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1.
The difficulty in predicting the consequences of interactions between different cytokine networks has increased with the expansion
of the T helper (Th) cell universe and the discovery of numerous B lymphocyte-derived cytokines. Consequently, it is now difficult
to conceptualize a straightforward view of the contribution of these disturbances to the pathogenesis of primary Sj?gren's
syndrome (SS). Th1 cells, which produce interferon-γ and IL-2, and Th17 cells, which make IL-17 and TNF-α, have been cast
in the leading roles of the play. However, the complex role of T-cell subsets in SS is accentuated by the reciprocal effects
of Th17 cells and regulatory T cells found in salivary glands of SS patients. Furthermore, B lymphocyte polarization into
type-1 B effector (Be1) and Be2 cells and B-cell modulating factors of the TNF family, most notably the B-cell-activating
factor (BAFF), and their prominent role in SS are additional complicating factors. Whereas Th17 cells orchestrate autoreactive
germinal centers, local BAFF would repress the generation of Th17 cells. Such new insights into interconnected cytokines in
primary SS may lead to new treatments for these patients. 相似文献
2.
Positive selection procedure for entrapment of insertion sequence elements in gram-negative bacteria. 总被引:72,自引:45,他引:27
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We constructed the broad-host-range plasmid pUCD800 containing the sacB gene of Bacillus subtilis for use in the positive selection and isolation of insertion sequence (IS) elements in gram-negative bacteria. Cells containing pUCD800 do not grow on medium containing 5% sucrose unless the sacB gene is inactivated. By using pUCD800, we isolated a 1.4-kilobase putative IS element from Agrobacterium tumefaciens NT1RE by selection for growth on sucrose medium. This putative IS element appears to be unique to Agrobacterium strains. 相似文献
3.
Cloning structural gene sacB, which codes for exoenzyme levansucrase of Bacillus subtilis: expression of the gene in Escherichia coli. 总被引:17,自引:10,他引:7
A clone bearing the structural gene sacB, coding for the exoenzyme levansucrase, was isolated from a library of Bacillus subtilis DNA that was cloned in phage lambda charon 4A on the basis of the transforming activity of the chimeric DNA. This lambda clone also was found to contain the sacR and smo loci. Subcloning the sacB-sacR region in plasmid pBR325 resulted in a clone which directed levansucrase synthesis in Escherichia coli. The nucleotide sequence coding for the secreted protein was localized on the physical map of the cloned DNA. 相似文献
4.
Zbigniew Lazar Tristan Rossignol Jonathan Verbeke Anne-Marie Crutz-Le Coq Jean-Marc Nicaud Małgorzata Robak 《Journal of industrial microbiology & biotechnology》2013,40(11):1273-1283
Yarrowia lipolytica requires the expression of a heterologous invertase to grow on a sucrose-based substrate. This work reports the construction of an optimized invertase expression cassette composed of Saccharomyces cerevisiae Suc2p secretion signal sequence followed by the SUC2 sequence and under the control of the strong Y. lipolytica pTEF promoter. This new construction allows a fast and optimal cleavage of sucrose into glucose and fructose and allows cells to reach the maximum growth rate. Contrary to pre-existing constructions, the expression of SUC2 is not sensitive to medium composition in this context. The strain JMY2593, expressing this new cassette with an optimized secretion signal sequence and a strong promoter, produces 4,519 U/l of extracellular invertase in bioreactor experiments compared to 597 U/l in a strain expressing the former invertase construction. The expression of this cassette strongly improved production of invertase and is suitable for simultaneously high production level of citric acid from sucrose-based media. 相似文献
5.
Mathieu Coulis Stephan Hättenschwiler Sylvain Coq Jean-François David 《Ecosystems》2016,19(6):1104-1115
In many terrestrial ecosystems, large amounts of leaf litter are consumed by macroarthropods. Most of it is deposited as faeces that are easily transferred into deeper soil layers. However, the decomposition of this large pool of organic matter remains poorly studied. We addressed the question of how leaf litter transformation into macroarthropod faeces, and their burial in the soil, affect organic matter decomposition in a Mediterranean dry shrubland. We compared mass loss of intact leaf litter of two dominant shrub species (Quercus coccifera, Cistus albidus) with that of leaf litter-specific faeces from the abundant millipede Ommatoiulus sabulosus. Leaf litter and faeces were exposed in the field for 1 year, either on the soil surface or buried at 5 cm soil depth. Chemical and physical quality of faeces differed strongly from that of leaf litter, but distinctively between the two shrub species. On the soil surface, faeces decomposed faster than intact leaf litter in Quercus, but at similar rates in Cistus. When buried in the soil, faeces and leaf litter decomposed at similar rates in either species, but significantly faster compared to the soil surface, most likely because of higher moisture within the soil enhancing microbial activity. The combined effects of leaf litter transformation into faeces and their subsequent burial in the topsoil led to a 1.5-fold increase in the annual mass loss. These direct and indirect macroarthropod effects on ecosystem-scale decomposition are likely more widespread than currently acknowledged, and may play a particularly important role in drought-influenced ecosystems. 相似文献
6.
Aspartoacylase catalyzes the deacetylation of N-acetylaspartic acid (NAA) in the brain to produce acetate and L-aspartate. An aspartoacylase deficiency, with concomitant accumulation of NAA, is responsible for Canavan disease, a lethal autosomal recessive disorder. To examine the mechanism of this enzyme the genes encoding murine and human aspartoacylase were cloned and expressed in Escherichia coli. A significant portion of the enzyme is expressed as soluble protein, with the remainder found as inclusion bodies. A convenient enzyme-coupled continuous spectrophotometric assay has been developed for measuring aspartoacylase activity. Kinetic parameters were determined with the human enzyme for NAA and for selected N-acyl analogs that demonstrate relaxed substrate specificity with regard to the nature of the acyl group. The clinically relevant E285A mutant reveals an altered enzyme with poor stability and barely detectable activity, while a more conservative E285D substitution leads to only fivefold lower activity than native aspartoacylase. 相似文献
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9.
Pilar Sanchez-Vizuete Dominique Le Coq Arnaud Bridier Jean-Marie Herry Stéphane Aymerich Romain Briandet 《Applied and environmental microbiology》2015,81(1):109-118
In most habitats, microbial life is organized in biofilms, three-dimensional edifices sustained by extracellular polymeric substances that enable bacteria to resist harsh and changing environments. Under multispecies conditions, bacteria can benefit from the polymers produced by other species (“public goods”), thus improving their survival under toxic conditions. A recent study showed that a Bacillus subtilis hospital isolate (NDmed) was able to protect Staphylococcus aureus from biocide action in multispecies biofilms. In this work, we identified ypqP, a gene whose product is required in NDmed for thick-biofilm formation on submerged surfaces and for resistance to two biocides widely used in hospitals. NDmed and S. aureus formed mixed biofilms, and both their spatial arrangement and pathogen protection were mediated by YpqP. Functional ypqP is present in other natural B. subtilis biofilm-forming isolates. However, the gene is disrupted by the SPβ prophage in the weak submerged-biofilm-forming strains NCIB3610 and 168, which are both less resistant than NDmed to the biocides tested. Furthermore, in a 168 laboratory strain cured of the SPβ prophage, the reestablishment of a functional ypqP gene led to increased thickness and resistance to biocides of the associated biofilms. We therefore propose that YpqP is a new and important determinant of B. subtilis surface biofilm architecture, protection against exposure to toxic compounds, and social behavior in bacterial communities. 相似文献
10.