Characterization of the bacterioplankton communities in the melt-water ponds of Bratina Island, Victoria Land, Antarctica

Antarctic ecosystems (such as the ponds by Bratina Island, Antarctica) provide an excellent opportunity to examine organisms that can live in one of the most extreme and geochemically varied environments in the world. These ponds are of interest as each one can vary greatly in size, depth, and age as well as profiles of dissolved oxygen, metal concentrations, pH and salinity. Even within ponds geochemically distinct stratified layers can form which can greatly influence their microbial communities. There are a number of studies which indicate that microbial populations found in Antarctic ponds will be highly diverse and variable due to the uniqueness of the environment. This study aims to increase our knowledge of microbial biodiversity and the environmental factors which structure them, in particular the stratification transition zones within ponds water columns. A thorough set of biological samples were taken from five selected ponds during mid-summer in the 09-10 season to complement those taken during the winter freeze-up in the 07-08 extended season by Hawes and co-workers. Oxygen concentration, pH, conductivity and temperature of each pond water sample were measured in the field and water samples were taken back to the University of Waikato for further analysis. This research primarily used the DNA fingerprinting technique ARISA, matched with geochemistry to identify and characterise the resident and functional members of the microbial community and understand how the community is structured in relation to environmental conditions. We found that the planktonic populations of the Bratina Island ponds do vary between ponds, that each pond has its own chemical signature and that populations do change with depth. One of the studied ponds, Egg, was found to have an extreme chemical stratification leading to significantly different populations at each depth. Data analysis using BEST analysis determined that the changes in the bacterial populations in Egg are primarily in relation to the pH and conductivity at each depth which changes dramatically in the lower depths

Characterisation of bacterioplankton communities in the meltwater ponds of Bratina Island, Victoria Land, Antarctica

A unique collection of Antarctic aquatic environments (meltwater ponds) lies in close proximity on the rock and sediment-covered undulating surface of the McMurdo Ice Shelf, near Bratina Island (Victoria Land, Antarctica). During the 2009–10 mid-austral summer, sets of discrete water samples were collected across the vertical geochemical gradients of five meltwater ponds (Egg, P70E, Legin, Salt and Orange) for geochemical and microbial community structure analysis. Bacterial DNA fingerprints (using Automated Ribosomal Intergenic Spacer Analysis) statistically clustered communities within ponds based on ANOSIM (R = 0.766, P = 0.001); however, one highly stratified pond (Egg) had two distinct depth-related bacterial communities (R = 0.975, P = 0.008). 454 pyrosequencing at three depths within Egg also identified phylum level shifts and increased diversity with depth, Bacteroidetes being the dominant phyla in the surface sample and Proteobacteria being dominant in the bottom two depths. BEST analysis, which attempts to link community structure and the geochemistry of a pond, identified conductivity and pH individually, and to a lesser extent Ag109, NO2 and V51 as dominant influences to the microbial community structure in these ponds. Increasing abundances of major halo-tolerant OTUs across the strong conductivity gradient reinforce it as the primary driver of community structure in this stud

MECHANISMS OF DISEASE Acute Oxygen-Sensing Mechanisms

JOSEPH PRIESTLEY, ONE OF THE THREE SCIENTISTS CREDITED WITH THE discovery of oxygen, described the death of mice that were deprived of oxygen. However, he was also well aware of the toxicity of too much oxygen, stating, “For as a candle burns much faster in dephlogisticated [oxygen enriched] than in common air, so we might live out too fast, and the animal powers be too soon exhausted in this pure kind of air. A moralist, at least, may say, that the air which nature has provided for us is as good as we deserve.”1 In this review we examine the remarkable mechanisms by which different organs detect and respond to acute changes in oxygen tension. Specialized tissues that sense the local oxygen tension include glomus cells of the carotid body, neuroepithelial bodies in the lungs, chromaffin cells of the fetal adrenal medulla, and smooth-muscle cells of the resistance pulmonary arteries, fetoplacental arteries, systemic arteries, and the ductus arteriosus. Together, they constitute a specialized homeostatic oxygen-sensing system. Although all tissues are sensitive to severe hypoxia, these specialized tissues respond rapidly to moderate changes in oxygen tension within the physiologic range (roughly 40 to 100 mm Hg in an adult and 20 to 40 mm Hg in a fetus)Junta de Andalucí

Visual feedback alters force control and functional activity in the visuomotor network after stroke.

