Sedimentary parameters control the sulfur isotope composition of marine pyrite.

Reconstructions of coupled carbon, oxygen, and sulfur cycles rely heavily on sedimentary pyrite sulfur isotope compositions (δ34Spyr). With a model of sediment diagenesis, paired with global datasets of sedimentary parameters, we show that the wide range of δ34Spyr (~100 per mil) in modern marine sediments arises from geographic patterns in the relative rates of diffusion, burial, and microbial reduction of sulfate. By contrast, the microbial sulfur isotope fractionation remains large and relatively uniform. Over Earth history, the effect of increasing seawater sulfate and oxygen concentrations on sulfate and sulfide transport and reaction may explain the corresponding increase observed in the δ34S offset between sulfate and pyrite. More subtle variations may be related to changes in depositional environments associated with sea level fluctuations and supercontinent cycles.

Deconvolving microbial and environmental controls on marine sedimentary pyrite sulfur isotope ratios.

Reconstructions of past environmental conditions and biological activity are often based on bulk stable isotope proxies, which are inherently open to multiple interpretations. This is particularly true of the sulfur isotopic composition of sedimentary pyrite (δ34Spyr), which is used to reconstruct ocean-atmosphere oxidation state and track the evolution of several microbial metabolic pathways. We present a microanalytical approach to deconvolving the multiple signals that influence δ34Spyr, yielding both the unambiguous determination of microbial isotopic fractionation (εmic) and new information about depositional conditions. We applied this approach to recent glacial-interglacial sediments, which feature over 70‰ variations in bulk δ34Spyr across these environmental transitions. Despite profound environmental change, εmic remained essentially invariant throughout this interval and the observed range in δ34Spyr was instead driven by climate-induced variations in sedimentation.

Strong local, not global, controls on marine pyrite sulfur isotopes.

Understanding variation in the sulfur isotopic composition of sedimentary pyrite (δ34Spyr) is motivated by the key role of sulfur biogeochemistry in regulating Earth's surface oxidation state. Until recently, the impact of local depositional conditions on δ34Spyr has remained underappreciated, and stratigraphic variations in δ34Spyr were interpreted mostly to reflect global changes in biogeochemical cycling. We present two coeval δ34Spyr records from shelf and basin settings in a single sedimentary system. Despite their proximity and contemporaneous deposition, these two records preserve radically different geochemical signals. Swings of ~65‰ in shelf δ34Spyr track short-term variations in local sedimentation and are completely absent from the abyssal record. In contrast, a long-term ~30‰ decrease in abyssal δ34Spyr reflects regional changes in ocean circulation and/or sustained pyrite formation. These results highlight strong local controls on δ34Spyr, calling for reevaluation of the current practice of using δ34Spyr stratigraphic variations to infer global changes in Earth's surface environment.

Direct Observation of the Dynamics of Single-Cell Metabolic Activity during Microbial Diauxic Growth.

Population-level analyses are rapidly becoming inadequate to answer many of biomedical science and microbial ecology's most pressing questions. The role of microbial populations within ecosystems and the evolutionary selective pressure on individuals depend fundamentally on the metabolic activity of single cells. Yet, many existing single-cell technologies provide only indirect evidence of metabolic specialization because they rely on correlations between transcription and phenotype established at the level of the population to infer activity. In this study, we take a top-down approach using isotope labels and secondary ion mass spectrometry to track the uptake of carbon and nitrogen atoms from different sources into biomass and directly observe dynamic changes in anabolic specialization at the level of single cells. We investigate the classic microbiological phenomenon of diauxic growth at the single-cell level in the model methylotroph Methylobacterium extorquens In nature, this organism inhabits the phyllosphere, where it experiences diurnal changes in the available carbon substrates, necessitating an overhaul of central carbon metabolism. We show that the population exhibits a unimodal response to the changing availability of viable substrates, a conclusion that supports the canonical model but has thus far been supported by only indirect evidence. We anticipate that the ability to monitor the dynamics of anabolism in individual cells directly will have important applications across the fields of ecology, medicine, and biogeochemistry, especially where regulation downstream of transcription has the potential to manifest as heterogeneity that would be undetectable with other existing single-cell approaches.IMPORTANCE Understanding how genetic information is realized as the behavior of individual cells is a long-term goal of biology but represents a significant technological challenge. In clonal microbial populations, variation in gene regulation is often interpreted as metabolic heterogeneity. This follows the central dogma of biology, in which information flows from DNA to RNA to protein and ultimately manifests as activity. At present, DNA and RNA can be characterized in single cells, but the abundance and activity of proteins cannot. Inferences about metabolic activity usually therefore rely on the assumption that transcription reflects activity. By tracking the atoms from which they build their biomass, we make direct observations of growth rate and substrate specialization in individual cells throughout a period of growth in a changing environment. This approach allows the flow of information from DNA to be constrained from the distal end of the regulatory cascade and will become an essential tool in the rapidly advancing field of single-cell metabolism.

