Retracing Storage Polysaccharide Evolution in Stramenopila

Eukaryotes most often synthesize storage polysaccharides in the cytosol or vacuoles in the form of either alpha (glycogen/starch)- or beta-glucosidic (chrysolaminarins and paramylon) linked glucan polymers. In both cases, the glucose can be packed either in water-soluble (glycogen and chrysolaminarins) or solid crystalline (starch and paramylon) forms with different impacts, respectively, on the osmotic pressure, the glucose accessibility, and the amounts stored. Glycogen or starch accumulation appears universal in all free-living unikonts (metazoa, fungi, amoebozoa, etc.), as well as Archaeplastida and alveolata, while other lineages offer a more complex picture featuring both alpha- and beta-glucan accumulators. We now infer the distribution of these polymers in stramenopiles through the bioinformatic detection of their suspected metabolic pathways. Detailed phylogenetic analysis of key enzymes of these pathways correlated to the phylogeny of Stramenopila enables us to retrace the evolution of storage polysaccharide metabolism in this diverse group of organisms. The possible ancestral nature of glycogen metabolism in eukaryotes and the underlying source of its replacement by beta-glucans are discussed

La conservation inattendue du métabolisme du glycogène chez les Chlamydiae souligne une fonction essentielle des polysaccharides de réserve dans leur cycle de développement