Modulating visual feedback may be a viable option to improve motor function after stroke, but the neurophysiological basis for this improvement is not clear. Visual gain can be manipulated by increasing or decreasing the spatial amplitude of an error signal. Here, we combined a unilateral visually guided grip force task with functional MRI to understand how changes in the gain of visual feedback alter brain activity in the chronic phase after stroke. Analyses focused on brain activation when force was produced by the most impaired hand of the stroke group as compared to the non-dominant hand of the control group. Our experiment produced three novel results. First, gain-related improvements in force control were associated with an increase in activity in many regions within the visuomotor network in both the stroke and control groups. These regions include the extrastriate visual cortex, inferior parietal lobule, ventral premotor cortex, cerebellum, and supplementary motor area. Second, the stroke group showed gain-related increases in activity in additional regions of lobules VI and VIIb of the ipsilateral cerebellum. Third, relative to the control group, the stroke group showed increased activity in the ipsilateral primary motor cortex, and activity in this region did not vary as a function of visual feedback gain. The visuomotor network, cerebellum, and ipsilateral primary motor cortex have each been targeted in rehabilitation interventions after stroke. Our observations provide new insight into the role these regions play in processing visual gain during a precisely controlled visuomotor task in the chronic phase after stroke

Contribution of soil bacteria to the atmosphere across biomes

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboración, si lo hubiereThe dispersion of microorganisms through the atmosphere is a continual and essential process that underpins biogeography and ecosystem development and function. Despite the ubiquity of atmospheric microorganisms globally, specific knowledge of the determinants of atmospheric microbial diversity at any given location remains unresolved. Here we describe bacterial diversity in the atmospheric boundary layer and underlying soil at twelve globally distributed locations encompassing all major biomes, and characterise the contribution of local and distant soils to the observed atmospheric community. Across biomes the diversity of bacteria in the atmosphere was negatively correlated with mean annual precipitation but positively correlated to mean annual temperature. We identified distinct non-randomly assembled atmosphere and soil communities from each location, and some broad trends persisted across biomes including the enrichment of desiccation and UV tolerant taxa in the atmospheric community. Source tracking revealed that local soils were more influential than distant soil sources in determining observed diversity in the atmosphere, with more emissive semi-arid and arid biomes contributing most to signatures from distant soil. Our findings highlight complexities in the atmospheric microbiota that are relevant to understanding regional and global ecosystem connectivityThis work was supported by the Singapore Ministry of Education and Yale-NUS College, grant number R-607-265-331-12

Benthic microbial communities of coastal terrestrial and ice shelf Antarctic meltwater ponds.

The numerous perennial meltwater ponds distributed throughout Antarctica represent diverse and productive ecosystems central to the ecological functioning of the surrounding ultra oligotrophic environment. The dominant taxa in the pond benthic communities have been well described however, little is known regarding their regional dispersal and local drivers to community structure. The benthic microbial communities of 12 meltwater ponds in the McMurdo Sound of Antarctica were investigated to examine variation between pond microbial communities and their biogeography. Geochemically comparable but geomorphologically distinct ponds were selected from Bratina Island (ice shelf) and Miers Valley (terrestrial) (<40 km between study sites), and community structure within ponds was compared using DNA fingerprinting and pyrosequencing of 16S rRNA gene amplicons. More than 85% of total sequence reads were shared between pooled benthic communities at different locations (OTU0.05), which in combination with favorable prevailing winds suggests aeolian regional distribution. Consistent with previous findings Proteobacteria and Bacteroidetes were the dominant phyla representing over 50% of total sequences; however, a large number of other phyla (21) were also detected in this ecosystem. Although dominant Bacteria were ubiquitous between ponds, site and local selection resulted in heterogeneous community structures and with more than 45% of diversity being pond specific. Potassium was identified as the most significant contributing factor to the cosmopolitan community structure and aluminum to the location unique community based on a BEST analysis (Spearman's correlation coefficient of 0.632 and 0.806, respectively). These results indicate that the microbial communities in meltwater ponds are easily dispersed regionally and that the local geochemical environment drives the ponds community structure

Identify the opportunities provided by developments in earth observation and remote sensing for national scale monitoring of soil quality