Environmental insights from high-resolution (SIMS) sulfur isotope analyses of sulfides in Proterozoic microbialites with diverse mat textures.

In modern microbial mats, hydrogen sulfide shows pronounced sulfur isotope (δ34 S) variability over small spatial scales (~50‰ over <4 mm), providing information about microbial sulfur cycling within different ecological niches in the mat. In the geological record, the location of pyrite formation, overprinting from mat accretion, and post-depositional alteration also affect both fine-scale δ34 S patterns and bulk δ34 Spyrite values. We report µm-scale δ34 S patterns in Proterozoic samples with well-preserved microbial mat textures. We show a well-defined relationship between δ34 S values and sulfide mineral grain size and type. Small pyrite grains (<25 µm) span a large range, tending toward high δ34 S values (-54.5‰ to 11.7‰, mean: -14.4‰). Larger pyrite grains (>25 µm) have low but equally variable δ34 S values (-61.0‰ to -10.5‰, mean: -44.4‰). In one sample, larger sphalerite grains (>35 µm) have intermediate and essentially invariant δ34 S values (-22.6‰ to -15.6‰, mean: -19.4‰). We suggest that different sulfide mineral populations reflect separate stages of formation. In the first stage, small pyrite grains form near the mat surface along a redox boundary where high rates of sulfate reduction, partial closed-system sulfate consumption in microenvironments, and/or sulfide oxidation lead to high δ34 S values. In another stage, large sphalerite grains with low δ34 S values grow along the edges of pore spaces formed from desiccation of the mat. Large pyrite grains form deeper in the mat at slower sulfate reduction rates, leading to low δ34 Ssulfide values. We do not see evidence for significant 34 S-enrichment in bulk pore water sulfide at depth in the mat due to closed-system Rayleigh fractionation effects. On a local scale, Rayleigh fractionation influences the range of δ34 S values measured for individual pyrite grains. Fine-scale analyses of δ34 Spyrite patterns can thus be used to extract environmental information from ancient microbial mats and aid in the interpretation of bulk δ34 Spyrite records.

Sulphur cycling in a Neoarchaean microbial mat.

Multiple sulphur (S) isotope ratios are powerful proxies to understand the complexity of S biogeochemical cycling through Deep Time. The disappearance of a sulphur mass-independent fractionation (S-MIF) signal in rocks <~2.4 Ga has been used to date a dramatic rise in atmospheric oxygen levels. However, intricacies of the S-cycle before the Great Oxidation Event remain poorly understood. For example, the isotope composition of coeval atmospherically derived sulphur species is still debated. Furthermore, variation in Archaean pyrite δ34 S values has been widely attributed to microbial sulphate reduction (MSR). While petrographic evidence for Archaean early-diagenetic pyrite formation is common, textural evidence for the presence and distribution of MSR remains enigmatic. We combined detailed petrographic and in situ, high-resolution multiple S-isotope studies (δ34 S and Δ33 S) using secondary ion mass spectrometry (SIMS) to document the S-isotope signatures of exceptionally well-preserved, pyritised microbialites in shales from the ~2.65-Ga Lokammona Formation, Ghaap Group, South Africa. The presence of MSR in this Neoarchaean microbial mat is supported by typical biogenic textures including wavy crinkled laminae, and early-diagenetic pyrite containing <26‰ µm-scale variations in δ34 S and Δ33 S = -0.21 ± 0.65‰ (±1σ). These large variations in δ34 S values suggest Rayleigh distillation of a limited sulphate pool during high rates of MSR. Furthermore, we identified a second, morphologically distinct pyrite phase that precipitated after lithification, with δ34 S = 8.36 ± 1.16‰ and Δ33 S = 5.54 ± 1.53‰ (±1σ). We propose that the S-MIF signature of this secondary pyrite does not reflect contemporaneous atmospheric processes at the time of deposition; instead, it formed by the influx of later-stage sulphur-bearing fluids containing an inherited atmospheric S-MIF signal and/or from magnetic isotope effects during thermochemical sulphate reduction. These insights highlight the complementary nature of petrography and SIMS studies to resolve multigenerational pyrite formation pathways in the geological record.

"The Pain of Exile": What Social Workers Need to Know about Burmese Refugees.

