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191.
Mamady Diabate Patrick Munro Elsa Garcia Arnaud Jacquel Gregory Michel Sandrine Obba Diogo Goncalves Carmelo Luci Sandrine Marchetti Dieter Demon Clara Degos Yassina Bechah Jean-Louis Mege Mohamed Lamkanfi Patrick Auberger Jean-Pierre Gorvel Lynda Maria Stuart Luce Landraud Emmanuel Lemichez Laurent Boyer 《PLoS pathogens》2015,11(3)
The detection of the activities of pathogen-encoded virulence factors by the innate immune system has emerged as a new paradigm of pathogen recognition. Much remains to be determined with regard to the molecular and cellular components contributing to this defense mechanism in mammals and importance during infection. Here, we reveal the central role of the IL-1β signaling axis and Gr1+ cells in controlling the Escherichia coli burden in the blood in response to the sensing of the Rho GTPase-activating toxin CNF1. Consistently, this innate immune response is abrogated in caspase-1/11-impaired mice or following the treatment of infected mice with an IL-1β antagonist. In vitro experiments further revealed the synergistic effects of CNF1 and LPS in promoting the maturation/secretion of IL-1β and establishing the roles of Rac, ASC and caspase-1 in this pathway. Furthermore, we found that the α-hemolysin toxin inhibits IL-1β secretion without affecting the recruitment of Gr1+ cells. Here, we report the first example of anti-virulence-triggered immunity counteracted by a pore-forming toxin during bacteremia. 相似文献
192.
Le Coadic M Simon M Marchetti A Ebert D Cosson P 《Applied and environmental microbiology》2012,78(2):593-595
We show that Daphnia magna can be used to assess acute virulence of pathogens relevant to human health, such as Pseudomonas aeruginosa or Photorhabdus asymbiotica. Analysis of bacterial mutants suggests that P. aeruginosa uses similar mechanisms to infect Daphnia and other hosts. 相似文献
193.
In essence, evolutionary processes occur gradually, while maintaining fitness throughout. Along this line, it has been proposed that the ability of a progenitor to promiscuously catalyze a low level of the evolving activity could facilitate the divergence of a new function by providing an immediate selective advantage. To directly establish a role for promiscuity in the divergence of natural enzymes, we attempted to trace the origins of a bacterial phosphotriesterase (PTE), an enzyme thought to have evolved for the purpose of degradation of a synthetic insecticide introduced in the 20th century. We surmised that PTE's promiscuous lactonase activity may be a vestige of its progenitor and tested homologues annotated as "putative PTEs" for lactonase and phosphotriesterase activity. We identified three genes that define a new group of microbial lactonases dubbed PTE-like lactonases (PLLs). These enzymes proficiently hydrolyze various lactones, and in particular quorum-sensing N-acyl homoserine lactones (AHLs), and exhibit much lower promiscuous phosphotriesterase activities. PLLs share key sequence and active site features with PTE and differ primarily by an insertion in one surface loop. Given their biochemical and biological function, PLLs are likely to have existed for many millions of years. PTE could have therefore evolved from a member of the PLL family while utilizing its latent promiscuous paraoxonase activity as an essential starting point. 相似文献
194.
Arie J. van Noordwijk Francisco Pulido Barbara Helm Timothy Coppack Julia Delingat Hugh Dingle Anders Hedenstr?m Henk van der Jeugd Chiara Marchetti Anna Nilsson Javier Pérez-Tris 《Journal of Ornithology》2006,147(2):221-233
Evolutionary change results from selection acting on genetic variation. For migration to be successful, many different aspects
of an animal’s physiology and behaviour need to function in a co-coordinated way. Changes in one migratory trait are therefore
likely to be accompanied by changes in other migratory and life-history traits. At present, we have some knowledge of the
pressures that operate at the various stages of migration, but we know very little about the extent of genetic variation in
various aspects of the migratory syndrome. As a consequence, our ability to predict which species is capable of what kind
of evolutionary change, and at which rate, is limited. Here, we review how our evolutionary understanding of migration may
benefit from taking a quantitative-genetic approach and present a framework for studying the causes of phenotypic variation.
