Bacteria of debris-covered glaciers
Ontology highlight
ABSTRACT:
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| ERR117407_1.fastq.gz | Fastqsanger.gz | |||
| ERR117407_2.fastq.gz | Fastqsanger.gz | |||
| ERR117408_1.fastq.gz | Fastqsanger.gz | |||
| ERR117408_2.fastq.gz | Fastqsanger.gz | |||
| ERR117409_1.fastq.gz | Fastqsanger.gz |
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Project description:The human placenta is covered by a single multinucleated fetal cell, the syncytiotrophoblast, which is bathed in maternal blood. During all pregnancies, membrane enclosed extracellular vesicles derived from the syncytiotrophoblast are extruded into the maternal blood.The large size of these extracellular vesicles (diameter larger than 10µm) is referred to as trophoblastic debris in this study. We have shown in the past that endothleial cells are involved in clearence of this trophoblastic debris and induction of immune tolerence by trophoblastic debris.This study aimed to characterise the transcriptional changes that occur in human vascular endothelial cells following exposure to trophoblastic debris from normal first trimester placentae. Microarrays were used to probe transcriptomic changes 2 and 21 hours after exposure of endothelial cells (Human microvascular endothelial cell line,HMEC-1) to trophoblastic debris from normal first trimester placentae
2016-08-21 | GSE69996 | GEO
Project description:The degree to which debris-covered glaciers record past environmental conditions is debated. Here we describe a novel palaeoclimate archive derived from the surface morphology and internal debris within cold-based debris-covered glaciers in Antarctica. Results show that subtle changes in mass balance impart major changes in the concentration of englacial debris and corresponding surface topography, and that over the past ?220?ka, at least, the changes are related to obliquity-paced solar radiation, manifest as variations in total summer energy. Our findings emphasize solar radiation as a significant driver of mass balance changes in high-latitude mountain systems, and demonstrate that debris-covered glaciers are among the most sensitive recorders of obliquity-paced climate variability in interior Antarctica, in contrast to most other Antarctic archives that favour eccentricity-paced forcing over the same time period. Furthermore, our results open the possibility that similar-appearing debris-covered glaciers on Mars may likewise hold clues to environmental change.
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Project description:The human placenta is covered by a single multinucleated fetal cell, the syncytiotrophoblast, which is bathed in maternal blood. During all pregnancies, membrane enclosed extracellular vesicles derived from the syncytiotrophoblast are extruded into the maternal blood.The large size of these extracellular vesicles (diameter larger than 10µm) is referred to as trophoblastic debris in this study. We have shown in the past that endothleial cells are involved in clearence of this trophoblastic debris and induction of immune tolerence by trophoblastic debris.This study aimed to characterise the transcriptional changes that occur in human vascular endothelial cells following exposure to trophoblastic debris from normal first trimester placentae. Microarrays were used to probe transcriptomic changes 2 and 21 hours after exposure of endothelial cells (Human microvascular endothelial cell line,HMEC-1) to trophoblastic debris from normal first trimester placentae Trophoblastic debris were isolated by low speed centrifugation from three individual first trimester human placentae (three biological replicates). The protein content in trophoblastic debris was measured by BCA assay. HMEC-1 was co-cultured with trophoblastic debris (60ug/ml total debris protein contents) for either 2 or 21 hours before RNA extraction. Untreated HMEC-1 at 2 and 21 hours were used as controls.In total, 12 samples were analyzed.
2016-08-21 | E-GEOD-69996 | biostudies-arrayexpress
Project description:Glacial landforms, including lobate debris aprons, are a global water ice reservoir on Mars preserving ice from past periods when high orbital obliquity permitted nonpolar ice accumulation. Numerous studies have noted morphological similarities between lobate debris aprons and terrestrial debris-covered glaciers, an interpretation supported by radar observations. On Earth and Mars, these landforms consist of a core of flowing ice covered by a rocky lag. Terrestrial debris-covered glaciers advance in response to climate forcing driven by obliquity-paced changes to ice mass balance. However, on Mars, it is not known whether glacial landforms emplaced over the past 300 to 800 formed during a single, long deposition event or during multiple glaciations. Here, we show that boulders atop 45 lobate debris aprons exhibit no evidence of monotonic comminution but are clustered into bands that become more numerous with increasing latitude, debris apron length, and pole-facing flow orientation. Boulder bands are prominent at glacier headwalls, consistent with debris accumulation during the current Martian interglacial. Terrestrial glacier boulder bands occur near flow discontinuities caused by obliquity-driven hiatuses in ice accumulation, forming internal debris layers. By analogy, we suggest that Martian lobate debris aprons experienced multiple cycles of ice deposition, followed by ice destabilization in the accumulation zone, leading to boulder-dominated lenses and subsequent ice deposition and continued flow. Correlation between latitude and boulder clustering suggests that ice mass-balance works across global scales on Mars. Lobate debris aprons may preserve ice spanning multiple glacial/interglacial cycles, extending Mars climate records back hundreds of millions of years.
