Strontium isotopes trace biological activity in the Critical Zone along a climate and vegetation gradient

Weathering and ecosystem nutrition are intimately linked through the supply of fresh mineral nutrients from regolith and bedrock (the "geogenic nutrient pathway"). However, the prominence of this link is dependent on the efficiency of nutrient recycling from plant litter (the "organic nutrient cycle"). Isotope ratios of strontium (Sr), an element that behaves similarly to Ca in ecosystems, confer two types of information: radiogenic Sr isotopes inform as to the sources of Sr and the degree of weathering, while stable Sr isotopes constrain partitioning between compartments of the Critical Zone (bedrock, water, secondary solids, and plants). To date, however, neither the reactions nor the mass balance between compartments that fractionate Sr isotopes, nor the fractionation factors involved, are well understood. Here, we present geochemical budgets of Sr (using radio genic and stable Sr isotopes, and Ca/Sr ratios) at four sites along a substantial climate and primary production gradient in the coastal mountains of Chile. We found that Sr release through weathering is isotopically congruent, and released Sr is not strongly isotopically fractionated either during secondary mineral formation or transfer into the exchangeable pool. Despite this, the Sr-88/Sr-86 ratio of bio-available Sr, which should reflect the ratio of dissolved Sr, is higher than that of rock and regolith. We propose that this offset is caused by plants: while Sr-88/Sr-86 in plant organs at the four study sites systematically increased from roots towards their leaves, whole-plant Sr isotope compositions indicate preferential uptake of light Sr into plants (with a fractionation of up to -0.3 parts per thousand relative to the bio-available pool). Despite this strong biological fractionation, Sr-88/Sr-86 ratios in bio-available Sr do not covary with biomass production across our study sites, because with greater plant growth Sr is recycled more times after release by weathering - an isotope-neutral process. Rather, the loss of Sr from the ecosystem in solid organic material sets the isotope ratio of dissolved or bio-available Sr. Organic solids thus appear to constitute a significant export path of elements released during weathering, with the removal of solid plant debris reducing the recycling factor of Sr, and possibly that of other mineral nutrients too

Do degree and rate of silicate weathering depend on plant productivity?

Plants and their associated below-ground microbiota possess the tools for rock weathering. Yet the quantitative evaluation of the impact of these biogenic weathering drivers relative to abiogenic parameters, such as the supply of primary minerals, water, and acids, is an open question in Critical Zone research. Here we present a novel strategy to decipher the relative impact of these drivers. We quantified the degree and rate of weathering and compared these to nutrient uptake along the "EarthShape" transect in the Chilean Coastal Cordillera. These sites define a major north-south gradient in precipitation and primary productivity but overlie granitoid rock throughout. We present a dataset of the chemistry of Critical Zone compartments (bedrock, regolith, soil, and vegetation) to quantify the relative loss of soluble elements (the "degree of weathering") and the inventory of bioavailable elements. We use (87)Sra center dot Sr-86 isotope ratios to identify the sources of mineral nutrients to plants. With rates from cosmogenic nuclides and biomass growth we determined fluxes ("weathering rates"), meaning the rate of loss of elements out of the ecosystems, averaged over weathering timescales (millennia), and quantified mineral nutrient recycling between the bulk weathering zone and the bulk vegetation cover. We found that neither the degree of weathering nor the weathering rates increase systematically with precipitation from north to south along the climate and vegetation gradient. Instead, the increase in biomass nutrient demand is accommodated by faster nutrient recycling. In the absence of an increase in weathering rate despite a five-fold increase in precipitation and net primary productivity (NPP), we hypothesize that plant growth might in fact dampen weathering rates. Because plants are thought to be key players in the global silicate weathering-carbon feedback, this hypothesis merits further evaluation

PCR for the detection of pathogens in neonatal early onset sepsis.

