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The endopolysaccharide accumulated by Thermococcus hydrothermalis was extracted and purified from a 4 h culture. It presented an “amylopectin-like” structure with an average chain length
of 14 and a ramification degree of 7.5%. The glucosyltransferase was isolated, partially purified and characterized. The molecular
mass was 42 kDa by SDS PAGE and 85 ± 5 kDa by gel filtration. This enzyme was able to use both Uridine-5′-DiPhosphoGlucose
(UDPG) and Adenosine-5′-DiPhosphoGlucose (ADPG) as substrates. Optimal pH and temperature for the enzyme were 5.5 and 80°C,
respectively. In the presence of 3.2 mM ADPG, the half life of the protein was 6 min at 110°C. The apparent K
m
value with the two substrates was 0.9 mM, but the V
max
was 9.7 fold higher for ADPG. A branching activity was also detected at high temperature, up to 80°C by different methods:
phosphorylase stimulation, iodine, and branching linkage assays. 相似文献
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Adaptive processes of Staphylococcus aureus isolates during the progression from acute to chronic bone and joint infections in patients
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Sophie Trouillet‐Assant Patrícia Martins‐Simões Luiz Gonzaga Jason Tasse Florent Valour Jean‐Philippe Rasigade François Vandenesch Rafael Lucas Muniz Guedes Ana Tereza Ribeiro de Vasconcelos Jocelyne Caillon Sebastien Lustig Tristan Ferry Frédéric Laurent 《Cellular microbiology》2016,18(10):1405-1414
Staphylococcus aureus bone and joint infection (BJI) is associated with significant rates of chronicity and relapse. In this study, we investigated how S. aureus is able to adapt to the human environment by comparing isolates from single patients with persisting or relapsing BJIs that were recovered during the initial and recurrent BJI episodes. In vitro and in vivo assays and whole‐genome sequencing analyses revealed that the recurrent isolates induced a reduced inflammatory response, formed more biofilms, persisted longer in the intracellular compartments of host bone cells, were less cytotoxic and induced less mortality in a mouse infection model compared with the initial isolates despite the lack of significant changes at the genomic level. These findings suggest that S. aureus BJI chronicization is associated with an in vivo bacterial phenotypical adaptation that leads to decreased virulence and host immune escape, which is linked to increased intraosteoblastic persistence and biofilm formation. 相似文献
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Gregory Lacraz Volatiana Rakotoarivelo Sebastien M. Labbé Mathieu Vernier Christophe Noll Marian Mayhue Jana Stankova Adel Schwertani Guillaume Grenier André Carpentier Denis Richard Gerardo Ferbeyre Julie Fradette Marek Rola-Pleszczynski Alfredo Menendez Marie-France Langlois Subburaj Ilangumaran Sheela Ramanathan 《PloS one》2016,11(9)
ObjectiveIL-15 is an inflammatory cytokine secreted by many cell types. IL-15 is also produced during physical exercise by skeletal muscle and has been reported to reduce weight gain in mice. Contrarily, our findings on IL-15 knockout (KO) mice indicate that IL-15 promotes obesity. The aim of this study is to investigate the mechanisms underlying the pro-obesity role of IL-15 in adipose tissues.MethodsControl and IL-15 KO mice were maintained on high fat diet (HFD) or normal control diet. After 16 weeks, body weight, adipose tissue and skeletal mass, serum lipid levels and gene/protein expression in the adipose tissues were evaluated. The effect of IL-15 on thermogenesis and oxygen consumption was also studied in primary cultures of adipocytes differentiated from mouse preadipocyte and human stem cells.ResultsOur results show that IL-15 deficiency prevents diet-induced weight gain and accumulation of lipids in visceral and subcutaneous white and brown adipose tissues. Gene expression analysis also revealed elevated expression of genes associated with adaptive thermogenesis in the brown and subcutaneous adipose tissues of IL-15 KO mice. Accordingly, oxygen consumption was increased in the brown adipocytes from IL-15 KO mice. In addition, IL-15 KO mice showed decreased expression of pro-inflammatory mediators in their adipose tissues.ConclusionsAbsence of IL-15 results in decreased accumulation of fat in the white adipose tissues and increased lipid utilization via adaptive thermogenesis. IL-15 also promotes inflammation in adipose tissues that could sustain chronic inflammation leading to obesity-associated metabolic syndrome. 相似文献
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Sebastien A. Burel Christopher E. Hart Patrick Cauntay Jill Hsiao Todd Machemer Melanie Katz Andy Watt Huynh-hoa Bui Husam Younis Mahyar Sabripour Susan M. Freier Gene Hung Amy Dan T.P. Prakash Punit P. Seth Eric E. Swayze C. Frank Bennett Stanley T. Crooke Scott P. Henry 《Nucleic acids research》2016,44(5):2093-2109
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Vascular plant‐mediated controls on atmospheric carbon assimilation and peat carbon decomposition under climate change
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Konstantin Gavazov Remy Albrecht Alexandre Buttler Ellen Dorrepaal Mark H. Garnett Sebastien Gogo Frank Hagedorn Robert T. E. Mills Bjorn J. M. Robroek Luca Bragazza 《Global Change Biology》2018,24(9):3911-3921
Climate change can alter peatland plant community composition by promoting the growth of vascular plants. How such vegetation change affects peatland carbon dynamics remains, however, unclear. In order to assess the effect of vegetation change on carbon uptake and release, we performed a vascular plant‐removal experiment in two Sphagnum‐dominated peatlands that represent contrasting stages of natural vegetation succession along a climatic gradient. Periodic measurements of net ecosystem CO2 exchange revealed that vascular plants play a crucial role in assuring the potential for net carbon uptake, particularly with a warmer climate. The presence of vascular plants, however, also increased ecosystem respiration, and by using the seasonal variation of respired CO2 radiocarbon (bomb‐14C) signature we demonstrate an enhanced heterotrophic decomposition of peat carbon due to rhizosphere priming. The observed rhizosphere priming of peat carbon decomposition was matched by more advanced humification of dissolved organic matter, which remained apparent beyond the plant growing season. Our results underline the relevance of rhizosphere priming in peatlands, especially when assessing the future carbon sink function of peatlands undergoing a shift in vegetation community composition in association with climate change. 相似文献
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