We review past research, that has mainly studied single migratory traits in captive birds, and discuss how this work could
be extended to study genetic variation in the wild and to account for genetic correlations and correlated selection. In the
future, reaction-norm approaches may become very important, as they allow the study of genetic and environmental effects on
phenotypic expression within a single framework, as well as of their interactions. We advocate making more use of repeated
measurements on single individuals to study the causes of among-individual variation in the wild, as they are easier to obtain
than data on relatives and can provide valuable information for identifying and selecting traits. This approach will be particularly
informative if it involves systematic testing of individuals under different environmental conditions. We propose extending
this research agenda by using optimality models to predict levels of variation and covariation among traits and constraints.
This may help us to select traits in which we might expect genetic variation, and to identify the most informative environmental
axes. We also recommend an expansion of the passerine model, as this model does not apply to birds, like geese, where cultural
transmission of spatio-temporal information is an important determinant of migration patterns and their variation. 相似文献
195.
Claudio Pettinari Fabio Marchetti Alessandro Marinelli Anna Bellusci 《Inorganica chimica acta》2009,362(12):4593-3227
The sterically hindered tetrakis-(3-(p-tolylpyrazolyl)borate [pz0Tpp-Tol] has been prepared and its reaction with CuX2.nH2O (X = Cl or acetate (OAc), M(NO3)2.6H2O (M = Ni, or Co) and MCl2 (M = Zn or Cd) has been investigated. [M(pz0Tpp-Tol)X(Hpzp-Tol)] (M = Cu, X = Cl or OAc; M = Ni or Co, X = NO3) and [M(pz0Tpp-Tol)Cl(Hpzp-Tol)2-n(H2O)n] have been synthesised and their spectroscopic properties described, the five-coordinated Cu species being also structurally characterized. The methyl groups in the para-tolyl fragments of the ligand strongly influences the stoichiometry and structure of the metal complexes. 相似文献
196.
The Notch ankyrin repeat domain contains seven ankyrin sequence repeats, six of which adopt very similar structures. To determine if folding proceeds along parallel pathways and the order in which repeats become structured during folding, we examined the effect of analogous destabilizing Ala-->Gly substitutions in each repeat on folding kinetics. We find that folding proceeds to an on-pathway kinetic intermediate through a transition state ensemble containing structure in repeats three through five. Repeats two, six, and seven remain largely unstructured in this intermediate, becoming structured in a second kinetic step that leads to the native state. These data suggest that the Notch ankyrin domain folds according to a discrete kinetic pathway despite structural redundancy in the native state and highlight the importance of sequence-specific interactions in controlling pathway selection. This centralized pathway roughly corresponds to a low energy channel through the experimentally determined energy landscape. 相似文献
197.
TiCl3(thf)3 reacts with ACl (A = NBu4, PPN; PPN = Ph3PNPPh3) in dichloromethane solution, affording the compounds A[TiCl4(thf)2] (A = NBu4, 1; A = PPN, 2). Compound 1, dissolved in CH2Cl2, exhibits thermochromic behaviour which has been the subject of variable-temperature UV-Vis investigations. 相似文献
198.
199.
200.
Benghezal M Fauvarque MO Tournebize R Froquet R Marchetti A Bergeret E Lardy B Klein G Sansonetti P Charette SJ Cosson P 《Cellular microbiology》2006,8(1):139-148
The amoeba Dictyostelium discoideum shares many traits with mammalian macrophages, in particular the ability to phagocytose and kill bacteria. In response, pathogenic bacteria use conserved mechanisms to fight amoebae and mammalian phagocytes. Here we developed an assay using Dictyostelium to monitor phagocyte-bacteria interactions. Genetic analysis revealed that the virulence of Klebsiella pneumoniae measured by this test is very similar to that observed in a mouse pneumonia model. Using this assay, two new host resistance genes (PHG1 and KIL1) were identified and shown to be involved in intracellular killing of K. pneumoniae by phagocytes. Phg1 is a member of the 9TM family of proteins, and Kil1 is a sulphotransferase. The loss of PHG1 resulted in Dictyostelium susceptibility to a small subset of bacterial species including K. pneumoniae. Remarkably, Drosophila mutants deficient for PHG1 also exhibited a specific susceptibility to K. pneumoniae infections. Systematic analysis of several additional Dictyostelium mutants created a two-dimensional virulence array, where the complex interactions between host and bacteria are visualized. 相似文献