Identifying Sulfate Sources and Recycling Processes in the Atacama Desert with Sulfur, Strontium and Triple Oxygen Isotopes

Sulfate is the dominating salt in soils of the Atacama Desert, one of the oldest and driest deserts on Earth. Sulfate sources include marine sulfate, terrestrial weathering (e.g., redistribution of surface material), and sulfate that is formed within the atmosphere by oxidation of reduced sulfur species. The stable isotopic composition of sulfate (D17OSO4 , d18OSO4 , and d34SSO4) is characteristic for each formation process, wherefore it serves as a tool to identify respective sulfate sources. The classical stable isotope proxies (d18OSO4 and d34SSO4) mainly help to distinguish between marine and terrestrial sulfate. In addition to these, the novel triple oxygen isotope tool (D17OSO4) also allows to identify sulfate formed in the atmosphere. Under Earth’s surface conditions, the isotopic composition of sulfate only alters when the sulfate is processed by microbes or plants. Hence, the isotopic composition of sulfate allows identifying the sulfate sources and enables to draw conclusions on biological alteration processes. This is especially interesting for areas, where biological activity is limited due to the low water availability, like the Atacama Desert. The first study presents a fast and easy to use method to determine D17OSO4 of natural sulfate samples. It includes a protocol for the quantitative dissolution of natural Ca- and Na-sulfates samples and subsequent conversion into sufficiently pure Ag-sulfate for pyrolysis analyses. Determined D17OSO4 values from multiple in-house standards are compared to previously published results from different laboratories using different methods (pyrolysis and fluorination). A normalization procedure results in excellent reproducibility of standards, comparable to other laboratories including those using those using the fluorination method, verifying the accuracy and precision of the presented method. The second study aims to improve the understanding of sulfate deposition and the spatial distribution of hyperaridity. Samples taken along four E-W transects are analyzed for their isotopic compositions (D17OSO4 , d18OSO4 , d34SSO4 , and 86Sr/88Sr). Throughout positive D17OSO4 values, determined using the method developed in the first study, suggest a significant contribution from atmospheric sulfate for all Atacama Desert sediments. The combination of D17OSO4 and d34SSO4 allows distinguishing between marine sulfate and sulfate that derived from atmospheric oxidation of biogenic sulfur gases emitted from the Ocean. In addition, a clear trend is visible in the triple oxygen isotopic composition (D17OSO4 and d18OSO4) of all samples, pointing from the isotopic composition of atmospheric sulfate to that of biological cycled sulfate. This trend reflects a gradient in the degree of biological activity and can therefore be used as indicator for water availability in the Atacama Desert. This work provides an optimized pyrolysis method for triple oxygen isotope analysis of sulfate from desert environments and expands our knowledge of sulfate source contribution, sulfate deposition, biological sulfate cycling, and water availability within the hyperarid Atacama Desert

THE ROLE OF OOCYTE-ENRICHED TCL1 FAMILY IN IPSC REPROGRAMMING

Ph.DDOCTOR OF PHILOSOPH

Non-Targeted Metabolite Profiling Reveals Host Metabolomic Reprogramming during the Interaction of Black Pepper with Phytophthora capsici

Phytophthora capsici is one of the most destructive pathogens causing quick wilt (foot rot) disease in black pepper (Piper nigrum L.) to which no effective resistance has been defined. To better understand the P. nigrum–P. capsici pathosystem, we employed metabolomic approaches based on flow‐infusion electrospray–high‐resolution mass spectrometry. Changes in the leaf metabolome were assessed in infected and systemic tissues at 24 and 48 hpi. Principal Component Analysis of the derived data indicated that the infected leaves showed a rapid metabolic response by 24 hpi whereas the systemic leaves took 48 hpi to respond to the infection. The major sources of variations between infected leaf and systemic leaf were identified, and enrichment pathway analysis indicated, major shifts in amino acid, tricarboxylic acid cycle, nucleotide and vitamin B6 metabolism upon infection. Moreover, the individual metabolites involved in defensive phytohormone signalling were identified. RT‐qPCR analysis of key salicylate and jasmonate biosynthetic genes indicated a transient reduction of expression at 24 hpi but this increased subsequently. Exogenous application of jasmonate and salicylate reduced P. capsici disease symptoms, but this effect was suppressed with the co‐application of abscisic acid. The results are consistent with abscisic acid reprogramming, salicylate and jasmonate defences in infected leaves to facilitate the formation of disease. The augmentation of salicylate and jasmonate defences could represent an approach through which quick wilt disease could be controlled in black pepper

