Geobiology of Andean Microbial Ecosystems Discovered in Salar de Atacama, Chile

The Salar de Atacama in the Chilean Central Andes harbors unique microbial ecosystems due to extreme environmental conditions, such as high altitude, low oxygen pressure, high solar radiation, and high salinity. Combining X-ray diffraction analyses, scanning electron microscopy and molecular diversity studies, we have characterized twenty previously unexplored Andean microbial ecosystems in eight different lakes and wetlands from the middle-east and south-east regions of this salt flat. The mats and microbialites studied are mainly formed by calcium carbonate (aragonite and calcite) and halite, whereas the endoevaporites are composed predominantly of gypsum and halite. The carbonate-rich mats and microbialites are dominated by Bacteroidetes and Proteobacteria phyla. Within the phylum Proteobacteria, the most abundant classes are Alphaproteobacteria, Gammaproteobacteria and Deltaproteobacteria. While in the phylum Bacteroidetes, the most abundant classes are Bacteroidia and Rhodothermia. Cyanobacteria, Chloroflexi, Planctomycetes, and Verrucomicrobia phyla are also well-represented in the majority of these systems. Gypsum endoevaporites, on the contrary, are dominated by Proteobacteria, Bacteroidetes, and Euryarchaeota phyla. The Cyanobacteria phylum is also abundant in these systems, but it is less represented in comparison to mats and microbialites. Regarding the eukaryotic taxa, diatoms are key structural components in most of the microbial ecosystems studied. The genera of diatoms identified were Achnanthes, Fallacia, Halamphora, Mastogloia, Navicula, Nitzschia, and Surirella. Normally, in the mats and microbialites, diatoms form nano-globular carbonate aggregates with filamentous cyanobacteria and other prokaryotic cells, suggesting their participation in the mineral precipitation process. This work expands our knowledge of the microbial ecosystems inhabiting the extreme environments from the Central Andes region, which is important to ensure their protection and conservation.

The structure and thermal properties of tmfe2o4 at different values of temperature and oxygen pressure

The stability range of TmFe2O4 has been studied under conditions of low oxygen pressure in the gas phase at the temperature of 1090 °C. The thermodynamic characteristics of thulium ferrite are calculated from experimental data obtained during dissociation of the compound in the temperature range of 750–900 °C. Structural transformations are determined in the temperature range from –140 to 140 °C. They are associated with charge ordering in this compound.

Living conditions in high altitude waters

Chapter 3 deals with the abiotic environment in high altitude lakes and streams worldwide. It searches for general patterns in relation to altitude, without overlooking the enormous variability, both temporally as well as at small and large spatial scales. Overall, environmental conditions in high altitude waters may be regarded as harsh. Indeed, certain features such as low temperature, low oxygen pressure, and high ultraviolet radiation (all a direct result of high altitude) as well as transparent and ion-poor waters with low nutrient concentrations are typical of high altitude aquatic systems. However, streams and lakes turbid from inflow of glacial meltwater loaded with glacial mineral flour and peatbogs with deep brown water from a high concentration of coloured dissolved organic matter are equally prominent. So, evidently, environmental conditions in aquatic systems are probably just as variable at high as at low altitudes.