Biogeochemical cycles (C, N, S, P and Fe) of modern and ancient microbialites (Western Australia)

This PhD study focused on organic, inorganic and isotopic geochemical studies of modern stromatolites from Shark Bay, Western Australia (WA) and ancient stromatolites from the Pilbara, WA. In this project, the characterisation of microbial communities, biogeochemical cycles and influence of environmental conditions on microbial mat functioning were investigated. In addition, the preservation pathways of biosignatures in microbialites through time were explored, providing a better insight into the evolution of early-life

Sustained increases in atmospheric oxygen and marine productivity in the Neoproterozoic and Palaeozoic eras

A geologically rapid Neoproterozoic oxygenation event is commonly linked to the appearance of marine animal groups in the fossil record. However, there is still debate about what evidence from the sedimentary geochemical record—if any—provides strong support for a persistent shift in surface oxygen immediately preceding the rise of animals. We present statistical learning analyses of a large dataset of geochemical data and associated geological context from the Neoproterozoic and Palaeozoic sedimentary record and then use Earth system modelling to link trends in redox-sensitive trace metal and organic carbon concentrations to the oxygenation of Earth’s oceans and atmosphere. We do not find evidence for the wholesale oxygenation of Earth’s oceans in the late Neoproterozoic era. We do, however, reconstruct a moderate long-term increase in atmospheric oxygen and marine productivity. These changes to the Earth system would have increased dissolved oxygen and food supply in shallow-water habitats during the broad interval of geologic time in which the major animal groups first radiated. This approach provides some of the most direct evidence for potential physiological drivers of the Cambrian radiation, while highlighting the importance of later Palaeozoic oxygenation in the evolution of the modern Earth system

A molecular and isotopic study of palaeoenvironmental conditions through the middle Cambrian in the Georgina Basin, Central Australia

The Cambrian period marks an important point in Earth's history with profound changes in the ocean's biogeochemistry and the occurrence of the most significant evolutionary event in the history of life, the Cambrian explosion. The Cambrian explosion is described as a succession of complex cycles of extinctions and radiations. This study integrates biomarkers and their compound-specific stable carbon isotopes to investigate the palaeoenvironmental depositional conditions in middle Cambrian (Series 3) sedimentary rocks (Thorntonia Limestone, Inca Formation and Currant Bush Limestone) from two drillholes in the Undilla Sub-basin in the eastern Georgina Basin, central Australia. The occurrence of photic zone euxinia (PZE) was detected throughout these three formations by the identification of green sulfur bacteria Chlorobiaceae-derived biomarkers, including a series of 2,3,6-aryl isoprenoids and the intact biomarker isorenieratane. Pulses of enhanced PZE conditions were detected in two core intervals (90-110 mKB, Currant Bush Limestone and 170-200 mKB, Inca Formation) by an increase in the 2,3,6-aryl isoprenoids and C19 biphenyl concentrations. These enhanced PZE conditions were followed by blooms of phytoplankton, as demonstrated by the increase in algal-derived biomarker (i.e. pristane, phytane and the C19 n-alkane) concentrations and compound-specific isotopes. These observations confirm that palaeoenvironmental conditions were similar to those reported for the Permian/Triassic and Triassic/Jurassic mass extinction events. The sterane distributions varied across the three formations reflecting possible changes in the phytoplanktonic communities through time. Although a rise in atmospheric oxygen during the Cambrian has been previously associated with the rapid evolution of metazoans, the ecological challenges related to widespread anoxia must have had a major influence on the evolution of life in Cambrian oceans

Assessing the role of bitumen in the formation of stratabound Cu-(Ag) deposits: Insights from the Lorena deposit, Las Luces district, northern Chile