Refugees from Burma have comprised the largest group of refugees resettling in the United States over the past decade, with nearly 90,000 people, and 19 percent of the total refugee population. However, very little literature exists that describes the cultural context and displacement experiences of this population. This article addresses that gap in the literature by examining historical, social, political, and cultural dimensions relevant to social work practice with Burmese refugees. Practice with Burmese refugees should be informed by knowledge of refugee policy, refugee resettlement, and social services delivery systems; the Burmese historical and political context; the community's specific strengths, needs, and cultural diversity; and human rights and social justice issues. Strong community partnerships between social workers and indigenous community leaders, between resettlement agencies and ethnic community-based organizations, and between different Burmese refugee groups are important to meeting short- and long-term social services needs and fostering successful adaptation and community integration.

Thiosulfate oxidation by Thiomicrospira thermophila: metabolic flexibility in response to ambient geochemistry.

Previous studies of the stoichiometry of thiosulfate oxidation by colorless sulfur bacteria have failed to demonstrate mass balance of sulfur, indicating that unidentified oxidized products must be present. Here the reaction stoichiometry and kinetics under variable pH conditions during the growth of Thiomicrospira thermophila strain EPR85, isolated from diffuse hydrothermal fluids at the East Pacific Rise, is presented. At pH 8.0, thiosulfate was stoichiometrically converted to sulfate. At lower pH, the products of thiosulfate oxidation were extracellular elemental sulfur and sulfate. We were able to replicate previous experiments and identify the missing sulfur as tetrathionate, consistent with previous reports of the activity of thiosulfate dehydrogenase. Tetrathionate was formed under slightly acidic conditions. Genomic DNA from T. thermophila strain EPR85 contains genes homologous to those in the Sox pathway (soxAXYZBCDL), as well as rhodanese and thiosulfate dehydrogenase. No other sulfur oxidizing bacteria containing sox(CD)2 genes have been reported to produce extracellular elemental sulfur. If the apparent modified Sox pathway we observed in T. thermophila is present in marine Thiobacillus and Thiomicrospira species, production of extracellular elemental sulfur may be biogeochemically important in marine sulfur cycling.

Spatial variability in photosynthetic and heterotrophic activity drives localized δ13C org fluctuations and carbonate precipitation in hypersaline microbial mats.

Modern laminated photosynthetic microbial mats are ideal environments to study how microbial activity creates and modifies carbon and sulfur isotopic signatures prior to lithification. Laminated microbial mats from a hypersaline lagoon (Guerrero Negro, Baja California, Mexico) maintained in a flume in a greenhouse at NASA Ames Research Center were sampled for δ(13) C of organic material and carbonate to assess the impact of carbon fixation (e.g., photosynthesis) and decomposition (e.g., bacterial respiration) on δ(13) C signatures. In the photic zone, the δ(13) C org signature records a complex relationship between the activities of cyanobacteria under variable conditions of CO2 limitation with a significant contribution from green sulfur bacteria using the reductive TCA cycle for carbon fixation. Carbonate is present in some layers of the mat, associated with high concentrations of bacteriochlorophyll e (characteristic of green sulfur bacteria) and exhibits δ(13) C signatures similar to DIC in the overlying water column (-2.0‰), with small but variable decreases consistent with localized heterotrophic activity from sulfate-reducing bacteria (SRB). Model results indicate respiration rates in the upper 12 mm of the mat alter in situ pH and HCO3- concentrations to create both phototrophic CO2 limitation and carbonate supersaturation, leading to local precipitation of carbonate minerals. The measured activity of SRB with depth suggests they variably contribute to decomposition in the mat dependent on organic substrate concentrations. Millimeter-scale variability in the δ(13) C org signature beneath the photic zone in the mat is a result of shifting dominance between cyanobacteria and green sulfur bacteria with the aggregate signature overprinted by heterotrophic reworking by SRB and methanogens. These observations highlight the impact of sedimentary microbial processes on δ(13) C org signatures; these processes need to be considered when attempting to relate observed isotopic signatures in ancient sedimentary strata to conditions in the overlying water column at the time of deposition and associated inferences about carbon cycling.

Carbon isotopes and lipid biomarkers from organic-rich facies of the Shuram Formation, Sultanate of Oman.