For almost a century, the Chlamydiae phylum contained only the Chlamydiaceae family, which encompasses etiological agents of severe infectious diseases in humans. Today, fifteen families have enriched this phylum in which the so-called Chlamydia-like bacteria or environmental Chlamydiae are distributed. The hallmark of all Chlamydiae is a huge genome reduction leading to an obligate intracellular lifestyle and a biphasic lifecycle including a highly metabolically active intracellular form (i.e reticulate bodies) and an extracellular (i.e. elementary body) form. While glycogen metabolism loss is viewed as an adaptation to the intracellular lifestyle, all Chlamydiae are singularly distinguished from other intracellular pathogens by the maintenance of the GlgC-pathway, which is the one described in Escherichia coli. Some environmental Chlamydiae, however seemed to deviate from this rule. Indeed, the glgC gene, encoding ADP-glucose pyrophosphorylase activity is missing in the genome of Estrella lausannensis (family Criblamydiaceae) and Waddlia chondrophila (family Waddliaceae). The lack of this key enzyme suggested that chlamydial strains are therefore defective in glycogen biosynthesis. However, electron microscopic observation of thin sections of E. lausannensis and W. chondrophila elemental bodies stained with PATAg (specific glycogen staining) clearly refuted this presumption. In order to explain this unexpected result, 220 genomes reflecting chlamydial diversity were examined for their gene content of the glycogen biosynthesis pathway reported in bacteria: the GlgC pathway and the GlgE pathway, recently evidenced in Mycobacterium tuberculosis. We thus identified in E. lausannensis and W. chondrophila but also in phylogenetically related Chlamydiae, the GlgE pathway, which is based on four enzymatic reactions enabling the synthesis of glycogen from trehalose. The enzymatic characterizations of TreS-Mak; a bifunctional enzyme that converts trehalose to maltose-1-phosphate and GlgE; a maltosyltransferase activity responsible for the synthesis of α-1,4 glucan chains, confirmed that this pathway is functional in these two environmental Chlamydiae. In addition, we show that, like glycogen synthase (GlgA) of the GlgC pathway, GlgE activity is capable of initiating de novo glycogen synthesis without the aid of a glucan primer. Finally, preliminary studies suggest that acetylation of lysine residues, a post-translational modification involved in the regulation of many enzymes of the carbon metabolism in bacteria, may activate GlgE activity. Altogether this study demonstrates that glycogen metabolism is conserved in all Chlamydiae, without exception, despite the genome reduction process, thus underlining an essential function, underestimated to date, of this storage polysaccharide. We propose that the degradation of glycogen may provide the energy required to sustain basal metabolic functions, which are essential for the survival and virulence of extracellular forms, i.e. elementary bodies.Pendant près d’un siècle, le phylum Chlamydiae n’a contenu que la famille des Chlamydiaceae, qui regroupe les agents étiologiques de sévères maladies infectieuses chez l'Homme. Aujourd'hui, quinze familles enrichissent ce phylum où se répartissent les bactéries dites Chlamydia-like ou Chlamydiae environnementales. Les Chlamydiae, bactéries intracellulaires obligatoires, se caractérisent par une réduction importante de leur génome et un cycle de vie biphasique comprenant une forme intracellulaire métaboliquement très active (le corps réticulé) et une forme extracellulaire dormante et infectieuse (le corps élémentaire). Alors que la perte du métabolisme du glycogène, est décrite comme une adaptation à la vie intracellulaire, les Chlamydiae se distinguent singulièrement des autres pathogènes intracellulaires par un maintien de la voie GlgC qui est identique à celle décrite chez Escherichia coli. Cependant des Chlamydiae environnementales semblaient déroger à cette règle. En effet, le gène glgC, codant l’activité ADP-glucose pyrophosphorylase, est absent dans les génomes d’Estrella lausannensis (famille Criblamydiaceae) et de Waddlia chondrophila (famille Waddliaceae). L’absence de cette enzyme clef laissait supposer que les souches soient, par conséquent, défectueuses dans la biosynthèse du glycogène. L’observation au microscope électronique de fines sections colorées au PATAg (coloration spécifique du glycogène) de corps élémentaires d’E. lausannensis et de W. chondrophila ont toutefois clairement réfuté cette idée reçue. Afin d’expliquer ce résultat inattendu, 220 génomes représentant la diversité des Chlamydiae ont été scrutés pour leur contenu en gènes des voies de biosynthèse du glycogène documentés chez les bactéries : la voie GlgC et la voie GlgE, récemment décrite chez Mycobacterium tuberculosis. Nous avons ainsi identifié chez E. lausannensis et W. chondrophila mais aussi chez des Chlamydiae phylogénétiquement apparentées, la voie GlgE qui repose sur quatre réactions enzymatiques permettant la synthèse du glycogène à partir du tréhalose. Une caractérisation biochimique de l’activité TreS-Mak; une enzyme bifonctionnelle qui convertit le tréhalose en maltose-1-phosphate et de l’activité GlgE; une activité maltosyltransférase responsable de la synthèse de chaînes d’α-1,4 glucanes, ont confirmé que la voie GlgE était bien fonctionnelle chez ces deux Chlamydiae environnementales. En outre, nous avons montré que, à l’instar de la glycogène synthase (GlgA) de la voie GlgC, l’activité GlgE est capable d'initier la synthèse du glycogène de novo sans l’aide d'une amorce glucanique. Enfin, des études préliminaires suggèrent que l’acétylation des résidus lysines, une modification post-traductionnelle qui intervient dans la régulation de nombreuses enzymes impliquées dans le métabolisme carboné chez les bactéries, activerait l’activité GlgE. L'ensemble de cette étude démontre que le métabolisme du glycogène est conservé chez toutes les Chlamydiae, sans exception, et ce malgré le processus de réduction du génome, soulignant ainsi une fonction essentielle, sous-estimée à ce jour, de ce polysaccharide de réserve. Nous proposons que le catabolisme du glycogène fournisse l’énergie nécessaire au maintien des fonctions métaboliques basales, qui sont indispensables à la survie et à la virulence des formes extracellulaires c’est-à-dire des corps élémentaires

Substitution of nucleotide-sugar by trehalose-dependent glycogen synthesis pathways in Chlamydiales underlines an unusual requirement for storage polysaccharides within obligate intracellular bacteria

International audienceAll obligate intracellular pathogens or symbionts of eukaryotes lack glycogen metabolism. Most members of the Chlamydiales order are exceptions to this rule as they contain the classical GlgA-GlgC-dependent pathway of glycogen metabolism that relies on the ADP-Glucose substrate. We surveyed the diversity of Chlamydiales and found glycogen metabolism to be universally present with the important exception of Criblamydiaceae and Waddliaceae families that had been previously reported to lack an active pathway. However, we now find elements of the more recently described GlgE maltose-1-P-dependent pathway in several protist-infecting Chlamydiales. In the case of Waddliaceae and Criblamydiaceae, the substitution of the classical pathway by this recently proposed GlgE pathway was essentially complete as evidenced by the loss of both GlgA and GlgC. Biochemical analysis of recombinant proteins expressed from Waddlia chondrophila and Estrella lausannensis established that both enzymes do polymerize glycogen from trehalose through the production of maltose-1-P by TreS-Mak and its incorporation into glycogen’s outer chains by GlgE. Unlike Mycobacteriaceae where GlgE-dependent polymerization is produced from both bacterial ADP-Glc and trehalose, glycogen synthesis seems to be entirely dependent on host supplied UDP-Glc and Glucose-6-P or on host supplied trehalose and maltooligosaccharides. These results are discussed in the light of a possible effector nature of these enzymes, of the chlamydial host specificity and of a possible function of glycogen in extracellular survival and infectivity of the chlamydial elementary bodies. They underline that contrarily to all other obligate intracellular bacteria, glycogen metabolism is indeed central to chlamydial replication and maintenance