Stratabound Cu-(Ag) deposits located in north-central Chile have been grouped into two NS parallel belts according to the age of their volcanic and volcanoclastic host rocks. Deposits from the Cretaceous belt are characterized by an unusual assemblage of Cu sulfides with migrated hydrocarbons, whereas the presence of organic matter has not yet been recognized in deposits from the Jurassic belt. Here we report the first evidence of pyrobitumen in a Jurassic stratabound Cu-(Ag) deposit and evaluate its role in ore formation. We present a micro-analytical study of pyrobitumen associated with Cu-(Fe) sulfides in the Lorena deposit, located in northern Chile. Our approach involved a combination of surface and drill core sample characterization, (FE)-SEM observations, EMPA and mu-XRF mapping of pyrobitumen. In addition, we determined the speciation of sulfur in pyrobitumen by using synchrotron mu-XANES. Two main events of hypogene mineralization were identified at Lorena deposit, i.e., a pre-ore and a main Cu ore stage. The pre-ore stage is characterized by globularly-shaped pyrobitumen and minor pyrite, and a widespread albite alteration of the andesite host rock. Pre-ore pyrite was replaced by chalcopyrite, bornite and chalcocite, providing evidence for a late Cu inception. In the main Cu ore stage, chalcocite is often associated with sharp-edged, angular pyrobitumen, most likely indicating re mobilization or a later pulse of hydrocarbons. EMPA data show that pyrobitumen at Lorena is enriched in Fe (0.02-1.74 wt%), Cu (0.02-0.87 wt%), S (0.01-0.43 wt%) and Cl (0.01-0.4 wt%). Other elements detected include V, Co, Ni, Cr, Sb, As, Ag and Au. Both Ag and Au were only detected in a few spots, with Au reaching up to 600 ppm. Desktop and synchrotron mu-XRF mapping shows that S is homogeneously distributed within pyrobitumen, with lower S concentrations observed at grain rims. On the other hand, EMPA-WDS X-ray maps show that Cu precipitated on pyrobitumen grain surfaces, filling fractures and forming veinlets. In addition, textures showing the presence of micro-to nano-sized pyrobitumen inclusions within both pre-ore pyrite and main ore chalcocite grains point, unequivocally, to the interaction of hydrothermal fluids with hydrocarbons during the formation of this deposit. The high S concentrations measured in pyrobitumen and the presence of organosulfur compounds detected by mu-XANES can be attributed to an organic source. The pre-ore assemblage is interpreted as formed from a petroleum-aqueous fluid (connate waters?) mixture that migrated from the sedimentary source rock into the Jurassic host rocks where pyrite and pyrobitumen precipitated in the andesite. Late Cu-bearing hydrothermal fluids interacted with this pyrobitumen-pyrite assemblage to form Cu sulfides, either by replacement of pyrite or precipitation. We conclude that some of the S contained in pyrobitumen could have been released during interaction with the Cu-bearing hydrothermal fluid contributing, at least partially, to the S budget required for sulfide mineralization in the main ore stage. Our results provide evidence supporting pyrobitumen-fluid interaction as a key process in the formation of the Lorena deposit and possibly other stratabound Cu-(Ag) deposits in Chile.Millennium Science Initiative (MSI) through "Millennium Nucleus for Metal Tracing Along Subduction" grant Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1140780 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDAP 15090013 LNLS -Brazilian Synchrotron Light Laboratory, CNPEM/MCTIC FONDEQUIP project EQM150101 Society of Economic Geologists Foundation (SEGF) CNPEM ANID 2117138

Synthesis and biological evaluation of 3-amino-1,2,4-triazole derivatives as potential anticancer compounds

International audienceTwo series of compounds carrying 3-amino-1,2,4-triazole scaffold were synthesized and evaluated for their anticancer activity against a panel of cancer cell lines using XTT assay. The 1,2,4-triazole synthesis was revisited for the first series of pyridyl derivatives. The biological results revealed the efficiency of the 3-amino-1,2,4triazole core that could not be replaced and a clear beneficial effect of a 3-bromophenylamino moiety in position 3 of the triazole for both series (compounds 2.6 and 4.6) on several cell lines tested. Moreover, our results point out an antiangiogenic activity of these compounds. Overall, the 5-aryl-3-phenylamino-1,2,4-triazole structure has promising dual anticancer activity

