A Machine-Learning Approach to Biosignature Exploration on Early Earth and Mars Using Sulfur Isotope and Trace Element Data in Pyrite.

We propose a novel approach to identify the origin of pyrite grains and distinguish biologically influenced sedimentary pyrite using combined sulfur isotope (δS) and trace element (TE) analyses. To classify and predict the origin of individual pyrite grains, we applied multiple machine-learning algorithms to coupled δS and TE data from pyrite grains formed from diverse sedimentary, hydrothermal, and metasomatic processes across geologic time. Our unsupervised classification algorithm, K-means++ cluster analysis, yielded six classes based on the formation environment of the pyrite: sedimentary, low temperature hydrothermal, medium temperature, polymetallic hydrothermal, high temperature, and large euhedral.

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 (δS), 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 δS, yielding both the unambiguous determination of microbial isotopic fractionation (ε) and new information about depositional conditions.

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 (δS). With a model of sediment diagenesis, paired with global datasets of sedimentary parameters, we show that the wide range of δS (~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.

Sedimentary pyrite sulfur isotope compositions preserve signatures of the surface microbial mat environment in sediments underlying low-oxygen cyanobacterial mats.

The sedimentary pyrite sulfur isotope (δ S) record is an archive of ancient microbial sulfur cycling and environmental conditions. Interpretations of pyrite δ S signatures in sediments deposited in microbial mat ecosystems are based on studies of modern microbial mat porewater sulfide δ S geochemistry. Pyrite δ S values often capture δ S signatures of porewater sulfide at the location of pyrite formation.

Evaluation of a mandatory theory-based physical activity course on motivation among predominantly Hispanic college students.

ObjectiveThe present study aims to examine the impacts of a mandatory physical activity (PA) course on exercise motivation among predominately Hispanic college students. The course was designed based on the Self-Determination Theory to increase students' PA motivation. A total of 383 college students (=126; =257; =19.

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

Understanding variation in the sulfur isotopic composition of sedimentary pyrite (δS) 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 δS has remained underappreciated, and stratigraphic variations in δS were interpreted mostly to reflect global changes in biogeochemical cycling. We present two coeval δS records from shelf and basin settings in a single sedimentary system.

Do the types and routes of proton pump inhibitor treatments affect in ICU patients? A retrospective cohort study.

: : Proton pump inhibitors (PPI) are associated with Clostridium difficile infection (CDI). Impact of the route of administration is unknown.: Patients in Multiparameter Intelligent Monitoring in Intensive Care II database (MIMIC-II) from 2001 to 2008, >18 years old, admitted to medical, surgical, or cardiac ICUs were included.

Mixotrophic chemosynthesis in a deep-sea anemone from hydrothermal vents in the Pescadero Basin, Gulf of California.

Background: Numerous deep-sea invertebrates, at both hydrothermal vents and methane seeps, have formed symbiotic associations with internal chemosynthetic bacteria in order to harness inorganic energy sources typically unavailable to animals. Despite success in nearly all marine habitats and their well-known associations with photosynthetic symbionts, Cnidaria remain one of the only phyla present in the deep-sea without a clearly documented example of dependence on chemosynthetic symbionts.

Results: A new chemosynthetic symbiosis between the sea anemone Ostiactis pearseae and intracellular bacteria was discovered at ~ 3700 m deep hydrothermal vents in the southern Pescadero Basin, Gulf of California.

Isotopic Fractionation Associated With Sulfate Import and Activation by str. Hildenborough.

The use of stable isotopes to trace biogeochemical sulfur cycling relies on an understanding of how isotopic fractionation is imposed by metabolic networks. We investigated the effects of the first two enzymatic steps in the dissimilatory sulfate reduction (DSR) network - sulfate permease and sulfate adenylyl transferase (Sat) - on the sulfur and oxygen isotopic composition of residual sulfate. Mutant strains of str.

Bioenergetic characterization of a shallow-sea hydrothermal vent system: Milos Island, Greece.

Shallow-sea hydrothermal systems, like their deep-sea and terrestrial counterparts, can serve as relatively accessible portals into the microbial ecology of subsurface environments. In this study, we determined the chemical composition of 47 sediment porewater samples along a transect from a diffuse shallow-sea hydrothermal vent to a non-thermal background area in Paleochori Bay, Milos Island, Greece. These geochemical data were combined with thermodynamic calculations to quantify potential sources of energy that may support in situ chemolithotrophy.