Infection prevention and control interventions in the first outbreak of methicillin-resistant Staphylococcus aureus infections in an equine hospital in Sweden

<p>Abstract</p> <p>Background</p> <p>The first outbreak of methicillin-resistant <it>Staphylococcus aureus </it>(MRSA) infection in horses in Sweden occurred in 2008 at the University Animal Hospital and highlighted the need for improved infection prevention and control. The present study describes interventions and infection prevention control in an equine hospital setting July 2008 - April 2010.</p> <p>Method</p> <p>This descriptive study of interventions is based on examination of policy documents, medical records, notes from meetings and cost estimates. MRSA cases were identified through clinical sampling and telephone enquiries about horses post-surgery. Prospective sampling in the hospital environment with culture for MRSA and genotyping of isolates by <it>spa</it>-typing and pulsed-field gel electrophoresis (PFGE) were performed.</p> <p>Results</p> <p>Interventions focused on interruption of indirect contact spread of MRSA between horses via staff and equipment and included: Temporary suspension of elective surgery; and identification and isolation of MRSA-infected horses; collaboration was initiated between authorities in animal and human public health, human medicine infection control and the veterinary hospital; extensive cleaning and disinfection was performed; basic hygiene and cleaning policies, staff training, equipment modification and interior renovation were implemented over seven months.</p> <p>Ten (11%) of 92 surfaces sampled between July 2008 and April 2010 tested positive for MRSA <it>spa</it>-type 011, seven of which were from the first of nine sampling occasions. PFGE typing showed the isolates to be the outbreak strain (9 of 10) or a closely related strain. Two new cases of MRSA infection occurred 14 and 19 months later, but had no proven connections to the outbreak cases.</p> <p>Conclusions</p> <p>Collaboration between relevant authorities and the veterinary hospital and formation of an infection control committee with an executive working group were required to move the intervention process forward. Support from hospital management and the dedication of staff were essential for the development and implementation of new, improved routines. Demonstration of the outbreak strain in the environment was useful for interventions such as improvement of cleaning routines and interior design, and increased compliance with basic hygienic precautions. The interventions led to a reduction in MRSA-positive samples and the outbreak was considered curbed as no new cases occurred for over a year.</p

Conserved Regulation of p53 Network Dosage by MicroRNA–125b Occurs through Evolving miRNA–Target Gene Pairs

MicroRNAs regulate networks of genes to orchestrate cellular functions. MiR-125b, the vertebrate homologue of the Caenorhabditis elegans microRNA lin-4, has been implicated in the regulation of neural and hematopoietic stem cell homeostasis, analogous to how lin-4 regulates stem cells in C. elegans. Depending on the cell context, miR-125b has been proposed to regulate both apoptosis and proliferation. Because the p53 network is a central regulator of both apoptosis and proliferation, the dual roles of miR-125b raise the question of what genes in the p53 network might be regulated by miR-125b. By using a gain- and loss-of-function screen for miR-125b targets in humans, mice, and zebrafish and by validating these targets with the luciferase assay and a novel miRNA pull-down assay, we demonstrate that miR-125b directly represses 20 novel targets in the p53 network. These targets include both apoptosis regulators like Bak1, Igfbp3, Itch, Puma, Prkra, Tp53inp1, Tp53, Zac1, and also cell-cycle regulators like cyclin C, Cdc25c, Cdkn2c, Edn1, Ppp1ca, Sel1l, in the p53 network. We found that, although each miRNA–target pair was seldom conserved, miR-125b regulation of the p53 pathway is conserved at the network level. Our results lead us to propose that miR-125b buffers and fine-tunes p53 network activity by regulating the dose of both proliferative and apoptotic regulators, with implications for tissue stem cell homeostasis and oncogenesis