Soluble forms of PD-L1 and PD-1 as prognostic and predictive markers of sunitinib efficacy in patients with metastatic clear cell renal cell carcinoma

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Diel fluctuations in solute distributions and biogeochemical cycling in a hypersaline microbial mat from Shark Bay,WA

Studying modern microbial mats can provide insights into how microbial communities interact with biogeochemical cycles. High-resolution, two-dimensional distributions of porewater analytes were determined in the upper three layers of a modern microbial mat from Nilemah, Shark Bay, Western Australia, using colorimetric diffusive equilibration in thin film (DET) and diffusive gradients in thin film (DGT) techniques. The colorimetric DET and DGT techniques were used to investigate the co-distributions of sulfide, iron(II), and phosphate and the alkalinity. Two-dimensional distributions of sulfide, iron(II) and phosphate showed a high degree of spatial heterogeneity under both light and dark conditions. However, average concentration profiles showed a clear shift in overall redox conditions between light and dark conditions. During light deployments, iron(II) and sulfide concentrations were generally low throughout the entire microbial mat. In contrast, during dark deployments, when anoxic conditions prevailed, higher concentrations of iron(II) and sulfide were observed and the sulfide boundary migrated towards the upper layer of the mat. Similar to the iron(II) profile, the phosphate profile showed an increase in concentration at night, suggesting that phosphate was released through the dissolution of iron–phosphate complexes under anoxic conditions.However, two-dimensional distributions revealed that hot spots of phosphate and iron(II) did not coincide, suggesting that porewater phosphate was mainly regulated by diel metabolic changes in the mat. Alkalinity profiles also demonstrated an increase in concentration at night, probably related to high rates of sulfate reduction under dark conditions. Complimentary microelectrode measurements of oxygen and sulfide confirmed that light-limited microbial communities play a significant role in regulating porewater solute concentrations, especially through photosynthetic activity that supports rapid re-oxidation of sulfide during the day. Sulfide was not detected in the upper layers (ca. 4 mm) of the mat by microelectrode measurements, but was found at those depths by the time-integratedDGT measurements. Complimentary silver foil deployments also showed a 2D distribution of sulfate-reducing activity occurring under oxic conditions in the top layers. DGT, O2 and sulfide microelectrode profiles and silver foils confirmed hotspots of sulfide production coinciding with cyanobacterial photosynthesis. Two-dimensional porewater analyte distributions showed significant small-scale heterogeneity, highlighting the complexity of such dynamic ecosystems and the advantage of two-dimensional methods

Plk1, upregulated by HIF-2, mediates metastasis and drug resistance of clear cell renal cell carcinoma

International audiencePolo-like kinase 1 (Plk1) expression is inversely correlated with survival advantages in many cancers. However, molecular mechanisms that underlie Plk1 expression are poorly understood. Here, we uncover a hypoxia-regulated mechanism of Plk1-mediated cancer metastasis and drug resistance. We demonstrated that a HIF-2-dependent regulatory pathway drives Plk1 expression in clear cell renal cell carcinoma (ccRCC). Mechanistically, HIF-2 transcriptionally targets the hypoxia response element of the Plk1 promoter. In ccRCC patients, high expression of Plk1 was correlated to poor disease-free survival and overall survival. Lossof-function of Plk1 in vivo markedly attenuated ccRCC growth and metastasis. High Plk1 expression conferred a resistant phenotype of ccRCC to targeted therapeutics such as sunitinib, in vitro, in vivo, and in metastatic ccRCC patients. Importantly, high Plk1 expression was defined in a subpopulation of ccRCC patients that are refractory to current therapies. Hence, we propose a therapeutic paradigm for improving outcomes of ccRCC patients