Caractérisation des communautés microbiennes dans les lacs de la vallée de Stuckberry située dans l'Extrême-Arctique canadien

L'Arctique est confronté à une importante période de transition en raison du réchauffement atmosphérique accéléré. Pour les lacs qui dominent ces régions, il en découle une prolongation de la durée sans couvert de glace. Cette couche de glace est déterminante pour les écosystèmes aquatiques arctiques. Son absence augmente la fréquence des brassages de la colonne d'eau, l'exposition à la lumière, en plus d'altérer la stratification thermale. Les microorganismes, les acteurs principaux du réseau trophique et des cycles biogéochimiques des lacs arctiques, doivent donc s'adapter aux déséquilibres de leur environnement. Il s'avère crucial de mieux comprendre les impacts des changements climatiques sur les communautés microbiennes des lacs polaires afin d'anticiper leur portée à l'échelle mondiale. Aux premières loges des changements climatiques, les quatre lacs de la vallée de Stuckberry (île d'Ellesmere) représentent des laboratoires naturels pour l'étude de ces perturbations. Bien que proches en distance, ils diffèrent par leurs caractéristiques physicochimiques, morphologie et apports en eau et nutriments. Le séquençage par amplicon du gène codant pour l'ARNr 16S a été réalisé afin de comparer les communautés microbiennes intra et interlacs. Deux lacs profonds (>25 m) et majoritairement oxygénés ont montré des assemblages de communautés similaires, possiblement expliqué par la présence d'un ruisseau les reliant. Ces communautés étaient également très distinctes de celles des lacs peu profonds (25 m) and mostly oxygenated lakes showed highly similar community assemblages that were distinct from the two shallow lakes (<10 m) with anoxic bottom waters. Water exchange via a stream connecting these lakes most likely explains these similarities. Each lake, however, had its own unique vertically distributed assortment of microbes that was shaped by the limnological properties of its water column. One deep lake contained proportions of Cyanobacteria and Thaumarchaeota that distinguished it from the others. The shallow lakes had abundant communities of predatory bacteria, as well as microbes in their bottom waters contributing to the sulfur and methane cycles. This study establishes an important baseline characterization of microbial communities in lakes in a remote, extreme, and vulnerable region

Local habitat filtering shapes microbial community structure in four closely spaced lakes in the High Arctic

Arctic lakes are experiencing increasingly shorter periods of ice cover due to accelerated warming at northern high latitudes. Given the control of ice cover thickness and duration over many limnological processes, these changes will have pervasive effects. However, due to their remote and extreme locations even first-order data on lake ecology is lacking for many ecosystems. The aim of this study was to characterize and compare the microbial communities of four closely spaced lakes in Stuckberry Valley (northern Ellesmere Island, Canadian Arctic Archipelago), in the coastal margin zone of the Last Ice Area, that differed in their physicochemical, morphological and catchment characteristics. We performed high-throughput amplicon sequencing of the V4 16S rRNA gene to provide inter- and intra-lake comparisons. Two deep (>25 m) and mostly oxygenated lakes showed highly similar community assemblages that were distinct from those of two shallower lakes (<10 m) with anoxic bottom waters. Proteobacteria, Verrucomicrobia, and Planctomycetes were the major phyla present in the four water bodies. One deep lake contained elevated proportions of Cyanobacteria and Thaumarchaeota that distinguished it from the others, while the shallow lakes had abundant communities of predatory bacteria, as well as microbes in their bottom waters that contribute to sulfur and methane cycles. Despite their proximity, our data suggest that local habitat filtering is the primary determinant of microbial diversity in these systems. This study provides the first detailed examination of the microbial assemblages of the Stuckberry lakes system, resulting in new insights into the microbial ecology of the High Arctic

The Prostanoid 15-Deoxy-D 12,14 -Prostaglangin-J 2 Reduces Lung Inflammation and Protects Mice Against Lethal Influenza Infection

Background. Growing evidence indicates that influenza pathogenicity relates to altered immune responses and hypercytokinemia. Therefore, dampening the excessive inflammatory response induced after infection might reduce influenza morbidity and mortality. Methods. Considering this, we investigated the effect of the anti-inflammatory molecule 15-deoxy-D 12,14 -prostaglandin J 2 (15d-PGJ 2 ) in a mouse model of lethal influenza infection. Results. Administration of 15d-PGJ 2 on day 1 after infection, but not on day 0, protected 79% of mice against lethal influenza infection. In addition, this treatment considerably reduced the morbidity associated with severe influenza infection. Our results also showed that treatment with 15d-PGJ 2 decreased influenza-induced lung inflammation, as shown by the diminished gene expression of several proinflammatory cytokines and chemokines. Unexpectedly, 15d-PGJ 2 also markedly reduced the viral load in the lungs of infected mice. This could be attributed to maintained type I interferon gene expression levels after treatment. Interestingly, pretreatment of mice with a peroxisome proliferator-activated receptor gamma (PPARc) antagonist before 15d-PGJ 2 administration completely abrogated its protective effect against influenza infection. Conclusions. Our results demonstrate for the first time that treatment of mice with 15d-PGJ 2 reduces influenza morbidity and mortality through activation of the PPARc pathway. PPARc agonists could thus represent a potential therapeutic avenue for influenza infections

