Evidence of global-scale aeolian dispersal and endemism in isolated geothermal microbial communities of Antarctica

New evidence in aerobiology challenges the assumption that geographical isolation is an effective barrier to microbial transport. However, given the uncertainty with which aerobiological organisms are recruited into existing communities, the ultimate impact of microbial dispersal is difficult to assess. To evaluate the ecological significance of global-scale microbial dispersal, molecular genetic approaches were used to examine microbial communities inhabiting fumarolic soils on Mt. Erebus, the southernmost geothermal site on Earth. There, hot, fumarolic soils provide an effective environmental filter to test the viability of organisms that have been distributed via aeolian transport over geological time. We find that cosmopolitan thermophiles dominate the surface, whereas endemic Archaea and members of poorly understood Bacterial candidate divisions dominate the immediate subsurface. These results imply that aeolian processes readily disperse viable organisms globally, where they are incorporated into pre-existing complex communities of endemic and cosmopolitan taxa

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

Influence of soil properties on archaeal diversity and distribution in the McMurdo Dry Valleys, Antarctica

Archaea are the least understood members of the microbial community in Antarctic mineral soils. Although their occurrence in Antarctic coastal soils has been previously documented, little is known about their distribution in soils across the McMurdo Dry Valleys, Victoria Land. In this study, terminal-restriction fragment length polymorphism (t-RFLP) analysis and 454 pyrosequencing were coupled with a detailed analysis of soil physicochemical properties to characterize archaeal diversity and identify environmental factors that might shape and maintain archaeal communities in soils of the three southern most McMurdo Dry Valleys (Garwood, Marshall, and Miers Valley). Archaea were successfully detected in all inland and coastal mineral soils tested, revealing a low overall richness (mean of six operational taxonomic units [OTUs] per sample site). However, OTU richness was higher in some soils and this higher richness was positively correlated with soil water content, indicating water as a main driver of archaeal community richness. In total, 18 archaeal OTUs were detected, predominately Thaumarchaeota affiliated with Marine Group 1.1b (> 80% of all archaeal sequences recovered). Less abundant OTUs (2% of all archaeal sequences) were loosely related to members of the phylum Euryarchaeota. This is the first comprehensive study showing a widespread presence and distribution of Archaea in inland Antarctic soils

Oxidation processes in magneto-optic and related materials

The surface oxidation processes of thin films of magneto-optic materials, such as the rare-earth transition metal alloys have been studied, starting in ultrahigh vacuum environments, using surface analysis techniques, as a way of modeling the oxidation processes which occur at the base of a defect in an overcoated material, at the instant of exposure to ambient environments. Materials examined have included FeTbCo alloys, as well as those same materials with low percentages of added elements, such a Ta, and their reactivities to both O2 and H2O compared with materials such as thin Fe films coated with ultrathin adlayers of Ti. The surface oxidation pathways for these materials is reviewed, and XPS data presented which indicates the type of oxides formed, and a critical region of Ta concentration which provides optimum protection

Groundtruthing next-gen sequencing for microbial ecology-biases and errors in community structure estimates from PCR amplicon pyrosequencing

Analysis of microbial communities by high-throughput pyrosequencing of SSU rRNA gene PCR amplicons has transformed microbial ecology research and led to the observation that many communities contain a diverse assortment of rare taxa-a phenomenon termed the Rare Biosphere. Multiple studies have investigated the effect of pyrosequencing read quality on operational taxonomic unit (OTU) richness for contrived communities, yet there is limited information on the fidelity of community structure estimates obtained through this approach. Given that PCR biases are widely recognized, and further unknown biases may arise from the sequencing process itself, a priori assumptions about the neutrality of the data generation process are at best unvalidated. Furthermore, post-sequencing quality control algorithms have not been explicitly evaluated for the accuracy of recovered representative sequences and its impact on downstream analyses, reducing useful discussion on pyrosequencing reads to their diversity and abundances. Here we report on community structures and sequences recovered for in vitro-simulated communities consisting of twenty 16S rRNA gene clones tiered at known proportions. PCR amplicon libraries of the V3-V4 and V6 hypervariable regions from the in vitro-simulated communities were sequenced using the Roche 454 GS FLX Titanium platform. Commonly used quality control protocols resulted in the formation of OTUs with >1% abundance composed entirely of erroneous sequences, while over-aggressive clustering approaches obfuscated real, expected OTUs. The pyrosequencing process itself did not appear to impose significant biases on overall community structure estimates, although the detection limit for rare taxa may be affected by PCR amplicon size and quality control approach employed. Meanwhile, PCR biases associated with the initial amplicon generation may impose greater distortions in the observed community structure