The hyperarid core of the Atacama Desert

International audienceThe Atacama Desert is one of the driest regions on Earth, characterized by long-term hyperarid climate. However, there are regional gradients from hyperarid to arid conditions. Today, the hyperarid core, the area receiving less than 2 mm•a −1 precipitation, is situated between 19 and 22˚S. In the past, regional climate changes caused local pluvial phases in the hyperarid Atacama and possibly shifted aridity gradients. We investigated the distribution of gypsum, nitrate and further water-soluble mineral phases along WE transects in the northern, central, and southern part of the Atacama Desert to identify correlations with the degree of aridity. The main mineral composition was determined by XRD analyses. Thermogravimetric analyses were used to quantify the gypsum content. Furthermore, samples were leached and leachates were analysed by ICP-OES and MTPR to identify water-soluble mineral phases. Water-soluble minerals are washed out during precipitation events. Thus, the presence of water-soluble minerals could be an indication for hyperaridity. Their concentrations are highest in the northern transect and very low in the southern area implying a higher degree of aridity in the northern part of the Atacama Desert. Gypsum contents show clear differences between surface and subsurface samples. Along the northern transect surface samples have continuously moderate gypsum contents. In the subsurface, gypsum is only present near the coast. In contrast, in the southern area high amounts of gypsum are common in surface as well as subsurface samples. These results confirm that water availability is lower in the northern part of the Atacama Desert, where only surface layers are hydrated, probably by sporadic fog events. In the southern area rare precipitation events provide enough water to hydrate deeper soil layers

The spatial distribution of soluble salts in the surface soil of the Atacama Desert and their relationship to hyperaridity

We systematically investigated the spatial distribution of sulfates, chlorides, and nitrates in Atacama Desert soils in order to identify their relationship to long-term aridity gradients and to secondary redistribution and phase transformation. Thin surface crusts, powdery surface material and subsurface concretions from up to 40 cm depth were sampled along several latitudinal transects between 19.5-25 degrees S and 68.5-70.5 degrees W. The samples were characterized by total soil chemical analysis (ICP-OES and spectrophotometric analysis) complemented by XRD and thermogravimetric analysis to determine contents of chloride, nitrate, and major elements along with gypsum and anhydrite abundance in Atacama Desert soils. Our results demonstrate that the spatial distribution of gypsum, anhydrite, halite, and nitrates in Atacama Desert soils is indeed linked to aridity gradients, but also sources, and secondary dissolution processes. Nitrates and chlorides are best preserved between 19 and 22 degrees S, which thus may constitute the long-term hyperarid core of the Atacama Desert. Remobilization within the soil is ubiquitous south of 22 degrees S, but generally also occurs on the debris fans prograding from the Precordillera into the Central Depression. A near-constant concentration ratio of Na/Cl = 0.83 - very similar to the sea water ratio - throughout the desert and concentration maxima within the reaches of coastal fog penetration below the altitude of 1200 m reveals that sea spray is the primary source of halite in Atacama Desert soils. Calcium sulfates dominate Atacama Desert soils. Deposition is primarily as gypsum, but anhydrite is abundant in the northern Central Depression between 19 and 22 degrees S. The apparent association of anhydrite with high concentrations of nitrate and chloride may point to a formation by dissolution and secondary reprecipitation from salt-concentrated fluids. The predominance of anhydrite in the Central Depression suggest geomorphology and water availability as additional factors remaining to be determined

Identifying Sulfate Sources and Water Availability using Triple Oxygen and Sulfur Isotopes

International audienc