The discovery of Stromatolites developing at 3570 m above sea level in a high-altitude volcanic lake Socompa, Argentinean Andes

We describe stromatolites forming at an altitude of 3570 m at the shore of a volcanic lake Socompa, Argentinean Andes. The water at the site of stromatolites formation is alkaline, hypersaline, rich in inorganic nutrients, very rich in arsenic, and warm (20-24°C) due to a hydrothermal input. The stromatolites do not lithify, but form broad, rounded and low-domed bioherms dominated by diatom frustules and aragonite micro-crystals agglutinated by extracellular substances. In comparison to other modern stromatolites, they harbour an atypical microbial community characterized by highly abundant representatives of Deinococcus-Thermus, Rhodobacteraceae, Desulfobacterales and Spirochaetes. Additionally, a high proportion of the sequences that could not be classified at phylum level showed less than 80% identity to the best hit in the NCBI database, suggesting the presence of novel distant lineages. The primary production in the stromatolites is generally high and likely dominated by Microcoleus sp. Through negative phototaxis, the location of these cyanobacteria in the stromatolites is controlled by UV light, which greatly influences their photosynthetic activity. Diatoms, dominated by Amphora sp., are abundant in the anoxic, sulfidic and essentially dark parts of the stromatolites. Although their origin in the stromatolites is unclear, they are possibly an important source of anaerobically degraded organic matter that induces in situ aragonite precipitation. To the best of our knowledge, this is so far the highest altitude with documented actively forming stromatolites. Their generally rich, diverse and to a large extent novel microbial community likely harbours valuable genetic and proteomic reserves, and thus deserves active protection. Furthermore, since the stromatolites flourish in an environment characterized by a multitude of extremes, including high exposure to UV radiation, they can be an excellent model system for studying microbial adaptations under conditions that, at least in part, resemble those during the early phase of life evolution on Earth.Instituto de Biotecnologia y Biologia Molecular (IBBM

La renovación de la palabra en el bicentenario de la Argentina : los colores de la mirada lingüística

El libro reúne trabajos en los que se exponen resultados de investigaciones presentadas por investigadores de Argentina, Chile, Brasil, España, Italia y Alemania en el XII Congreso de la Sociedad Argentina de Lingüística (SAL), Bicentenario: la renovación de la palabra, realizado en Mendoza, Argentina, entre el 6 y el 9 de abril de 2010. Las temáticas abordadas en los 167 capítulos muestran las grandes líneas de investigación que se desarrollan fundamentalmente en nuestro país, pero también en los otros países mencionados arriba, y señalan además las áreas que recién se inician, con poca tradición en nuestro país y que deberían fomentarse. Los trabajos aquí publicados se enmarcan dentro de las siguientes disciplinas y/o campos de investigación: Fonología, Sintaxis, Semántica y Pragmática, Lingüística Cognitiva, Análisis del Discurso, Psicolingüística, Adquisición de la Lengua, Sociolingüística y Dialectología, Didáctica de la lengua, Lingüística Aplicada, Lingüística Computacional, Historia de la Lengua y la Lingüística, Lenguas Aborígenes, Filosofía del Lenguaje, Lexicología y Terminología

Stratified bacterial diversity along physico-chemical gradients in high-altitude modern stromatolites.

At an altitude of 3,570 m, the volcanic lake Socompa in the Argentinean Andes is presently the highest site where actively forming stromatolite-like structures have been reported. Interestingly, pigment and microsensor analyses performed through the different layers of the stromatolites (50 mm-deep) showed steep vertical gradients of light and oxygen, hydrogen sulfide and pH in the porewater. Given the relatively good characterization of these physico-chemical gradients, the aim of this follow-up work was to specifically address how the bacterial diversity stratified along the top six layers of the stromatolites which seems the most metabolically important and diversified zone of the whole microbial community. We herein discussed how, in only 7 mm, a drastic succession of metabolic adaptations occurred: i.e., microbial communities shift from a UV-high/oxic world to an IR-low/anoxic/high H2S environment which force stratification and metabolic specialization of the bacterial community, thus, modulating the chemical faces of the Socompa stromatolites. The oxic zone was dominated by Deinococcus sp. at top surface (0.3 mm), followed by a second layer of Coleofasciculus sp. (0.3 to ∼2 mm). Sequences from anoxygenic phototrophic Alphaproteobacteria, along with an increasing diversity of phyla including Bacteroidetes, Spirochaetes were found at middle layers 3 and 4. Deeper layers (5–7 mm) were mostly occupied by sulfate reducers of Deltaproteobacteria, Bacteroidetes and Firmicutes, next to a high diversity and equitable community of rare, unclassified and candidate phyla. This analysis showed how microbial communities stratified in a physicochemical vertical profile and according to the light source. It also gives an insight of which bacterial metabolic capabilities might operate and produce a microbial cooperative strategy to thrive in one of the most extreme environments on Earth

Stratified bacterial diversity along physico-chemical gradients in high-altitude modern stromatolites.