CommunitySolidServer/CommunitySolidServer: v7.0.3

<p>Fixed issues:</p> <ul> <li>Require Append instead of Write permissions when creating a new resource with PUT https://github.com/CommunitySolidServer/CommunitySolidServer/pull/1825</li> <li>Fixed an issue when linking external WebIDs to your account https://github.com/CommunitySolidServer/CommunitySolidServer/pull/1827</li> <li>Better defaults when starting the server through code https://github.com/CommunitySolidServer/CommunitySolidServer/pull/1811</li> </ul&gt

Hemodynamic management of critically ill burn patients: an international survey.

n/aFunding Agencies|European Society of Intensive Care Medicine</p

Ventilation practices in burn patients - an international prospective observational cohort study

Background: It is unknown whether lung-protective ventilation is applied in burn patients and whether they benefit from it. This study aimed to determine ventilation practices in burn intensive care units (ICUs) and investigate the association between lung-protective ventilation and the number of ventilator-free days and alive at day 28 (VFD-28). Methods: This is an international prospective observational cohort study including adult burn patients requiring mechanical ventilation. Low tidal volume (V T) was defined as V T ≤ 8 mL/kg predicted body weight (PBW). Levels of positive end-expiratory pressure (PEEP) and maximum airway pressures were collected. The association between V T and VFD-28 was analyzed using a competing risk model. Ventilation settings were presented for all patients, focusing on the first day of ventilation. We also compared ventilation settings between patients with and without inhalation trauma. Results: A total of 160 patients from 28 ICUs in 16 countries were included. Low V T was used in 74% of patients, median V T size was 7.3 [interquartile range (IQR) 6.2-8.3] mL/kg PBW and did not differ between patients with and without inhalation trauma (p = 0.58). Median VFD-28 was 17 (IQR 0-26), without a difference between ventilation with low or high V T (p = 0.98). All patients were ventilated with PEEP levels ≥5 cmH2O; 80% of patients had maximum airway pressures <30 cmH2O. Conclusion: In this international cohort study we found that lung-protective ventilation is used in the majority of burn patients, irrespective of the presence of inhalation trauma. Use of low V T was not associated with a reduction in VFD-28. Trial registration: Clinicaltrials.gov NCT02312869. Date of registration: 9 December 2014

Ventilation practices in burn patients-an international prospective observational cohort study

Background: It is unknown whether lung-protective ventilation is applied in burn patients and whether they benefit from it. This study aimed to determine ventilation practices in burn intensive care units (ICUs) and investigate the association between lung-protective ventilation and the number of ventilator-free days and alive at day 28 (VFD-28). Methods: This is an international prospective observational cohort study including adult burn patients requiring mechanical ventilation. Low tidal volume (V-T) was defined as V-T &lt;= 8 mL/kg predicted body weight (PBW). Levels of positive end-expiratory pressure (PEEP) and maximum airway pressures were collected. The association between V-T and VFD-28 was analyzed using a competing risk model. Ventilation settings were presented for all patients, focusing on the first day of ventilation. We also compared ventilation settings between patients with and without inhalation trauma. Results: A total of 160 patients from 28 ICUs in 16 countries were included. Low V-T was used in 74% of patients, median V-T size was 7.3 [interquartile range (IQR) 6.2-8.3] mL/kg PBW and did not differ between patients with and without inhalation trauma (p= 0.58). Median VFD-28 was 17 (IQR 0-26), without a difference between ventilation with low or high V-T (p= 0.98). All patients were ventilated with PEEP levels &gt;= 5 cmH(2)O; 80% of patients had maximum airway pressures &lt;30 cmH(2)O. Conclusion: In this international cohort study we found that lung-protective ventilation is used in the majority of burn patients, irrespective of the presence of inhalation trauma. Use of low V-T was not associated with a reduction in VFD-28