Defra wish to establish to what extent national-scale soil monitoring (both state and change) of a series of soil indicators might be undertaken by the application of remote sensing methods. Current soil monitoring activities rely on the field-based collection and laboratory analysis of soil samples from across the landscape according to different sampling designs. The use of remote sensing offers the potential to encompass a larger proportion of the landscape, but the signal detected by the remote sensor has to be converted into a meaningful soil measurement which may have considerable uncertainty associated with it. The eleven soil indicators which were considered in this report are pH, organic carbon, bulk density, phosphorus (Olsen P), nitrogen (total N), magnesium (extractable), potassium (extractable), copper (aqua regia extractable), cadmium (aqua regia extractable), zinc (aqua regia extractable) and nickel (aqua regia extractable). However, we also comment on the potential use of remote sensing for monitoring of soil depth and (in particular) peat depth, plus soil erosion and compaction. In assessing the potential of remote sensing methods for soil monitoring of state and change, we addressed the following questions: 1. When will these be ready for use and what level of further development is required? 2. Could remote sensing of any of these indicators replace and/or complement traditional field based national scale soil monitoring? 3. Can meaningful measures of change be derived? 4. How could remote soil monitoring of individual indicators be incorporated into national scale soil monitoring schemes? To address these questions, we undertook a comprehensive literature and internet search and also wrote to a range of international experts in remote sensing. It is important to note that the monitoring of the status of soil indicators, and the monitoring of their change, are two quite different challenges; they are different variables and their variability is likely to differ. There are particular challenges to the application of remote sensing of soil in northern temperate regions (such as England and Wales), including the presence of year-round vegetation cover which means that soil spectral reflectance cannot be captured by airborne or satellite observations, and long-periods of cloud cover which limits the application of satellite-based spectroscopy. We summarise the potential for each of the indicators, grouped where appropriate. Unless otherwise stated, the remote sensing methods would need to be combined with ground-based sampling and analysis to make a contribution to detection of state or change in soil indicators. Soil metals (copper (Cu), cadmium (Cd), zinc (Zn), nickel (Ni)): there is no technical basis for applying current remote sensing approaches to monitor either state or change of these indicators and there are no published studies which have shown how this might be achieved. Soil nutrients: the most promising remote sensing technique to improve estimates of the status of extractable potassium (K) is the collection and application of airborne radiometric survey (detection of gamma radiation by low-flying aircraft) but this should be investigated further. This is unlikely to assist in monitoring change. Based on published literature, it may be possible to enhance mapping the state of extractable magnesium (Mg), but not to monitor change, using hyperspectral (satellite or airborne) remote sensing in cultivated areas. This needs to be investigated further. There are no current remote sensing methods for detecting state or change of Olsen (extractable) phosphorus (P). Organic carbon and total nitrogen: Based on published literature, it may be possible to enhance mapping the state of organic carbon and total nitrogen (but not to monitor change), using hyperspectral (satellite or airborne) remote sensing in cultivated areas only. In applying this approach the satellite data are applied using a statistical model which is trained using ground-based sampling and analysis of soil

Geochemical, Spatial, and Temporal Drivers of Microbial Community Heterogeneity in the Meltwater Ponds of Antarctica

Antarctic meltwater ponds are an abundant, dynamic and sensitive yet poorly understood ecosystem. In this thesis, bacterial communities from surface waters, the water column and benthic zone in geochemically variable meltwater ponds in the Ross Sea Region of Antarctica were investigated. The primary objective of this research was to provide a detailed description of the community composition and to determine the temporal, geochemical and geomorphological drivers of community structure. A coordinated comparable analysis method was used for all samples so that, although separated into the previously mentioned zones, findings could be directly compared across studies. Bacterial community structure between samples was initially investigated by Automated Ribosomal Intergenic Spacer Analysis (ARISA) of the 16S rRNA gene which, combined with in-situ collected geochemistry data was used to identify trends requiring high throughput sequencing (454 pyrosequencing of the V5-V6 hypervariable region of the 16S rRNA gene) analysis coupled with nutrient and elemental data. A preliminary study in December 2009 compared the water columns of five geochemically distinct ponds. Communities between ponds were distinct, their structure driven primarily by pH and conductivity. One geochemically stratified pond formed distinct surface and bottom clusters with increasing diversity and changes to phyla structure with depth. Temporal and geomorphological (Bratina Island and Miers Valley) drivers of variation in the microbial community structure between the surface waters of 41 ponds were examined. Conductivity was identified as the most significant driver across all ponds for the dominant cosmopolitan community, however trace elements were more significant drivers of community structure for the unique community (those sequences absent in at least one pond). Pronounced variation was identified between December and January samples and although the bacterial components of the community were similar between January 2012 and 2013 the community structure varied significantly. Despite different environments, communities from the Miers Valley were not well differentiated from Bratina Island, suggesting biological exchange between locations. The stratified water column of six Bratina Island and two Miers Valley ponds was investigated. Strongly geochemically stratified ponds exhibited a heterogeneous vertical community structure related to conductivity and dissolved oxygen. Variation in community structure was primarily driven by the abundance of a small number of cosmopolitan OTUs that changed with depth. Although the biological constituents were the same, minor variation in community structure was identified within Huey pond between years (2012 and 2013). Variation between Huey pond (Bratina Island) and Morepork pond (Miers Valley) was correlated with variation of iron and mercury concentration. Lastly the benthic zone of six ponds from Bratina Island and six from the Miers Valley was examined. The community structure was highly heterogeneous and diverse with 21 phyla identified. No distinction was identified between the two locations with the majority of pyrosequencing reads shared. Potassium, sodium and cobalt were identified as the most significant explanatory variables to the cosmopolitan community and aluminium, uranium and magnesium to the unique community. This study has granted an unprecedented understanding of the bacterial communities in the meltwater ponds of the Ross Sea Region. Geochemical inter pond heterogeneity is matched with an equally heterogeneous bacterial communities, primarily driven by conductivity. Although harboring a complex and diverse community the majority is comprised of a small number of shared OTUs across spatial and temporal scales