Optimal Foraging By Bacteriophages Through Host Avoidance

Optimal foraging theory explains diet restriction as an adaptation to best utilize an array of foods differing in quality, the poorest items not worth the lost opportunity of finding better ones. Although optimal foraging has traditionally been applied to animal behavior, the model is easily applied to viral host range, which is genetically determined. The usual perspective for bacteriophages ( bacterial viruses) is that expanding host range is always advantageous if fitness on former hosts is not compromised. However, foraging theory identifies conditions favoring avoidance of poor hosts even if larger host ranges have no intrinsic costs. Bacteriophage T7 rapidly evolved to discriminate among different Escherichia coli strains when one host strain was engineered to kill infecting phages but the other remained productive. After modifying bacteria to yield more subtle fitness effects on T7, we tested qualitative predictions of optimal foraging theory by competing broad and narrow host range phages against each other. Consistent with the foraging model, diet restriction was favored when good hosts were common or there was a large difference in host quality. Contrary to the model, the direction of selection was affected by the density of poor hosts because being able to discriminate was costly.Integrative Biolog

Influence of organic films on the evaporation and condensation of water in aerosol

Uncertainties in quantifying the kinetics of evaporation and condensation of water from atmospheric aerosol are a significant contributor to the uncertainty in predicting cloud droplet number and the indirect effect of aerosols on climate. The influence of aerosol particle surface composition, particularly the impact of surface active organic films, on the condensation and evaporation coefficients remains ambiguous. Here, we report measurements of the influence of organic films on the evaporation and condensation of water from aerosol particles. Significant reductions in the evaporation coefficient are shown to result when condensed films are formed by monolayers of long-chain alcohols [C(n)H((2n+1))OH], with the value decreasing from 2.4 × 10(−3) to 1.7 × 10(−5) as n increases from 12 to 17. Temperature-dependent measurements confirm that a condensed film of long-range order must be formed to suppress the evaporation coefficient below 0.05. The condensation of water on a droplet coated in a condensed film is shown to be fast, with strong coherence of the long-chain alcohol molecules leading to islanding as the water droplet grows, opening up broad areas of uncoated surface on which water can condense rapidly. We conclude that multicomponent composition of organic films on the surface of atmospheric aerosol particles is likely to preclude the formation of condensed films and that the kinetics of water condensation during the activation of aerosol to form cloud droplets is likely to remain rapid

Phosphorus behavior in sediments during a sub-seabed CO\u3csub\u3e2\u3c/sub\u3e controlled release experiment

© 2015 Elsevier Ltd. The CO2 controlled release experiment Quantifying and Monitoring Potential Ecosystem Impacts of Geological Carbon Storage (QICS) assessed the impacts of potential CO2 leakage from sub-seabed carbon capture and storage reservoirs to the marine environment. During QICS, CO2 gas was released into shallow sediment in Ardmucknish Bay, Scotland, in the spring and summer of 2012. As part of this project, we investigated the effects of CO2 leakage on sedimentary phosphorus (P), an essential nutrient for marine productivity. We found no statistically significant effects during QICS, as the solid-phase P content in the sediment was constant before, during, and after exposure to CO2. However, laboratory experiments using marine sediment standard materials as well as QICS sediment revealed substantial differences among these different sediment types in their potential for P release during CO2 exposure. Employing the SEDEX sequential extraction technique to determine the sizes of the major P pools in the sediments, we showed that calcium-bound P can be easily released by CO2 exposure, whereas iron-bound P is a major sink of released P. The overall impacts of CO2 leakage on sediment P behavior appear to be low compared to natural variability

Marine baseline and monitoring strategies for Carbon Dioxide Capture and Storage (CCS)

The QICS controlled release experiment demonstrates that leaks of carbon dioxide (CO2) gas can be detected by monitoring acoustic, geochemical and biological parameters within a given marine system. However the natural complexity and variability of marine system responses to (artificial) leakage strongly suggests that there are no absolute indicators of leakage or impact that can unequivocally and universally be used for all potential future storage sites. We suggest a multivariate, hierarchical approach to monitoring, escalating from anomaly detection to attribution, quantification and then impact assessment, as required. Given the spatial heterogeneity of many marine ecosystems it is essential that environmental monitoring programmes are supported by a temporally (tidal, seasonal and annual) and spatially resolved baseline of data from which changes can be accurately identified. In this paper we outline and discuss the options for monitoring methodologies and identify the components of an appropriate baseline survey

Weight loss surgery for non-morbidly obese populations with type 2 diabetes: is this an acceptable option for patients?

Aim To explore the views of non-morbidly obese people (BMI 30-40 kg/m2) with type 2 diabetes regarding: (a) the acceptability of bariatric surgery (BS) as a treatment for type 2 diabetes, and (b) willingness to participate in randomised controlled trials comparing BS versus non-surgical intervention. BACKGROUND: Despite weight management being a key therapeutic goal in type 2 diabetes, achieving and sustaining weight loss is problematic. BS is an effective treatment for people with morbid obesity and type 2 diabetes; it is less certain whether non-morbidly obese patients (BMI 30-39.9 kg/m2) with type 2 diabetes benefit from this treatment and whether this approach would be cost-effective. Before evaluating this issue by randomised trials, it is important to understand whether BS and such research are acceptable to this population. METHODS: Non-morbidly obese people with type 2 diabetes were purposively sampled from primary care and invited to participate in semi-structured interviews. Interviews explored participants' thoughts surrounding their diabetes and weight, the acceptability of BS and the willingness to participate in BS research. Data were analysed using Framework Analysi

The response of Li and Mg isotopes to rain events in a highly-weathered catchment

