMCs). In order to appreciate more fully the role of secreted FHA in pathogenesis, we analyzed FHA-induced changes in genome-wide transcript abundance in human PBMCs. Among the 683 known unique genes with greater than 3-fold change in transcript abundance following FHA treatment, 125 (18.3%) were identified as interferon (IFN)-regulated. Among the latter group were genes encoding several members of the IFN type I response, as well as 3 key components of the ISGylation pathway. Using real-time RT-PCR, we confirmed FHA-associated increases in transcript abundance for the genes encoding ubiquitin-like protein, ISG15, and its specific protease USP18. Western-blot analysis demonstrated the presence of both, free ISG15 and several ISGylated conjugates in FHA-stimulated PBMC lysates, but not in unstimulated cells. Intracellular FACS analysis provided evidence that monocytes and a natural killer-enriched cell population were the primary producers of ISG15 in PBMCs after FHA stimulation. Our data reveal previously-unrecognized effects of B. pertussis FHA on host IFN and ISGylation responses, and suggest previously-unsuspected mechanisms by which FHA may alter the outcome of the host-pathogen interaction.
    Keywords: Research Article ; Biology ; Medicine ; Genetics And Genomics ; Immunology ; Infectious Diseases ; Microbiology
    E-ISSN: 1932-6203
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  • 4
    Language: English
    In: PLoS ONE, 2011, Vol.6(10), p.e26930
    Description: Many Gram-negative pathogens possess virulence-related type III secretion systems. Salmonella enterica uses two of these systems, encoded on the pathogenicity islands SPI-1 and SPI-2, respectively, to translocate more than 30 effector proteins into eukaryotic host cells. SteA is one of the few effectors that can be translocated by both systems. We investigated the conditions affecting the synthesis of this effector, its secretion to culture media and its translocation into host cells. Whereas steA was expressed under a wide range of conditions, some factors, including low and high osmolarity, and presence of butyrate, decreased expression. SteA was efficiently secreted to the culture media under both SPI-1 and SPI-2 inducing conditions. The kinetics of translocation into murine macrophages and human epithelial cells was studied using fusions with the 3xFLAG tag, and fusions with CyaA from Bordetella pertussis . Translocation into macrophages under non-invasive conditions was mainly dependent on the SPI-2-encoded type III secretion system but some participation of the SPI-1 system was also detected 6 hours post-infection. Interestingly, both type III secretion systems had a relevant role in the translocation of SteA into epithelial cells. Finally, a deletion approach allowed the identification of the N-terminal signal necessary for translocation of this effector. The amino acid residues 1–10 were sufficient to direct translocation into host cells through both type III secretion systems. Our results provide new examples of functional overlapping between the two type III secretion systems of Salmonella .
    Keywords: Research Article ; Biology ; Medicine ; Genetics And Genomics ; Infectious Diseases ; Microbiology ; Biochemistry
    E-ISSN: 1932-6203
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  • 5
    Language: English
    In: PLoS ONE, 2012, Vol.7(3), p.e33220
    Description: The molecular mechanisms of virulence of the gastrointestinal pathogen Salmonella enterica are commonly studied using cell culture models of infection. In this work, we performed a direct comparison of the interaction of S. enterica serovar Typhimurium ( S. Typhimurium) with the non-polarized epithelial cell line HeLa, the polarized cell lines CaCo2, T84 and MDCK, and macrophage-like RAW264.7 cells. The ability of S. Typhimurium wild-type and previously characterized auxotrophic mutant strains to enter host cells, survive and proliferate within mammalian cells and deploy the Salmonella Pathogenicity Island 2-encoded type III secretion system (SPI2-T3SS) was quantified. We found that the entry of S. Typhimurium into polarized cells was much more efficient than entry into non-polarized cells or phagocytic uptake. While SPI2-T3SS dependent intracellular proliferation was observed in HeLa and RAW cells, the intracellular replication in polarized cells was highly restricted and not affected by defective SPI2-T3SS. The contribution of aromatic amino acid metabolism and purine biosynthesis to intracellular proliferation was distinct in the various cell lines investigated. These observations indicate that the virulence phenotypes of S. Typhimurium are significantly affected by the cell culture model applied.
    Keywords: Research Article ; Biology ; Microbiology ; Cell Biology
    E-ISSN: 1932-6203
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  • 6
    Language: English
    In: 2013, Vol.8(9), p.e77031
    Description: We have examined the antimicrobial activity of C-terminal analogs of human β-defensins HBD-1and-3 wherein lysines have been selectively replaced by L- and D-arginines and L-isoleucine substituted with its D-enantiomer. The analogs exhibited antibacterial and antifungal activities. Physiological concentration of NaCl did not attenuate the activity of the peptides against Gram-negative bacteria considerably, while some attenuation of activity was observed against S. aureus . Variable attenuation of activity was observed in the presence of Ca 2+ and Mg 2+ . Introduction of D-amino acids abrogated the need for a disulfide bridge for exhibiting activity. Confocal images of carboxyfluorescein (CF) labeled peptides indicated initial localization on the membrane and subsequent translocation into the cell. Analogs corresponding to cationic rich segments of human defensins substituted with L- and D-arginine, could be attractive candidates for development as future therapeutic drugs.