The largest recorded carbon isotopic excursion in Earth history is observed globally in carbonate rocks of middle Ediacaran age. Known from the Sultanate of Oman as the 'Shuram excursion', this event records a dramatic, systematic shift in δ(13) Ccarbonate values to ca. -12‰. Attempts to explain the nature, magnitude and origin of this excursion include (i) a primary signal resulting from the protracted oxidation of a large dissolved organic carbon reservoir in seawater, release of methane from sediment-hosted clathrates, or water column stratification; and (ii) a secondary signal from diagenetic processes. The compositions and isotope ratios of organic carbon phases during the excursion are critical to evaluating these ideas; however, previous work has focused on localities that are low in organic carbon, hindering straightforward interpretation of the observed time-series trends. We report carbon isotope data from bulk organic carbon, extracted bitumen and kerogen, in addition to lipid biomarker data, from a subsurface well drilled on the eastern flank of the South Oman Salt Basin, Sultanate of Oman. This section captures Nafun Group strata through the Ediacaran-Cambrian boundary in the Ara Group and includes an organic-rich, deeper-water facies of the Shuram Formation. Despite the high organic matter contents, the carbon isotopic compositions of carbonates - which record a negative δ(13) C isotope excursion similar in shape and magnitude to sections elsewhere in Oman - do not covary with those of organic phases (bulk TOC, bitumen and kerogen). Paired inorganic and organic δ(13) C data only display coupled behaviour during the latter part of the excursion's recovery. Furthermore, lipid biomarker data reveal that organic matter composition and source inputs varied stratigraphically, reflecting biological community shifts in non-migrated, syngenetic organic matter deposited during this interval.

Oxidation of the Ediacaran ocean.

Oxygenation of the Earth's surface is increasingly thought to have occurred in two steps. The first step, which occurred approximately 2,300 million years (Myr) ago, involved a significant increase in atmospheric oxygen concentrations and oxygenation of the surface ocean. A further increase in atmospheric oxygen appears to have taken place during the late Neoproterozoic period ( approximately 800-542 Myr ago). This increase may have stimulated the evolution of macroscopic multicellular animals and the subsequent radiation of calcified invertebrates, and may have led to oxygenation of the deep ocean. However, the nature and timing of Neoproterozoic oxidation remain uncertain. Here we present high-resolution carbon isotope and sulphur isotope records from the Huqf Supergroup, Sultanate of Oman, that cover most of the Ediacaran period (approximately 635 to approximately 548 Myr ago). These records indicate that the ocean became increasingly oxygenated after the end of the Marinoan glaciation, and they allow us to identify three distinct stages of oxidation. When considered in the context of other records from this period, our data indicate that certain groups of eukaryotic organisms appeared and diversified during the second and third stages of oxygenation. The second stage corresponds with the Shuram excursion in the carbon isotope record and seems to have involved the oxidation of a large reservoir of organic carbon suspended in the deep ocean, indicating that this event may have had a key role in the evolution of eukaryotic organisms. Our data thus provide new insights into the oxygenation of the Ediacaran ocean and the stepwise restructuring of the carbon and sulphur cycles that occurred during this significant period of Earth's history.

Aeolian processes at the Mars Exploration Rover Meridiani Planum landing site.

The martian surface is a natural laboratory for testing our understanding of the physics of aeolian (wind-related) processes in an environment different from that of Earth. Martian surface markings and atmospheric opacity are time-variable, indicating that fine particles at the surface are mobilized regularly by wind. Regolith (unconsolidated surface material) at the Mars Exploration Rover Opportunity's landing site has been affected greatly by wind, which has created and reoriented bedforms, sorted grains, and eroded bedrock. Aeolian features here preserve a unique record of changing wind direction and wind strength. Here we present an in situ examination of a martian bright wind streak, which provides evidence consistent with a previously proposed formational model for such features. We also show that a widely used criterion for distinguishing between aeolian saltation- and suspension-dominated grain behaviour is different on Mars, and that estimated wind friction speeds between 2 and 3 m s(-1), most recently from the northwest, are associated with recent global dust storms, providing ground truth for climate model predictions.

Soils of Eagle crater and Meridiani Planum at the Opportunity Rover landing site.

The soils at the Opportunity site are fine-grained basaltic sands mixed with dust and sulfate-rich outcrop debris. Hematite is concentrated in spherules eroded from the strata. Ongoing saltation exhumes the spherules and their fragments, concentrating them at the surface. Spherules emerge from soils coated, perhaps from subsurface cementation, by salts. Two types of vesicular clasts may represent basaltic sand sources. Eolian ripples, armored by well-sorted hematite-rich grains, pervade Meridiani Planum. The thickness of the soil on the plain is estimated to be about a meter. The flatness and thin cover suggest that the plain may represent the original sedimentary surface.

Thrombolytic fibrin specificity influences activated partial thromboplastin time prolongation in vitro.

