The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Stefan Becker - One of the best experts on this subject based on the ideXlab platform.
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the common structural architecture of Shigella flexneri and salmonella typhimurium type three secretion needles
PLOS Pathogens, 2013Co-Authors: Jean Philippe Demers, Nikolaos G Sgourakis, Rashmi Gupta, Antoine Loquet, Karin Giller, Dietmar Riedel, Britta Laube, Michael Kolbe, David Baker, Stefan BeckerAbstract:The Type Three Secretion System (T3SS), or injectisome, is a macromolecular infection machinery present in many pathogenic Gram-negative bacteria. It consists of a basal body, anchored in both bacterial membranes, and a hollow needle through which effector proteins are delivered into the target host cell. Two different architectures of the T3SS needle have been previously proposed. First, an atomic model of the Salmonella typhimurium needle was generated from solid-state NMR data. The needle subunit protein, PrgI, comprises a rigid-extended N-terminal segment and a helix-loop-helix motif with the N-terminus located on the outside face of the needle. Second, a model of the Shigella flexneri needle was generated from a high-resolution 7.7-A cryo-electron microscopy density map. The subunit protein, MxiH, contains an N-terminal α-helix, a loop, another α-helix, a 14-residue-long β-hairpin (Q51–Q64) and a C-terminal α-helix, with the N-terminus facing inward to the lumen of the needle. In the current study, we carried out solid-state NMR measurements of wild-type Shigella flexneri needles polymerized in vitro and identified the following secondary structure elements for MxiH: a rigid-extended N-terminal segment (S2-T11), an α-helix (L12-A38), a loop (E39-P44) and a C-terminal α-helix (Q45-R83). Using immunogold labeling in vitro and in vivo on functional needles, we located the N-terminus of MxiH subunits on the exterior of the assembly, consistent with evolutionary sequence conservation patterns and mutagenesis data. We generated a homology model of Shigella flexneri needles compatible with both experimental data: the MxiH solid-state NMR chemical shifts and the state-of-the-art cryoEM density map. These results corroborate the solid-state NMR structure previously solved for Salmonella typhimurium PrgI needles and establish that Shigella flexneri and Salmonella typhimurium subunit proteins adopt a conserved structure and orientation in their assembled state. Our study reveals a common structural architecture of T3SS needles, essential to understand T3SS-mediated infection and develop treatments.
P. J. Sansonetti - One of the best experts on this subject based on the ideXlab platform.
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In vivo apoptosis in Shigella flexneri infections.
Infection and immunity, 1996Co-Authors: Andarturo Zychlinsky, Kavitha Thirumalai, J Arondel, J R Cantey, Antonios O. Aliprantis, P. J. SansonettiAbstract:Shigella flexneri, an etiological agent of bacillary dysentery, causes apoptosis in vitro. Here we show that it also induces apoptosis in vivo. We were able to quantify the number of apoptotic cells in rabbit Peyer's patches infected with S. flexneri by detecting cells with fragmented DNA. Infection with virulent S. flexneri results in massive numbers of apoptotic cells within the lymphoid follicles. In contrast, neither an avirulent strain nor an avirulent strain capable of colonizing Peyer's patches increases the background level of apoptotic cells. Macrophages, T cells, and B cells are shown to undergo apoptosis in vivo. These results indicate that apoptosis may play a crucial role in the pathogenesis of shigellosis.
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Die Invasion von Epithelzellen durch Shigella flexneri
Ökosystem Darm VI, 1994Co-Authors: T. Adam, Monique Arpin, M.-c. Prévost, P. Gounon, P. J. SansonettiAbstract:Shigella flexneri ist das am besten untersuchte atiologische Agens der bakteriellen Ruhr, einer Erkrankung, an der jahrlich weltweit mindestens 500 000 Menschen sterben [11]. Wahrend die Shigellose in gemasigten Klimazonen sporadisch oder in epidemischer Form auftritt, ist die von S. flexneri verursachte Erkrankung in subtropischen und tropischen Regionen endemisch.
Wu Rong-rong - One of the best experts on this subject based on the ideXlab platform.