    Keywords: Research Article
    E-ISSN: 1932-6203
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  • 7
    Language: English
    In: Resonance, 2014, Vol.19(11), pp.1005-1016
    Description: Biofilm is a lifestyle exhibited by bacteria. This is an intricate process that involves cell—Ccell communication which leads to the regulation of certain genes. This affects the laying down of the extracellular matrices which form the substratum for the biofilm. In this review, we have discussed in detail about the mechanism behind biofilm formation and the physiological importance of biofilm lifestyle for the bacteri
    Keywords: Biofilm ; bacteria ; bacterial community
    ISSN: 0971-8044
    E-ISSN: 0973-712X
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  • 8
    Language: English
    In: Analytical biochemistry, 2011, Vol.419(2), pp.292-301
    Description: Shock waves are one of the most competent mechanisms of energy dissipation observed in nature. We have developed a novel device to generate controlled micro-shock waves using an explosive-coated polymer tube. In this study, we harnessed these controlled micro-shock waves to develop a unique bacterial transformation method. The conditions were optimized for the maximum transformation efficiency in Escherichia coli. The maximum transformation efficiency was obtained when we used a 30cm length polymer tube, 100μm thick metal foil, 200mM CaCl₂, 1ng/μl plasmid DNA concentration, and 1×10⁹ cell density. The highest transformation efficiency achieved (1×10⁻⁵ transformants/cell) was at least 10 times greater than the previously reported ultrasound-mediated transformation (1×10⁻⁶ transformants/cell). This method was also successfully employed for the efficient and reproducible transformation of Pseudomonas aeruginosa and Salmonellatyphimurium. This novel method of transformation was shown to be as efficient as electroporation with the added advantage of better recovery of cells, reduced cost (40 times cheaper than a commercial electroporator), and growth phase independent transformation. ; p. 292-301.
    Keywords: Calcium Chloride ; Foil ; Cost Effectiveness ; Escherichia Coli ; Plasmids ; Pseudomonas Aeruginosa ; Polymers ; Energy ; Electroporation
    ISSN: 0003-2697
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 9
    Language: English
    In: PLoS ONE, 2012, Vol.7(4), p.e35880
    Description: It is well known that some strains of lactic acid bacteria (LAB) can induce IL-12 which plays an important role in modulating immune responses. However, the mechanisms by which LAB induce IL-12 production remain unclear. Here, we examine the role of toll-like receptors (TLR's) and reactive oxygen species (ROS) in IL-12 production by LAB stimulated peritoneal macrophages. Our results indicate that a TLR is not necessary for IL-12 induction by LAB, whilst the universal adaptor protein, MyD88, is essential. Specific strains of LAB induced ROS that correlated with both the frequency of phagocytosis and IL-12 production. Reduction in IL-12 production by NADPH oxidase inhibitors or ROS scavengers demonstrates the crucial role of ROS in IL-12 induction. Interestingly, deficiency of TLR2, 4, 9 or MyD88 did not affect the phagocytosis of LAB strain KW3110, a potent IL-12 inducer, and ROS production was significantly reduced only in MyD88 deficient macrophages. These results suggest the existence of TLR-MyD88 independent LAB recognition and MyD88 related ROS induction mechanisms. We show here the importance of ROS for IL-12 induction and provide new insights into IL-12 induction by LAB.
    Keywords: Research Article ; Biology ; Immunology ; Microbiology ; Physiology ; Biotechnology
    E-ISSN: 1932-6203
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  • 10
    Language: English
    In: PLoS ONE, 2012, Vol.7(7), p.e40841
    Description: Simple cost-effective bacterins are the earliest and most successfully used commercial vaccines in fish. In particular, those prepared from Yersinia ruckeri have proven effective at controlling Enteric Red Mouth Disease (ERM) and yersiniosis in rainbow trout and Atlantic salmon, respectively. However, the emergence of outbreaks of ERM caused by atypical biotypes of Y. ruckeri and reports of vaccine failure resulting in mass mortality of hatchery Atlantic salmon has reinvigorated interest in vaccines against fish bacterial diseases. Therefore the objective of this study was to identify surrogates of protection against yersiniosis using cDNA microarray to characterise the response of host genes in the gills of unvaccinated and vaccinated Atlantic salmon challenged with Y. ruckeri . Differentially expressed genes were identified using two-way ANOVA and restricted to those with 〉2.5-fold change at P 〈0.05. Using cDNA microarray we identified the expression of 6 genes in response to infection and 4 genes associated with the protective host response to yersiniosis. Analysis by real-time PCR confirmed that three immunologically relevant genes, namely a cathelicidin (47-fold) and a C-type lectin (19-fold) increased in response to yersiniosis. Including collagenase (17-fold increase), an important tissue remodelling and repair enzyme, these genes represent 3 of 6 non-protective and/or pathological responses to yersiniosis. Genes associated with the protective host response included an immunoglobulin gene and a selenoprotein that showed significant fold changes (15-fold increases each), highlighting the importance of antibody-mediated protection against yersiniosis. These findings provide much needed knowledge of the host-pathogen interaction in response to bacterial infection and immunisation in fish. Significantly, we identified a transcriptional biosignature consisting of predominantly immune-relevant genes (14 up and 3 down-regulated) in the gills of Atlantic salmon after immersion vaccination and before bacterial challenge. This biosignature may be used as a surrogate of protection and therefore as a predictor of vaccine success against yersiniosis.
    Keywords: Research Article ; Agriculture ; Biology ; Veterinary Science ; Immunology ; Microbiology ; Marine And Aquatic Sciences ; Computational Biology
    E-ISSN: 1932-6203
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