Microbial diversity and community structure across environmental gradients in Bransfield Strait, Western Antarctic Peninsula

© The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Microbiology 5 (2014): 647, doi:10.3389/fmicb.2014.00647.The Southern Ocean is currently subject to intense investigations, mainly related to its importance for global biogeochemical cycles and its alarming rate of warming in response to climate change. Microbes play an essential role in the functioning of this ecosystem and are the main drivers of the biogeochemical cycling of elements. Yet, the diversity and abundance of microorganisms in this system remain poorly studied, in particular with regards to changes along environmental gradients. Here, we used amplicon sequencing of 16S rRNA gene tags using primers covering both Bacteria and Archaea to assess the composition and diversity of the microbial communities from four sampling depths (surface, the maximum and minimum of the oxygen concentration, and near the seafloor) at 10 oceanographic stations located in Bransfield Strait [northwest of the Antarctic Peninsula (AP)] and near the sea ice edge (north of the AP). Samples collected near the seafloor and at the oxygen minimum exhibited a higher diversity than those from the surface and oxygen maximum for both bacterial and archaeal communities. The main taxonomic groups identified below 100 m were Thaumarchaeota, Euryarchaeota and Proteobacteria (Gamma-, Delta-, Beta-, and Alphaproteobacteria), whereas in the mixed layer above 100 m Bacteroidetes and Proteobacteria (mainly Alpha- and Gammaproteobacteria) were found to be dominant. A combination of environmental factors seems to influence the microbial community composition. Our results help to understand how the dynamic seascape of the Southern Ocean shapes the microbial community composition and set a baseline for upcoming studies to evaluate the response of this ecosystem to future changes.This work was supported by the Brazilian National Counsel of Technological and Scientific Development (Polar Canion CNPq 556848/2009-8, ProOasis CNPq 565040/2010-3, Interbiota CNPq 407889/2013-2 and INCT-MAR-COI). Alex Enrich-Prast received a CNPq Productivity fellowship. Camila N. Signori was supported by a WHOI Mary Sears Visitor Award (for the microbial community analyses) and by the Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES) for the “Doctorate Sandwich” scholarship (n. 18835/12-0)

Temporal changes in the expression and distribution of adhesion molecules during liver development and regeneration

We have compared by immunocytochemistry and immunoblotting the expression and distribution of adhesion molecules participating in cell-matrix and cell-cell interactions during embryonic development and regeneration of rat liver. Fibronectin and the fibronectin receptor, integrin alpha 5 beta 1, were distributed pericellularly and expressed at a steady level during development from the 16th day of gestation and in neonate and adult liver. AGp110, a nonintegrin fibronectin receptor was first detected on the 17th day of gestation in a similar, nonpolarized distribution on parenchymal cell surfaces. At that stage of development haemopoiesis is at a peak in rat liver and fibronectin and receptors alpha 5 beta 1 and AGp110 were prominent on the surface of blood cell precursors. During the last 2 d of gestation (20th and 21st day) hepatocytes assembled around lumina. AGp110 was initially depolarized on the surface of these acinar cells but then confined to the lumen and to newly-formed bile canaliculi. At birth, a marked increase occurred in the canalicular expression of AGp110 and in the branching of the canalicular network. Simultaneously, there was enhanced expression of ZO-1, a protein component of tight junctions. On the second day postpartum, presence of AGp110 and of protein constituents of desmosomes and intermediate junctions, DGI and E-cadherin, respectively, was notably enhanced in cellular fractions insoluble in nonionic detergents, presumably signifying linkage of AGp110 with the cytoskeleton and assembly of desmosomal and intermediate junctions. During liver regeneration after partial hepatectomy, AGp110 remained confined to apical surfaces, indicating a preservation of basic polarity in parenchymal cells. A decrease in the extent and continuity of the canalicular network occurred in proliferating parenchyma, starting 24 h after resection in areas close to the terminal afferent blood supply of portal veins and spreading to the rest of the liver within the next 24 h. Distinct acinar structures, similar to the ones in prenatal liver, appeared at 72 h after hepatectomy. Restoration of the normal branching of the biliary tree commenced at 72 h. At 7 d postoperatively acinar formation declined and one-cell-thick hepatic plates, as in normal liver, were observed

Reversal of murine alcoholic steatohepatitis by pepducin-based functional blockade of interleukin-8 receptors.