Despite limited comparative data, guidelines suggest the same concomitant unfractionated heparin (UFH) dose for all fibrin-specific thrombolytic agents in acute myocardial infarction. Since a supratherapeutic activated partial thromboplastin time (aPTT) correlates with adverse outcomes, clarifying effects of various agents on aPTT are needed. The present in vitro study evaluated the influence of alteplase (rt-PA), reteplase (r-PA), and tenecteplase (TNK) on aPTT prolongation. Blood samples from healthy volunteers (n = 12) were treated with equipotent concentrations of rt-PA, r-PA, and TNK, with and without UFH. Samples of each treatment group were incubated at 37 degrees C; aPTT and fibrinogen activity were measured after 4 h. Mean aPTT values for rt-PA alone and r-PA alone were prolonged versus those of TNK alone (P = 0.001 for both). Combined with UFH, rt-PA and r-PA increased the aPTT versus UFH alone (P < 0.05 for both). Interestingly, TNK + UFH reduced the aPTT versus UFH alone (P < 0.001). A negative correlation existed between fibrinogen activity and aPTT for all treatments, except TNK alone. The present investigation illustrates that an agent with maximal fibrin specificity (TNK) has minimal effect on the aPTT, while agents with less fibrin specificity are more likely to prolong the aPTT, with and without UFH present.

Continuous subcutaneous infusion practices of United States hospices.

In hospice organizations, continuous subcutaneous infusion (CSI) is a common medication delivery modality for pain management. Nonetheless, little is known regarding the practices of hospice organizations in their utilization of this technique. We surveyed 3,930 hospice organizations to describe indication, diluents, medications, and other variable factors associated with CSI utilization. Of the 3,930 surveys sent, 907 were returned, yielding a response rate of 24%. Seventy-three percent of hospice organizations surveyed indicated they utilized CSI. The average daily census (ADC) of these hospices was 38.6 +/- 61.0. The most common indication for CSI use was palliative management (95%). The most common medication used in CSI was morphine sulfate (97%). These results indicate that CSI utilization may be widespread in hospices and further study regarding this delivery system is warranted.

Pharmacy student training in United States hospices.

Hospice is a quickly growing field in health care in the United States. As the pharmacist's role in providing patient care to persons at the end of life increases, considerations should be given for training pharmacy students in this area. The objectives of this study were to examine the frequency of pharmacy student education and training among United States hospice organizations as well as to describe factors of hospice organizations that are associated with pharmacy student training. This is the first study of which we are aware to address the availability of experiential rotations for pharmacy students in hospice programs. A one-page questionnaire was mailed to 3,762 hospice organizations with addresses obtained from the National Hospice and Palliative Care Organization (NHPCO). Following two mailings, eight weeks apart, 907 responses were obtained. Ninety-four (10 percent) hospices trained pharmacy students, 246 (27 percent) trained medical students, 357 (39 percent) trained social work students, and 623 (69 percent) trained nursing students. These results indicate that the experiential training needs of United States pharmacy students are being addressed. However, further study is warranted to describe the various experiences of pharmacy students within the hospice setting.

Effects of a colostrum replacement product derived from serum on immunoglobulin G absorption by calves.

Calves are born hypogammaglobulinemic and rely on immunoglobulin (Ig) from colostrum to obtain passive immunity. Previous research has indicated that colostrum supplements derived from milk are less effective than is maternal colostrum in providing adequate IgG to neonatal calves. Our objective was to determine the absorption of IgG by newborn calves fed a USDA food-grade colostrum supplement derived from bovine serum or fed pooled maternal colostrum. Holstein calves (n = 20; 10 bulls) were removed from the dam within 1 h of birth and were housed in individual stalls for the 24-h study. Calves were fed 2 L of colostrum or colostrum replacer at 1.5 and 13.5 h (+/- 0.1 h). Calves were blocked by colostrum pool, and replacer was fed to provide equal intakes of IgG within blocks. Jugular blood was collected at 1 and 24 h (+/- 0.1 h) for analysis of IgG by radial immunodiffusion. At 24 h, calves were injected with 1.5 ml of Evans blue dye to estimate plasma volume. Mean plasma IgG at 24 h of age was 7.3 +/- 0.4 g/L and was affected by an interaction of block and treatment. Apparent efficiency of IgG absorption of 24 h was reduced when 750 g of the colostrum replacement product were fed but was increased when 266 g of colostrum replacement product were fed. Mean plasma volume was unaffected by treatment and was 3.5 +/- 0.2 L or 9.1% of BW. These data indicate that efficiency of IgG absorption from the colostrum replacement product may be affected by amount of material fed. Proteins other than IgG in the colostrum replacement product might have reduced the efficiency of IgG absorption.