BACKGROUND: A large proportion of neonates are treated for presumed bacterial sepsis with broad spectrum antibiotics even though their blood cultures subsequently show no growth. This study aimed to investigate PCR-based methods to identify pathogens not detected by conventional culture. METHODS: Whole blood samples of 208 neonates with suspected early onset sepsis were tested using a panel of multiplexed bacterial PCRs targeting Streptococcus pneumoniae, Streptococcus agalactiae (GBS), Staphylococcus aureus, Streptococcus pyogenes (GAS), Enterobacteriaceae, Enterococcus faecalis, Enterococcus faecium, Ureaplasma parvum, Ureaplasma urealyticum, Mycoplasma hominis and Mycoplasma genitalium, a 16S rRNA gene broad-range PCR and a multiplexed PCR for Candida spp. RESULTS: Two-hundred and eight samples were processed. In five of those samples, organisms were detected by conventional culture; all of those were also identified by PCR. PCR detected bacteria in 91 (45%) of the 203 samples that did not show bacterial growth in culture. S. aureus, Enterobacteriaceae and S. pneumoniae were the most frequently detected pathogens. A higher bacterial load detected by PCR was correlated positively with the number of clinical signs at presentation. CONCLUSION: Real-time PCR has the potential to be a valuable additional tool for the diagnosis of neonatal sepsis

Mantle-derived trace element variability in olivines and their melt inclusions

Trace element variability in oceanic basalts is commonly used to constrain the physics of mantle melting and the chemistry of Earth's deep interior. However, the geochemical properties of mantle melts are often overprinted by mixing and crystallisation processes during ascent and storage. Studying primitive melt inclusions offers one solution to this problem, but the fidelity of the melt-inclusion archive to bulk magma chemistry has been repeatedly questioned. To provide a novel check of the melt inclusion record, we present new major and trace element analyses from olivine macrocrysts in the products of two geographically proximal, yet compositionally distinct, primitive eruptions from the Reykjanes Peninsula of Iceland. By combining these macrocryst analyses with new and published melt inclusion analyses we demonstrate that olivines have similar patterns of incompatible trace element (ITE) variability to the inclusions they host, capturing chemical systematics on intra- and inter-eruption scales. ITE variability (element concentrations, ratios, variances and variance ratios) in olivines from the ITE-enriched Stapafell eruption is best accounted for by olivine-dominated fractional crystallisation. In contrast, ITE variability in olivines and inclusions from the ITE-depleted Háleyjabunga eruption cannot be explained by crystallisation alone, and must have originated in the mantle. Compatible trace element (CTE) variability is best described by crystallisation processes in both eruptions. Modest correlations between host and inclusion ITE contents in samples from Háleyjabunga suggest that melt inclusions can be faithful archives of melting and magmatic processes. It also indicates that degrees of ITE enrichment can be estimated from olivines directly when melt inclusion and matrix glass records of geochemical variability are poor or absent. Inter-eruption differences in olivine ITE systematics between Stapafell and Háleyjabunga mirror differences in melt inclusion suites, and confirm that the Stapafell eruption was fed by lower degree melts from greater depths within the melting region than the Háleyjabunga eruption. Although olivine macrocrysts from Stapafell are slightly richer in Ni than those from Háleyjabunga, their overall CTE systematics (e.g., Ni/(Mg/Fe), Fe/Mn and Zn/Fe) are inconsistent with being derived from olivine-free pyroxenites. However, the major element systematics of Icelandic basalts require lithological heterogeneity in their mantle source in the form of Fe-rich and hence fusible domains. We thus conclude that enriched heterogeneities in the Icelandic mantle are composed of modally enriched, yet nonetheless olivine-bearing, lithologies and that olivine CTE contents provide an incomplete record of lithological heterogeneity in the mantle. Modally enriched peridotites may therefore play a more important role in oceanic magma genesis than previously inferred.</p

Surveillance of congenital Zika syndrome in England and Wales: methods and results of laboratory, obstetric and paediatric surveillance.

The spread of the Zika virus (ZIKV) in the Americas led to large outbreaks across the region and most of the Southern hemisphere. Of greatest concern were complications following acute infection during pregnancy. At the beginning of the outbreak, the risk to unborn babies and their clinical presentation was unclear. This report describes the methods and results of the UK surveillance response to assess the risk of ZIKV to children born to returning travellers. Established surveillance systems operating within the UK - the paediatric and obstetric surveillance units for rare diseases, and national laboratory monitoring - enabled rapid assessment of this emerging public health threat. A combined total of 11 women experiencing adverse pregnancy outcomes after possible ZIKV exposure were reported by the three surveillance systems; five miscarriages, two intrauterine deaths and four children with clinical presentations potentially associated with ZIKV infection. Sixteen women were diagnosed with ZIKV during pregnancy in the UK. Amongst the offspring of these women, there was unequivocal laboratory evidence of infection in only one child. In the UK, the number and risk of congenital ZIKV infection for travellers returning from ZIKV-affected countries is very small