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.

Trace Element Concentrations in Hydrothermal Silica Deposits as a Potential Biosignature.

Uncovering and understanding the chemical and fossil record of ancient life is crucial to understanding how life arose, evolved, and distributed itself across Earth. Potential signs of ancient life, however, are often challenging to establish as definitively biological and require multiple lines of evidence. Hydrothermal silica deposits may preserve some of the most ancient evidence of life on Earth, and such deposits are also suggested to exist on the surface of Mars.

Phototrophic extracellular electron uptake is linked to carbon dioxide fixation in the bacterium Rhodopseudomonas palustris.

Extracellular electron uptake (EEU) is the ability of microbes to take up electrons from solid-phase conductive substances such as metal oxides. EEU is performed by prevalent phototrophic bacterial genera, but the electron transfer pathways and the physiological electron sinks are poorly understood. Here we show that electrons enter the photosynthetic electron transport chain during EEU in the phototrophic bacterium Rhodopseudomonas palustris TIE-1.

Sulfur isotope analysis of microcrystalline iron sulfides using secondary ion mass spectrometry imaging: Extracting local paleo-environmental information from modern and ancient sediments.

Rationale: Sulfur isotope ratio measurements of bulk sulfide from marine sediments have often been used to reconstruct environmental conditions associated with their formation. In situ microscale spot analyses by secondary ion mass spectrometry (SIMS) and laser ablation multiple-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) have been utilized for the same purpose. However, these techniques are often not suitable for studying small (≤10 μm) grains or for detecting intra-grain variability.

Organic carbon burial during OAE2 driven by changes in the locus of organic matter sulfurization.

Ocean Anoxic Event 2 (OAE2) was a period of dramatic disruption to the global carbon cycle when massive amounts of organic matter (OM) were buried in marine sediments via complex and controversial mechanisms. Here we investigate the role of OM sulfurization, which makes OM less available for microbial respiration, in driving variable OM preservation in OAE2 sedimentary strata from Pont d'Issole (France). We find correlations between the concentration, S:C ratio, S-isotope composition, and sulfur speciation of OM suggesting that sulfurization facilitated changes in carbon burial at this site as the chemocline moved in and out of the sediments during deposition.

Widespread nitrogen fixation in sediments from diverse deep-sea sites of elevated carbon loading.

Nitrogen fixation, the biological conversion of N to NH , is critical to alleviating nitrogen limitation in many marine ecosystems. To date, few measurements exist of N fixation in deep-sea sediments. Here, we conducted > 400 bottle incubations with sediments from methane seeps, whale falls and background sites off the western coast of the United States from 600 to 2893 m water depth to investigate the potential rates, spatial distribution and biological mediators of benthic N fixation.

Construct Validity of the Societal Outreach Scale (SOS).

Background: The American Physical Therapy Association (APTA) has been working toward a vision of increasing professional focus on societal-level health. However, performance of social responsibility and related behaviors by physical therapists remain relatively poorly integrated into practice. Promoting a focus on societal outreach is necessary for all health care professionals to impact the health of their communities.

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 (δ 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 δ S patterns and bulk δ S values. We report μm-scale δ S patterns in Proterozoic samples with well-preserved microbial mat textures.

Variability in the Raman Spectrum of Unpolished Growth and Fracture Surfaces of Pyrite Due to Laser Heating and Crystal Orientation.

Two probable causes of variability in the Raman spectrum of unpolished pyrite are well recognized, in principle, but not always in practice, namely: (1) downshifting of band positions due to laser heating; and (2) variations in the ratios of band intensities due to crystallographic orientation of the sample with respect to the laser's dominant polarization plane. The aims of this paper are to determine whether these variations can be used to acquire additional information about pyrites. Here, using laser Raman microprobe analysis of natural, unpolished pyrite samples, we investigate the magnitude of downshifting of band positions associated with laser heating of different sizes of pyrite grains.

Effect of Abrupt Discontinuation of Antidepressants in Critically Ill Hospitalized Adults.

Objectives: To determine whether discontinuation of chronic antidepressant therapy is associated with a higher risk of antidepressant discontinuation syndrome (ADS) symptoms in patients admitted to the intensive care unit (ICU) when compared with those who were continued on therapy and to identify factors associated with increased risk of ADS in this population.

Design: Single-center retrospective observational cohort study.

Setting: ICUs in a tertiary care hospital.