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BIOLOGICAL AND MOLECULAR ANALYSIS ON Shigella flexneri 4C SUBSEROTYPE ISOLATED IN SHENZHEN
Modern Preventive Medicine, 2011Co-Authors: Wu Rong-rongAbstract:[Objective]To investigate the biological and molecular characteristics of Shigella flexneri 4c subtype isolated for the first time in Shenzhen.[Methods]Biochemical characterization,serosubtype,Congo red binding ability and antimicrobial susceptibility,plasmid profile,virulence gene detection were applied to analyse the isolates.[Results]Isolates of Shigella flexneri 4c subtype all fermented glucose and mannitol,and were all Shigella flexneri type IV,group 7 serotype.Congo red binding ability tests all got positive results.The isolates were resistant to Ampicillin,tetracycline,Trimethoprim and Amoxicillin,while sensitive to Amikacin,Ciprofloxacin,Gentamicin,Cefotaxime,Cefalotin and Norfloxacin.All of the strains' plasmid profile are similar,but different from F4a and F4b.IpaH and set1 gene were presented in all strains,while ial and sen gene were only presented in 23.5% strains.[Conclusion]This isolates' biochemical characterization and serotype are similar to those reported.Congo red binding positive ability reflects the bacteria have some virulence.It's better to use more sensitive antibiotic drugs than those resistant drugs like Ampicillin in the clinical treatment on diseases caused by this kind of Shigella flexneri subtype.The strains all come from the same source.Ial and sen virulence gene are absent in most of the strains.
Jean Philippe Demers - One of the best experts on this subject based on the ideXlab platform.
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the common structural architecture of Shigella flexneri and salmonella typhimurium type three secretion needles
PLOS Pathogens, 2013Co-Authors: Jean Philippe Demers, Nikolaos G Sgourakis, Rashmi Gupta, Antoine Loquet, Karin Giller, Dietmar Riedel, Britta Laube, Michael Kolbe, David Baker, Stefan BeckerAbstract:The Type Three Secretion System (T3SS), or injectisome, is a macromolecular infection machinery present in many pathogenic Gram-negative bacteria. It consists of a basal body, anchored in both bacterial membranes, and a hollow needle through which effector proteins are delivered into the target host cell. Two different architectures of the T3SS needle have been previously proposed. First, an atomic model of the Salmonella typhimurium needle was generated from solid-state NMR data. The needle subunit protein, PrgI, comprises a rigid-extended N-terminal segment and a helix-loop-helix motif with the N-terminus located on the outside face of the needle. Second, a model of the Shigella flexneri needle was generated from a high-resolution 7.7-A cryo-electron microscopy density map. The subunit protein, MxiH, contains an N-terminal α-helix, a loop, another α-helix, a 14-residue-long β-hairpin (Q51–Q64) and a C-terminal α-helix, with the N-terminus facing inward to the lumen of the needle. In the current study, we carried out solid-state NMR measurements of wild-type Shigella flexneri needles polymerized in vitro and identified the following secondary structure elements for MxiH: a rigid-extended N-terminal segment (S2-T11), an α-helix (L12-A38), a loop (E39-P44) and a C-terminal α-helix (Q45-R83). Using immunogold labeling in vitro and in vivo on functional needles, we located the N-terminus of MxiH subunits on the exterior of the assembly, consistent with evolutionary sequence conservation patterns and mutagenesis data. We generated a homology model of Shigella flexneri needles compatible with both experimental data: the MxiH solid-state NMR chemical shifts and the state-of-the-art cryoEM density map. These results corroborate the solid-state NMR structure previously solved for Salmonella typhimurium PrgI needles and establish that Shigella flexneri and Salmonella typhimurium subunit proteins adopt a conserved structure and orientation in their assembled state. Our study reveals a common structural architecture of T3SS needles, essential to understand T3SS-mediated infection and develop treatments.
David A. Sack - One of the best experts on this subject based on the ideXlab platform.
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Altering trends in the dominance of Shigella flexneri serotypes and emergence of serologically atypical S. flexneri strains in Dhaka, Bangladesh.
Journal of clinical microbiology, 2001Co-Authors: Kaisar A. Talukder, Dilip K. Dutta, Ashrafus Safa, M. Ansaruzzaman, Ferdaus Hassan, Khorshed Alam, K. M. N. Islam, Nils Carlin, G. B. Nair, David A. SackAbstract:Of 469 recently isolated Shigella flexneri strains, 452 agglutinated with Shigella flexneri-specific monoclonal antibodies. Of these, 396 could be assigned to 10 of the currently recognized 15 serotypes, with S. flexneri 2b dominating (23.2%). Of the 56 untypeable strains which showed invasive properties, 17 were serologically atypical and the remaining 39 belonged to a new serotype.