At an altitude of 3,570 m, the volcanic lake Socompa in the Argentinean Andes is presently the highest site where actively forming stromatolite-like structures have been reported. Interestingly, pigment and microsensor analyses performed through the different layers of the stromatolites (50 mm-deep) showed steep vertical gradients of light and oxygen, hydrogen sulfide and pH in the porewater. Given the relatively good characterization of these physico-chemical gradients, the aim of this follow-up work was to specifically address how the bacterial diversity stratified along the top six layers of the stromatolites which seems the most metabolically important and diversified zone of the whole microbial community. We herein discussed how, in only 7 mm, a drastic succession of metabolic adaptations occurred: i.e., microbial communities shift from a UV-high/oxic world to an IR-low/anoxic/high H2S environment which force stratification and metabolic specialization of the bacterial community, thus, modulating the chemical faces of the Socompa stromatolites. The oxic zone was dominated by Deinococcus sp. at top surface (0.3 mm), followed by a second layer of Coleofasciculus sp. (0.3 to ∼2 mm). Sequences from anoxygenic phototrophic Alphaproteobacteria, along with an increasing diversity of phyla including Bacteroidetes, Spirochaetes were found at middle layers 3 and 4. Deeper layers (5–7 mm) were mostly occupied by sulfate reducers of Deltaproteobacteria, Bacteroidetes and Firmicutes, next to a high diversity and equitable community of rare, unclassified and candidate phyla. This analysis showed how microbial communities stratified in a physicochemical vertical profile and according to the light source. It also gives an insight of which bacterial metabolic capabilities might operate and produce a microbial cooperative strategy to thrive in one of the most extreme environments on Earth

Effect of UV irradiation on the distribution and activity of cyanobateria in the stromatolites.

<p>(A–D) Appearance of the stromatolite surface under various light conditions: (A) full ambient light at 3500 masl, (B) after 1–2 hours of incubation in a shade at 3500 masl, (C) after 5 days of incubation at ambient light conditions with the UV light intensity reduced by about 30% (at 460 masl), (D) after 2–3 hours of exposure to artificial UV-B radiation at 460 masl. Note that because of the extremely dark-green appearance of the surface in panel C (reflectance <1%), the brightness of the shown image was increased 5-fold. (E–G) Vertical distributions of Chl <i>a</i> in the stromatolite obtained by hyperspectral imaging and HPLC. Panels E and F correspond to samples shown in panels A and B, while open and closed symbols in panel G correspond to samples shown in panels A and C, respectively. (H–I) Steady state profiles of oxygen and of the volumetric rates of net photosynthesis (net PS) in the freshly collected (shown in A) and modified (shown in C) stromatolite. Shown are profiles measured at incident PAR intensities of 600 µmol photons m⁻² s⁻¹ (open symbols and bars) and in the dark (filled symbols and bars). Note the 10-fold difference in the scaling of the net PS axis.</p

Typical profiles of scalar irradiance (E_s), O₂, pH and H₂S in the Socompa stromatolites, as measured with microsensors in the field at 3500 masl.

<p>(A) E_s was normalized to the value at the stromatolite surface, and is shown for selected wavelengths (see legend). E_s in the UV region was estimated based on the profiles measured at 676 nm and 750 nm. (B–C) Steady state profiles of O₂ and pH were measured at 25°C. Incident intensity of the ambient PAR was 130 W m⁻² (corresponding to 600 µmol photons m⁻² s⁻¹). (D) Transient profiles of H₂S were measured in a shaded place (PAR intensity <50 µmol photons m⁻² s⁻¹) during gradually increasing ambient temperature (see legend). For all measurements salinity of the overlying water was 48 g L⁻¹, as estimated from the measured conductivity (70 mS cm⁻¹) assuming seawater salt composition. Due to the lack of calibration standards, H₂S is given only as a raw signal linearly proportional to H₂S concentrations. Depth 0 corresponds to the stromatolite surface. Note the 10-fold difference in the depth scale in panels A–B and C–D.</p

Distributions of pigments in the Socompa stromatolites.

<p>(A) Vertical section of the stromatolite sample measured by HPLC, with the corresponding pigment profiles shown in panels B–C. Dashed horizontal lines indicate boundaries of the sampled layers. The scaling of the concentration axis differs between pigments: c_max = 70, 2.1, 7 and 400 µg (g dw) ⁻¹ for Chl <i>a</i>, Bchl <i>a</i>, Bchl <i>c</i> and phycocyanin, respectively. β-carotene and focoxanthin are given in relative units only. Note that pigment concentrations are not shown in the top layer (0–0.33 mm) because they could not be measured by HPLC due to an insufficient amount of sample. In this layer, the Chl <i>a</i> concentration was estimated based on the profile derived from hyper-spectral imaging as 10% of the maximum (dashed line). (D–G) True-color and the corresponding false-color pigment images, obtained by hyper-spectral imaging of two additional stromatolite samples. Intensity of the red, green and blue colors in images E and G is proportional to the concentration of Chl <i>a</i>, Bchl <i>c</i> and Bchl <i>a</i>, respectively. Scale bar = 5 mm in all images.</p

Basic physico-chemical and biological characteristics of the water samples from the Socompa lake (site 5 in Figure 1) and from the hydrothermal spring (HTS).

<p>Basic physico-chemical and biological characteristics of the water samples from the Socompa lake (site 5 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053497#pone-0053497-g001" target="_blank">Figure 1</a>) and from the hydrothermal spring (HTS).</p

Relatedness of the <i>nif</i>H and <i>amo</i>A gene sequences detected in the Socompa stromatolites to those in the most closely related cultivated isolates and to the closest hits in the NCBI database.

<p>Relatedness of the <i>nif</i>H and <i>amo</i>A gene sequences detected in the Socompa stromatolites to those in the most closely related cultivated isolates and to the closest hits in the NCBI database.</p