The detection of airborne transmission of tuberculosis from HIV-infected patients, using an in vivo air sampling model

Background. Nosocomial transmission of tuberculosis remains an important public health problem. We created an in vivo air sampling model to study airborne transmission of tuberculosis from patients coinfected with human immunodeficiency virus (HIV) and to evaluate environmental control measures. Methods. An animal facility was built above a mechanically ventilated HIV‐tuberculosis ward in Lima, Peru. A mean of 92 guinea pigs were continuously exposed to all ward exhaust air for 16 months. Animals had tuberculin skin tests performed at monthly intervals, and those with positive reactions were removed for autopsy and culture for tuberculosis. Results. Over 505 consecutive days, there were 118 ward admissions by 97 patients with pulmonary tuberculosis, with a median duration of hospitalization of 11 days. All patients were infected with HIV and constituted a heterogeneous group with both new and existing diagnoses of tuberculosis. There was a wide variation in monthly rates of guinea pigs developing positive tuberculin test results (0%–53%). Of 292 animals exposed to ward air, 159 developed positive tuberculin skin test results, of which 129 had laboratory confirmation of tuberculosis. The HIV‐positive patients with pulmonary tuberculosis produced a mean of 8.2 infectious quanta per hour, compared with 1.25 for HIV‐negative patients with tuberculosis in similar studies from the 1950s. The mean monthly patient infectiousness varied greatly, from production of 0–44 infectious quanta per hour, as did the theoretical risk for a health care worker to acquire tuberculosis by breathing ward air. Conclusions. HIV‐positive patients with tuberculosis varied greatly in their infectiousness, and some were highly infectious. Use of environmental control strategies for nosocomial tuberculosis is therefore a priority, especially in areas with a high prevalence of both tuberculosis and HIV infection

Factors controlling rare earth element plus yttrium enrichment in Fe–Mn crusts from Canary Islands Seamounts (NE Central Atlantic)

Marine minerals are important because concentrate in their structure high contents of strategic and critical elements as rare earth elements. Forty-two samples from eight seamounts of Canary Islands Seamount Province (CISP) have been analyzed in order to evaluate their rare earth elements plus yttrium contents (REY). Highest contents of REY are related to hydrogenetic minerals and essentially Fe-vernadite (on average 3000 μg/g). Diagenetic minerals, on the other hand, show the lowest REY contents with an average content of 260 μg/g. These differences also depend on the growth rates, hydrogenetic minerals with growth rates between 0.5 and 5 mm/Ma allow the incorporation of more REY in their structure. REY contents in studied samples varies depending several factors associated with depth and location, shallowest samples presumably growth near or within the oxygen minimum zone are the most enriched with up to 3800 μg/g due to local enrichment of these elements and the slowest growth rate promoted by the reduced ambient conditions while deeper samples around 3000 m water depth show 2800 μg/g. Location also has a role in REY contents essentially due to the presence of different currents. Samples faced to north are exposed to the more oxygenated waters of the North Atlantic Deep Water and are depleted in REY if compared with deeper samples facing to south to the more oxic Antarctic Bottom Water. Finally, the case of study made on three different seamounts of the CISP show that Fe–Mn crusts from this area could provide on average 130 tons of hydrometallurgical recovered REY (based on 1 km2 areal crust coverage) together with interesting quantity of several other strategic and base elements as Mn, Co, Ni, Cu, V, Mo between others

Genome analysis of the necrotrophic fungal pathogens Sclerotinia sclerotiorum and Botrytis cinerea

Sclerotinia sclerotiorum and Botrytis cinerea are closely related necrotrophic plant pathogenic fungi notable for their wide host ranges and environmental persistence. These attributes have made these species models for understanding the complexity of necrotrophic, broad host-range pathogenicity. Despite their similarities, the two species differ in mating behaviour and the ability to produce asexual spores. We have sequenced the genomes of one strain of S. sclerotiorum and two strains of B. cinerea. The comparative analysis of these genomes relative to one another and to other sequenced fungal genomes is provided here. Their 38–39 Mb genomes include 11,860–14,270 predicted genes, which share 83% amino acid identity on average between the two species. We have mapped the S. sclerotiorum assembly to 16 chromosomes and found large-scale co-linearity with the B. cinerea genomes. Seven percent of the S. sclerotiorum genome comprises transposable elements compared t