OBJECTIVE: Alcoholic steatohepatitis is a life-threatening condition with short-term mortality up to 40%. It features hepatic neutrophil infiltration and blood neutrophilia, and may evolve from ethanol-induced breakdown of the enteric barrier and consequent bacteraemia. Signalling through CXCR1/2 G-protein-coupled-receptors (GPCRs), the interleukin (IL)-8 receptors, is critical for the recruitment and activation of neutrophils. We have developed short lipopeptides (pepducins), which inhibit post-ligand GPCR activation precisely targeting individual GPCRs. DESIGN: Experimental alcoholic liver disease was induced by administering alcohol and a Lieber-DeCarli high-fat diet. CXCR1/2 GPCRs were blocked via pepducins either from onset of the experiment or after disease was fully established. Hepatic inflammatory infiltration, hepatocyte lipid accumulation and overall survival were assessed as primary outcome parameters. Neutrophil activation was assessed by myeloperoxidase activity and liver cell damage by aspartate aminotransferase and alanine aminotransferase plasma levels. Chemotaxis assays were performed to identify chemoattractant signals derived from alcohol-exposed hepatocytes. RESULTS: Here, we show that experimental alcoholic liver disease is driven by CXCR1/2-dependent activation of neutrophils. CXCR1/2-specific pepducins not only protected mice from liver inflammation, weight loss and mortality associated with experimental alcoholic liver disease, but therapeutic administration cured disease and prevented further mortality in fully established disease. Hepatic neutrophil infiltration and triglyceride accumulation was abrogated by CXCR1/2 blockade. Moreover, CXCL-1 plasma levels were decreased with the pepducin therapy as was the transcription of hepatic IL-1β mRNA. CONCLUSIONS: We propose that high circulating IL-8 in human alcoholic hepatitis may cause pathogenic overzealous neutrophil activation, and therapeutic blockade via pepducins merits clinical study.Wellcome Trust Career Re-entry Fellowship (103077/Z/13/Z) to NCK, Christian Doppler Research Society to HT and European Research Council (FP7/2007- 2013) to AKThis is the final version of the article. It first appeared from the BMJ Group via http://dx.doi.org/10.1136/gutjnl-2015-31034

Simultaneous Continuation of Infinitely Many Sinks Near a Quadratic Homoclinic Tangency

We prove that the $C^3$ diffeomorphisms on surfaces, exhibiting infinitely many sinksnear the generic unfolding of a quadratic homoclinic tangency of a dissipative saddle, can be perturbed along an infinite dimensional manifold of $C^3$ diffeomorphisms such that infinitely many sinks persist simultaneously. On the other hand, if they are perturbed along one-parameter families that unfold generically the quadratic tangencies, then at most a finite number of those sinks have continuation

GD3 synthase overexpression sensitizes hepatocarcinoma cells to hypoxia and reduces tumor growth by suppressing the cSrc/NF-κB survival pathway