Visualization of flows in a motored rotary combustion engine using holographic interferometry

The use of holographic interferometry to view the small- and large-scale flow field structures in the combustion chamber of a motored Wankel engine assembly is described. In order that the flow patterns of interest could be observed, small quantities of helium were injected with the intake air. Variation of the air flow patterns with engine speed, helium flow rate, and rotor position are described. The air flow at two locations within the combustion chamber was examined using this technique

Cytochrome P450 Derived Eicosanoids, Endothelial Function and Cardiovascular Disease

Endothelial dysfunction plays an integral role in the pathogenesis and progression of cardiovascular disease in humans. The development of endothelial dysfunction has been primarily ascribed to functional impairments in nitric oxide biosynthesis. However, arachidonic acid metabolism by the cyclooxygenase and cytochrome P450 epoxygenase pathways also appears to regulate endothelial function. Consequently, genetic variation in these pathways may be important modifiers of cardiovascular disease risk in humans. The collective objective of the studies outlined in this doctoral dissertation was to determine if genetic variation in these established (NOS3, PTGS1 and PTGS2) and recently characterized (EPHX2, CYP2J2 and CYP2C8) pathways are significantly associated with cardiovascular disease risk. First, metabolic studies conducted in vitro demonstrate that certain genetic variants in cyclooxygenase-1 possess significantly lower metabolic activity compared to wild-type cyclooxygenase-1. Second, the observed associations between genetic variation in PTGS1, PTGS2 and NOS3 and risk of incident coronary heart disease and ischemic stroke events further implicate these established pathways in the development of cardiovascular disease in humans. Third, the observed associations between genetic variation in EPHX2, CYP2J2 and CYP2C8 and risk of incident coronary heart disease events also demonstrate the potential importance of the cytochrome P450 epoxygenase pathway in the pathogenesis of ischemic cardiovascular disease in humans. Fourth, the development and baseline characterization of transgenic mice that exhibit vascular endothelial cell-specific overexpression of either human CYP2J2 or CYP2C8 will enable further mechanistic characterization of the cytochrome P450 epoxygenase pathway in the regulation of endothelial function and the pathogenesis of cardiovascular disease

Differential Mass Measurement Scale for Measuring Refrigerant Charge and Oil Retention of Round Tube Plate Fin Heat Exchangers (ASHRAE RP-1785)

During the product development process of split-system air-conditioning units, simulation models are widely used by manufacturers to predict equipment performance. Model-based development allows manufacturers to reduce the number of experiments prior to product launch, reducing product development cycle time and cost. However, the current models struggle to predict performance for reversible heat pump systems because of inaccurate predictions of refrigerant charge and oil retention. This is due to a lack of validation data for R410A charge models. This study provides high-quality reference data for refrigerant and oil charge measurements in residential fin-tube heat exchangers operating with R410A. This high-quality reference data will allow tuning of simulation models to improve charge prediction accuracy. As a result, the data will enable enhanced simulation model development with better charge and performance prediction capabilities, reducing product development cost for our industry. A key component, the Differential Mass Measurement Scale (DMMS) with 0.006% of relative accuracy of 49.9 kg tare weight of a heat exchanger test module, to implement this method is presented