Storms are responsible for up to ~50% of total annual rainfall on tropical islands and result in rapid increases in discharge from rivers. Storm events are, however, notoriously under-sampled and their effects on weathering rates and processes are poorly constrained. To address this, we have undertaken high-frequency sampling of Quiock Creek catchment, a Critical Zone Observatory located in Guadeloupe, over a period of 21 days, encompassing several storm events. Chemical and isotopic (Li and Mg) analyses of different critical zone reservoirs (throughfall, soil pore water, groundwater and river water) were used to assess the interactions between rock, water and secondary minerals. The Li concentrations and δ7Li values of these different reservoirs range from 14 to 95 nmol/kg and 1.8 to 16.8‰, respectively. After several rain events, the average δ7Li value (13.3‰) of soil solutions from the lower part of the soil profile (>~150 cm below the surface) was unchanged, whereas in the upper part of the profile δ7Li values increased by ~2–4‰ due to increased contribution from throughfall. By contrast, the δ26Mg value of soil waters in the upper part of the soil profile were not significantly affected by the rain events with an average value of −0.90‰. The δ26Mg values of the different fluid reservoirs were generally close to the value of throughfall (~−0.90‰), but higher δ26Mg values (up to −0.58‰) were measured in the deeper parts of the soil profile, whereas groundwaters that have a long residence time had lower δ26Mg values (down to −1.48‰). These higher and lower values are attributed to, respectively, adsorption/desorption of light Mg isotopes on/from the surface of clay minerals. The δ7Li value of the river waters was ~9.3‰, with a Li concentration of 60 μmol/kg, but during a storm these values decreased to, respectively, 7.8‰ and 40 μmol/kg. This change in δ7Li is consistent with an increased contribution of Li from the soil solution. Thus, even in highly weathered catchments, changes in hydrological conditions can have a significant impact on weathering processes and therefore the composition of river waters delivered to the ocean

Behaviour of chromium isotopes in the eastern sub-tropical Atlantic Oxygen Minimum Zone

Constraints on the variability of chromium (Cr) isotopic compositions in the modern ocean are required to validate the use of Cr isotopic signatures in ancient authigenic marine sediments for reconstructing past levels of atmospheric and ocean oxygenation. This study presents dissolved Cr concentrations (CrT, where CrT = Cr(VI) + Cr(III)) and Cr isotope data (δ53Cr) for shelf, slope and open ocean waters within the oxygen minimum zone (OMZ) of the eastern sub-tropical Atlantic Ocean. Although dissolved oxygen concentrations were as low as 44–90 μmol kg−1 in the core of the OMZ, there was no evidence for removal of Cr(VI). Nonetheless, there was significant variability in seawater δ53Cr, with values ranging from 1.08 to 1.72‰. Shelf CrT concentrations were slightly lower (2.21 ± 0.07 nmol kg−1) than in open ocean waters at the same water depth (between 0 and 160 m, 2.48 ± 0.07 nmol kg−1). The shelf waters also had higher δ53Cr values (1.41 ± 0.14‰ compared to 1.18 ± 0.05‰ for open ocean waters shallower than 160 m). This is consistent with partial reduction of Cr(VI) to Cr(III), with subsequent removal of isotopically light Cr(III) onto biogenic particles. We also provide evidence for input of relatively isotopically heavy Cr from sediments on the shelf. Intermediate and deep water masses (AAIW and NADW) show a rather limited range of δ53Cr values (1.19 ± 0.09‰) and inputs of Cr from remineralisation of organic material or re-oxidation of Cr(III) appear to be minimal. Authigenic marine precipitates deposited in deep water in the open ocean therefore have the potential to faithfully record seawater δ53Cr, whereas archives of seawater δ53Cr derived from shelf sediments must be interpreted with caution

Phosphorus behavior in sediments during a sub-seabed CO2 controlled release experiment

The CO2 controlled release experiment “Quantifying and Monitoring Potential Ecosystem Impacts of Geological Carbon Storage” (QICS) assessed the impacts of potential CO2 leakage from sub-seabed carbon capture and storage reservoirs to the marine environment. During QICS, CO2 gas was released into shallow sediment in Ardmucknish Bay, Scotland, in the spring and summer of 2012. As part of this project, we investigated the effects of CO2 leakage on sedimentary phosphorus (P), an essential nutrient for marine productivity. We found no statistically significant effects during QICS, as the solid-phase P content in the sediment was constant before, during, and after exposure to CO2. However, laboratory experiments using marine sediment standard materials as well as QICS sediment revealed substantial differences among these different sediment types in their potential for P release during CO2 exposure. Employing the SEDEX sequential extraction technique to determine the sizes of the major P pools in the sediments, we showed that calcium-bound P can be easily released by CO2 exposure, whereas iron-bound P is a major sink of released P. The overall impacts of CO2 leakage on sediment P behavior appear to be low compared to natural variability

Carbon dioxide generation and drawdown during active orogenesis of siliciclastic rocks in the Southern Alps, New Zealand

C.D.M. was supported by NERC CASE PhD studentship award NE/G524160/1 (GNS Science, NZ, CASE partner). D.A.H.T. acknowledges support from research grants NE/H012842/1 and NE/J022128/1 and a Royal Society Wolfson Research Merit Award (WM130051). S.C.C. was funded under GNS Science's “Impacts of Global Plate Tectonics in and around New Zealand Programme” (PGST Contract CO5X0203). J.C.A. was supported by NSF OCE1334758. We also thank Matthew Cooper, Andy Milton, Darryl Green and Lora Wingate for laboratory assistance. We thank Mike Bickle for editorial advice and comments, and reviews from two anonymous reviewers that improved this manuscript.Peer reviewedPublisher PD