Coinfections and their molecular consequences in the porcine respiratory tract

Understudied, coinfections are more frequent in pig farms than single infections. In pigs, the term “Porcine Respiratory Disease Complex” (PRDC) is often used to describe coinfections involving viruses such as swine Influenza A Virus (swIAV), Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), and Porcine CircoVirus type 2 (PCV2) as well as bacteria like Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae and Bordetella bronchiseptica. The clinical outcome of the various coinfection or superinfection situations is usually assessed in the studies while in most of cases there is no clear elucidation of the fine mechanisms shaping the complex interactions occurring between microorganisms. In this comprehensive review, we aimed at identifying the studies dealing with coinfections or superinfections in the pig respiratory tract and at presenting the interactions between pathogens and, when possible, the mechanisms controlling them. Coinfections and superinfections involving viruses and bacteria were considered while research articles including protozoan and fungi were excluded. We discuss the main limitations complicating the interpretation of coinfection/superinfection studies, and the high potential perspectives in this fascinating research field, which is expecting to gain more and more interest in the next years for the obvious benefit of animal health

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

« L’accompagnabilité », une propriété des dispositifs de formation en alternance : Des manières d’accompagner et de se faire accompagner

Dans cette contribution, les auteurs étudient la propriété d’« accompagnabilité ». Ils la définissent comme la propension des dispositifs de formation en alternance à distribuer l’activité d’accompagnement, mais aussi comme celle des usagers à la redistribuer, à accompagner, à se faire accompagner, à s’accompagner soi-même.Pour étudier cette propriété dans sa diversité, ils ont d’abord identifié des logiques d’intervention différentes qu’ils nomment « spéculative », « normative » et « dialogique ». La logique d’intervention dialogique est plus spécifiquement étudiée, avec la collaboration de l’accompagnante qui a servi à la modéliser. Celle-ci revisite elle-même sa pratique avec l’outillage conceptuel et le matériau empirique issus de la recherche. La dernière partie du texte est conclusive. Elle porte sur les enseignements, les insuffisances et les perspectives de la démarche de recherche.In university Co-operative Education programs focussed on training professionals, writing professional memoires on the supervision activity is known to be conductive to student success. In this article, we will ask how to define and analyse supervision. Our approach is divided into four parts. After having clarified our understanding of Co-operative Education, we will describe some context elements that will be useful to readers, so they can assess the empirical foundation on which this paper is based. We will then explain how we developed three markers likely to characterize the supervisor’s professional memoire and how one supervisor mobilized and questioned these markers. We will then analyse the results before discussing them in the conclusion.En los dispositivos de formación universitaria en alternancia y con objetivos de profesionalización, la redaccion de los reportes profesionales asociados a la actividad de acompañamiento es supuestamente favorable para el éxito de los estudiantes. En esta contribución nos preguntamos ¿cómo definir y analizar la actividad de acompañamiento? La lógica expositiva que seguiremos se realizará en cuatro tiempos. Después de haber precisado nuestra concepción de la alternancia, indicaremos algunos elementos contextuales necesarios para el lector, para que puedan ponderar la base empírica sobre la que reposa esta contribución. Después explicaremos cómo elaboramos tres indicadores susceptibles de caracterizar la actividad de acompañamiento de una tesis profesional y cómo una acompañadora movilizó y cuestionó dichos indicadores. Finalmente, proponemos el análisis de los resultados obtenidos para en seguida discutirlos en la conclusión

Under-ice limnology of coastal valley lakes at the edge of the Arctic Ocean

The northern coast of Ellesmere Island in the Canadian High Arctic is undergoing amplified warming that parallels the rapid decline in Arctic Ocean sea ice extent, and many lakes in this region have already shown changes in response to warming. However, biogeochemical data from High Arctic freshwaters are limited, and mostly restricted to the short, ice-free period. We sampled four coastal lakes in Stuckberry Valley (82° 54’ N, 66° 56’ W) before the onset of spring melting in 2017, 2018 and 2019, to assess biogeochemical gradients in their water columns and characteristics of their surface sediments. Despite their proximity, there were large differences in limnological properties. The two shallower lakes closer to the ocean were oxygen deficient while the two deeper, more distant lakes were more oxygenated. There were pronounced vertical gradients in major ions, metals and nutrients that suggested large differences in the extent of anaerobic microbial processes among the lakes. Morphometry and dissolved oxygen were the overriding determinants of biogeochemical differences rather than position along this short oceaninland gradient. The diversity of limnological conditions, and the sensitivity of these characteristics to changes in ice cover, underlines the need for further study of under-ice processes in extreme northern lakes