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Through weathering processes, volcanic rocks contribute both to nutrient flux into the biosphere and atmospheric CO 2 drawdown. As rhyolitic rocks are of higher silica content and have lower concentrations of biologically-important elements than basalts they might be expected to be less easily weathered by a biota. Investigations on the microbial diversity and weathering of silica-rich rhyolitic glass (obsidian) from a lava flow in Iceland are reported. 16S rDNA analysis of rock whole genome DNA shows that the rock hosts remarkable eubacterial diversity. Irregular pitted weathering textures correspond to regions of eubacterial colonization as shown by FISH. Weathering processes proceed at alteration fronts, with a preference for potentially nutrient-rich regions containing plagioclase and pyroxene crystals, although these features are less well defined than those previously reported from basaltic glass, consistent with the lower rates of chemical weathering previously reported for rhyolites compared to ba...

Siliceous and calcareous sponges commonly are treated with acid to remove the spicules prior to embedding and cutting for histological investigations. Histology of spiculated sponge tissue represents a challenging problem in sponge histotechnology. Furthermore, fluorescence in situ hybridization (FISH), a key method for studying sponge-associated microbes, is not possible after acid treatment. For a broad range of siliceous sponge species, we developed and evaluated methods for embedding in paraffin, methylmethacrylate resins, LR White resin and cryomatrix. Different methods for cutting tissue blocks as well as mounting and staining sections also were tested. Our aim was to enable histological investigations and FISH without prior removal of the spicules. To obtain an overview of tissue and skeleton arrangement, we recommend embedding tissue blocks with LR White resin combined with en bloc staining techniques for large specimens with thick and numerous spicules, but paraffin embedding and subsequent staining for whole small specimens. For FISH on siliceous sponges, we recommend Histocryl embedding if the spicule content is high, but paraffin embedding if it is low. Classical histological techniques are used for detailed tissue examinations.

With the appearance of bovine spongiform encephalopathy (BSE) and a new variant of Creutzfeldt-Jakob disease (nvCJD) that seems to be caused by BSE, there is an increased need for improvement of diagnostic techniques and recognition of all variants of prion diseases in humans and animals. Publications on the immunohistochemical identification of PrP(Sc) in the tonsils and appendix in the incubation period of nvCJD indicate that new and more sensitive techniques for the detection of PrP(Sc) in various tissues may be a valuable tool for early diagnosis in prion diseases. We developed a new and sensitive technique to detect PrP(Sc) in formalin-fixed and paraffin-embedded tissue, the paraffin-embedded tissue blot (PET blot), and reinvestigated archival brain material from CJD as well as BSE and scrapie. In addition, C57/Bl6 mice experimentally infected with the ME7 strain were investigated sequentially during the incubation time to compare this new technique with conventional methodologies. The PET blot detects PrP(Sc) in idiopathic (sporadic) and acquired prion diseases, even in cases with equivocal or negative immunohistochemistry, and is more sensitive than the conventional Western blot and histoblot techniques. The PET blot makes possible the detection of PrP(Sc) during the incubation period long before the onset of clinical disease and in prion disease variants with very low levels of PrP(Sc). In mice experimentally infected with the ME7 strain, the PET blot detects PrP(Sc) in the brain 30 days after intracerebral inoculation-145 days before the onset of clinical signs. Its anatomical resolution is superior to that of the histoblot technique. It may therefore be of particular interest in biopsy diagnosis. Thus it complements other tissue-based techniques for the diagnosis of prion diseases in humans and animals.

Fluorescent in situ hybridization (FISH) and 16S rDNA analysis were used to characterize the endolithic colonization of silica-rich rhyolitic glass (obsidian) in a barren terrestrial volcanic environment in Iceland. The rocks were inhabited by a diverse eubacterial assemblage. In the interior of the rock, we identified cyanobacterial and algal 16S (plastid) sequences and visualized phototrophs by FISH, which demonstrates that molecular methods can be used to characterize phototrophs at the limits of photosynthetically active radiation (PAR). Temperatures on the surface of the dark rocks can exceed 40 degrees C but are below freezing for much of the winter. The rocks effectively shield the organisms within from ultraviolet radiation. Although PAR sufficient for photosynthesis cannot penetrate more than approximately 250 mum into the solid rock, the phototrophs inhabit cavities; and we hypothesize that by weathering the rock they may contribute to the formation of cavities in a feedback process, which allows them to acquire sufficient PAR at greater depths. These observations show how pioneer phototrophs can colonize the interior of volcanic glasses and rocks, despite the opaque nature of these materials. The data show that protected microhabitats in volcanic rocky environments would have been available for phototrophs on early Earth.