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

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

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

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

Limits of Principal Components Analysis for Producing a Common Trait Space: Implications for Inferring Selection, Contingency, and Chance in Evolution

&lt;b&gt;Background&lt;/b&gt; Comparing patterns of divergence among separate lineages or groups has posed an especially difficult challenge for biologists. Recently a new, conceptually simple methodology called the “ordered-axis plot” approach was introduced for the purpose of comparing patterns of diversity in a common morphospace. This technique involves a combination of principal components analysis (PCA) and linear regression. Given the common use of these statistics the potential for the widespread use of the ordered axis approach is high. However, there are a number of drawbacks to this approach, most notably that lineages with the greatest amount of variance will largely bias interpretations from analyses involving a common morphospace. Therefore, without meeting a set of a priori requirements regarding data structure the ordered-axis plot approach will likely produce misleading results.&lt;p&gt;&lt;/p&gt; &lt;b&gt;Methodology/Principal Findings&lt;/b&gt; Morphological data sets from cichlid fishes endemic to Lakes Tanganyika, Malawi, and Victoria were used to statistically demonstrate how separate groups can have differing contributions to a common morphospace produced by a PCA. Through a matrix superimposition of eigenvectors (scale-free trajectories of variation identified by PCA) we show that some groups contribute more to the trajectories of variation identified in a common morphospace. Furthermore, through a set of randomization tests we show that a common morphospace model partitions variation differently than group-specific models. Finally, we demonstrate how these limitations may influence an ordered-axis plot approach by performing a comparison on data sets with known alterations in covariance structure. Using these results we provide a set of criteria that must be met before a common morphospace can be reliably used.&lt;p&gt;&lt;/p&gt; &lt;b&gt;Conclusions/Significance&lt;/b&gt; Our results suggest that a common morphospace produced by PCA would not be useful for producing biologically meaningful results unless a restrictive set of criteria are met. We therefore suggest biologists be aware of the limitations of the ordered-axis plot approach before employing it on their own data, and possibly consider other, less restrictive methods for addressing the same question

Tetra­phenyl­phospho­nium hydrogen oxalate

In the title compound, C24H20P+·C2HO4 −, two symmetry-independent ion pairs are present. The cations aggregate into puckered sheets via zigzag infinite chains of sixfold phenyl embraces and parallel fourfold phenyl embraces, while the anions form hydrogen-bonded chains between the sheets of cations. In the two independent oxalate anions, the angles between the normals to the two least-squares carboxyl­ate COO planes are unusually large, viz. 72.5 (1) and 82.1 (1)°