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Project description:Supraglacial ice cliffs exist on debris-covered glaciers worldwide, but despite their importance as melt hot spots, their life cycle is little understood. Early field observations had advanced a hypothesis of survival of north-facing and disappearance of south-facing cliffs, which is central for predicting the contribution of cliffs to total glacier mass losses. Their role as windows of energy transfer suggests they may explain the anomalously high mass losses of debris-covered glaciers in High Mountain Asia (HMA) despite the insulating debris, currently at the center of a debated controversy. We use a 3D model of cliff evolution coupled to very high-resolution topographic data to demonstrate that ice cliffs facing south (in the Northern Hemisphere) disappear within a few months due to enhanced solar radiation receipts and that aspect is the key control on cliffs evolution. We reproduce continuous flattening of south-facing cliffs, a result of their vertical gradient of incoming solar radiation and sky view factor. Our results establish that only north-facing cliffs are recurrent features and thus stable contributors to the melting of debris-covered glaciers. Satellite observations and mass balance modeling confirms that few south-facing cliffs of small size exist on the glaciers of Langtang, and their contribution to the glacier volume losses is very small ([Formula: see text]1%). This has major implications for the mass balance of HMA debris-covered glaciers as it provides the basis for new parameterizations of cliff evolution and distribution to constrain volume losses in a region where glaciers are highly relevant as water sources for millions of people.
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Project description:High-elevation cold environments are considered ideal places to test hypotheses about mechanisms of bacterial colonization and succession, and about bacterial biogeography. Debris-covered glaciers (glaciers whose ablation area is mainly covered by a continuous layer of rock debris fallen from the surrounding mountains) have never been investigated in this respect so far. We used the Illumina technology to analyse the V5 and V6 hypervariable regions of the bacterial 16S rRNA gene amplified from 38 samples collected in July and September 2009 at different distances from the terminus on two debris-covered glaciers (Miage and Belvedere--Italian Alps). Heterotrophic taxa-dominated communities and bacterial community structure changed according to ice ablation rate, organic carbon content of the debris and distance from the glacier terminus. Bacterial communities therefore change during downwards debris transport, and organic carbon of these recently exposed substrates is probably provided more by allochthonous deposition of organic matter than by primary production by autotrophic organisms. We also investigated whether phylotypes of the genus Polaromonas, which is ubiquitous in cold environments, do present a biogeographical distribution by analysing the sequences retrieved in this study together with others available in the literature. We found that the genetic distance among phylotypes increased with geographic distance; however, more focused analyses using discrete distance classes revealed that both sequences collected at sites <100 km and at sites 9400-13,500 km to each other were more similar than those collected at other distance classes. Evidences of biogeographic distribution of Polaromonas phylotypes were therefore contrasting.
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Project description:Debris-covered glaciers are increasingly studied because it is assumed that debris cover extent and thickness could increase in a warming climate, with more regular rockfalls from the surrounding slopes and more englacial melt-out material. Debris energy-balance models have been developed to account for the melt rate enhancement/reduction due to a thin/thick debris layer, respectively. However, such models require a large amount of input data that are not often available, especially in remote mountain areas such as the Himalaya, and can be difficult to extrapolate. Due to their lower data requirements, empirical models have been used extensively in clean glacier melt modelling. For debris-covered glaciers, however, they generally simplify the debris effect by using a single melt-reduction factor which does not account for the influence of varying debris thickness on melt and prescribe a constant reduction for the entire melt across a glacier. In this paper, we present a new temperature-index model that accounts for debris thickness in the computation of melt rates at the debris-ice interface. The model empirical parameters are optimized at the point scale for varying debris thicknesses against melt rates simulated by a physically-based debris energy balance model. The latter is validated against ablation stake readings and surface temperature measurements. Each parameter is then related to a plausible set of debris thickness values to provide a general and transferable parameterization. We develop the model on Miage Glacier, Italy, and then test its transferability on Haut Glacier d'Arolla, Switzerland. The performance of the new debris temperature-index (DETI) model in simulating the glacier melt rate at the point scale is comparable to the one of the physically based approach, and the definition of model parameters as a function of debris thickness allows the simulation of the nonlinear relationship of melt rate to debris thickness, summarised by the Østrem curve. Its large number of parameters might be a limitation, but we show that the model is transferable in time and space to a second glacier with little loss of performance. We thus suggest that the new DETI model can be included in continuous mass balance models of debris-covered glaciers, because of its limited data requirements. As such, we expect its application to lead to an improvement in simulations of the debris-covered glacier response to climate in comparison with models that simply recalibrate empirical parameters to prescribe a constant across glacier reduction in melt.
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