This is an open-access article distributed under the terms of the Creative Commons Attribution License.[Background]: Hypoxia-mediated HIF-1a stabilization and NF-kB activation play a key role in carcinogenesis by fostering cancer cell survival, angiogenesis and tumor invasion. Gangliosides are integral components of biological membranes with an increasingly recognized role as signaling intermediates. In particular, ganglioside GD3 has been characterized as a proapoptotic lipid effector by promoting cell death signaling and suppression of survival pathways. Thus, our aim was to analyze the role of GD3 in hypoxia susceptibility of epatocarcinoma cells and in vivo tumor growth.[Methodology/Principal Findings]: We generated and characterized a human hepatocarcinoma cell line stably expressing GD3 synthase (Hep3B-GD3), which catalyzes the synthesis of GD3 from GM3. Despite increased GD3 levels (2–3 fold), no significant changes in cell morphology or growth were observed in Hep3B-GD3 cells compared to wild type Hep3B cells under normoxia. However, exposure of Hep3B-GD3 cells to hypoxia (2% O2) enhanced reactive oxygen species (ROS) generation, resulting in decreased cell survival, with similar findings observed in Hep3B cells exposed to increasing doses of exogenous GD3. In addition, hypoxia-induced c-Src phosphorylation at tyrosine residues, NF-kB activation and subsequent expression of Mn-SOD were observed in Hep3B cells but not in Hep3B-GD3 cells. Moreover, MnTBAP, an antioxidant with predominant SOD mimetic activity, reduced ROS generation, protecting Hep3B-GD3 cells from hypoxia-induced death. Finally, lower tumor growth, higher cell death and reduced Mn-SOD expression were observed in Hep3B-GD3 compared to Hep3B tumor xenografts.[Conclusion]: These findings underscore a role for GD3 in hypoxia susceptibility by disabling the c-Src/NF-kB survival pathway resulting in lower Mn-SOD expression, which may be of relevance in hepatocellular carcinoma therapy.Grant support: CIBEREHD and grants FIS06/0395, FIS07/1039, SAF2006-06789 and SAF2008-02199 by Instituto de Salud Carlos III and Ministry of Science and Innovation from Spain, and from the Research Center for Liver and Pancreatic Diseases, P50-AA-11999 funded by the US National Institute on Alcohol Abuse and Alcoholism.Peer reviewe

Up-regulation of the anti-inflammatory adipokine adiponectin in acute liver failure in mice

BACKGROUND/AIMS: Recent reports suggest that the adipose tissue and adipokines are potent modulators of inflammation. However, there is only scarce knowledge on the functional role and regulation of endogenous adiponectin in non-fat tissues such as the liver under conditions of acute inflammation. METHODS: In the present study, we investigated adiponectin expression in healthy murine liver tissue and under inflammatory conditions in vivo. RESULTS: Adiponectin mRNA was readily detectable in healthy liver tissue and further increased in ConA-mediated acute liver failure. Adiponectin protein expression was mainly found in hepatic endothelial cells. In vitro adiponectin mRNA expression was detectable in several cell types, including primary hepatic sinusoidal endothelial cells, stellate cells, and macrophages. Mice pretreated with adiponectin before ConA administration developed reduced hepatic injury as shown by decreased release of transaminases and reduced hepatocellular apoptotis. Of note, TNF-alpha levels were not affected by adiponectin, whereas IL-10 production was increased. Neutralisation of IL-10 diminished the protective effect of adiponectin. CONCLUSIONS: Adiponectin expression is up-regulated in ConA-mediated acute liver failure. Therefore, adiponectin might play a role in the control and limitation of inflammation in the liver. Moreover, our data suggest a role for IL-10 in adiponectin-mediated hepatoprotection

Large emissions from floodplain trees close the Amazon methane budget

Wetlands are the largest global source of atmospheric methane (CH4), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain, the largest natural geographic source of CH4 in the tropics, consistently underestimate the atmospheric burden of CH4 determined via remote sensing and inversion modelling, pointing to a major gap in our understanding of the contribution of these ecosystems to CH4 emissions. Here we report CH4 fluxes from the stems of 2,357 individual Amazonian floodplain trees from 13 locations across the central Amazon basin. We find that escape of soil gas through wetland trees is the dominant source of regional CH4 emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests6 and tropical peat swamp forests, representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (δ13C) of −66.2 ± 6.4 per mil, consistent with a soil biogenic origin. We estimate that floodplain trees emit 15.1 ± 1.8 to 21.2 ± 2.5 teragrams of CH4 a year, in addition to the 20.5 ± 5.3 teragrams a year emitted regionally from other sources. Furthermore, we provide a ‘top-down’ regional estimate of CH4 emissions of 42.7 ± 5.6 teragrams of CH4 a year for the Amazon basin, based on regular vertical lower-troposphere CH4 profiles covering the period 2010–2013. We find close agreement between our ‘top-down’ and combined ‘bottom-up’ estimates, indicating that large CH4 emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH4 budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH4 emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH4 source when trees are combined with other emission sources

The MAL protein is crucial for proper membrane condensation at the ciliary base, which is required for primary cilium elongation

The base of the primary cilium contains a zone of condensed membranes whose importance is not known. Here, we have studied the involvement of MAL, a tetraspanning protein that exclusively partitions into condensed membrane fractions, in the condensation of membranes at the ciliary base and investigated the importance of these membranes in primary cilium formation. We show that MAL accumulates at the ciliary base of epithelial MDCK cells. Knockdown of MAL expression resulted in a drastic reduction in the condensation of membranes at the ciliary base, the percentage of ciliated cells and the length of the cilia, but did not affect the docking of the centrosome to the plasma membrane or produce missorting of proteins to the pericentriolar zone or to the membrane of the remaining cilia. Rab8 (for which there are two isoforms, Rab8A and Rab8b), IFT88 and IFT20, which are important components of the machinery of ciliary growth, were recruited normally to the ciliary base of MAL-knockdown cells but were unable to elongate the primary cilium correctly. MAL, therefore, is crucial for the proper condensation of membranes at the ciliary base, which is required for efficient primary cilium extensionThis work was supported by the Ministerio de Economıa y Competitividad, Spain [grant numbers BFU2012-32532 and CONSOLIDER COAT CSD2009-00016 to M. A.A.]. G.A. was supported by the Amarouto Program for senior researchers from the Comunidad Autónoma de Madri

Latin America's Nitrogen Challenge

Latin America (LA) has many social indicators similar to those of highly developed economies but most frequently falls midway between least developed countries and industrialized regions. To move forward, LA must address uncontrolled urbanization, agricultural production, social inequity, and destruction of natural resources. We discuss these interrelated challenges in terms of human impact on the nitrogen (N) cycle. Human activity has caused unprecedented changes to the global N cycle; in the past century; total global fixation of reactive N (Nr) has at least doubled (1). Excess Nr leaked into the environment negatively affects soils, atmosphere, and water resources in temperate zones (1). In addition to N excess from human impact, mining of natural soil N creates N deficits in some regions (2, 3).Fil: Austin, Amy Theresa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Bustamante, M. M. C.. Universidade Do Brasilia; BrasilFil: Nardoto, G. B.. Universidade Do Brasilia; BrasilFil: Mitre, S. K.. Universidade Do Brasilia; BrasilFil: Pérez, T.. Instituto Venezolano de Investigaciones Cientificas; VenezuelaFil: Ometto, J. P. H. B.. Centro de Previsao de Tempo e Estudos Climaticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Ascarrunz, N. L.. Instituto Boliviano de Investigación Forestal; BoliviaFil: Forti, M. C.. Centro de Previsao de Tempo e Estudos Climaticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Longo, K.. Centro de Previsao de Tempo e Estudos Climaticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Gavito, M. E.. Universidad Nacional Autónoma de México; MéxicoFil: Enrich Prast, A.. Universidade Federal do Rio de Janeiro; BrasilFil: Martinelli, L. A.. Universidade de Sao Paulo; Brasi

Cholesterol Overload: Contact Sites to the Rescue!

Delivery of low-density lipoprotein-derived cholesterol to the endoplasmic reticulum (ER) is essential for cholesterol homeostasis, yet the mechanism of this transport has largely remained elusive. Two recent reports shed some light on this process, uncovering a role for Niemann Pick type-C1 protein (NPC1) in the formation of membrane contact sites (MCS) between late endosomes (LE)/lysosomes (Lys) and the ER. Both studies identified a loss of MCS in cells lacking functional NPC1, where cholesterol accumulates in late endocytic organelles. Remarkably, and taking different approaches, both studies have made a striking observation that expansion of LE/Lys-ER MCS can rescue the cholesterol accumulation phenotype in NPC1 mutant or deficient cells. In both cases, the cholesterol was shown to be transported to the ER, demonstrating the importance of ER-LE/Lys contact sites in the direct transport of low-density lipoprotein-derived cholesterol to the ER