Interannual variation in seasonal drivers of soil respiration in a semi-arid Rocky Mountain meadow

pre-printSemi-arid ecosystems with annual moisture inputs dominated by snowmelt cover much of the western United States, and a better understanding of their seasonal drivers of soil respiration is needed to predict consequences of climatic change on soil CO2 efflux. We assessed the relative importance of temperature, moisture, and plant phenology on soil respiration during seasonal shifts between cold, wet winters and hot, dry summers in a Rocky Mountain meadow over 3.5 separate growing seasons. We found a consistent, unique pattern of seasonal hysteresis in the annual relationship between soil respiration and temperature, likely representative for this ecosystem type, and driven by (1) continued increase in soil T after summer senescence of vegetation, and (2) reduced soil respiration during cold, wet periods at the beginning versus end of the growing season. The timing of meadow senescence varied between years with amount of cold season precipitation, but on average occurred days before soil temperature peaked in late-summer. Autumn soil respiration was greatest when substantial autumn precipitation events occurred early. Surface CO2 efflux was temporarily decoupled from respiratory production during winter 2006/2007, due to effects of winter surface snow and ice on mediating the diffusion of CO2 from deep soil horizons to the atmosphere. Upon melt of a capping surface ice layer, release of soil-stored CO2 was determined to be 65 g C, or *10 % of the total growing season soil respiration for that year. The shift between soil respiration sources arising from moisture-limited spring plant growth and autumn decomposition indicates that annual mineralization of soil carbon will be less dependent on projected changes in temperature than on future variations in amount and timing of precipitation for this site and similar semiarid ecosystems

Big Data Opportunities for Global Infectious Disease Surveillance

Simon Hay and colleagues discuss the potential and challenges of producing continually updated infectious disease risk maps using diverse and large volume data sources such as social media

Stress Preconditioning of Spreading Depression in the Locust CNS

Cortical spreading depression (CSD) is closely associated with important pathologies including stroke, seizures and migraine. The mechanisms underlying SD in its various forms are still incompletely understood. Here we describe SD-like events in an invertebrate model, the ventilatory central pattern generator (CPG) of locusts. Using K+ -sensitive microelectrodes, we measured extracellular K+ concentration ([K+]o) in the metathoracic neuropile of the CPG while monitoring CPG output electromyographically from muscle 161 in the second abdominal segment to investigate the role K+ in failure of neural circuit operation induced by various stressors. Failure of ventilation in response to different stressors (hyperthermia, anoxia, ATP depletion, Na+/K+ ATPase impairment, K+ injection) was associated with a disturbance of CNS ion homeostasis that shares the characteristics of CSD and SD-like events in vertebrates. Hyperthermic failure was preconditioned by prior heat shock (3 h, 45°C) and induced-thermotolerance was associated with an increase in the rate of clearance of extracellular K+ that was not linked to changes in ATP levels or total Na+/K+ ATPase activity. Our findings suggest that SD-like events in locusts are adaptive to terminate neural network operation and conserve energy during stress and that they can be preconditioned by experience. We propose that they share mechanisms with CSD in mammals suggesting a common evolutionary origin

Cellular responses of Candida albicans to phagocytosis and the extracellular activities of neutrophils are critical to counteract carbohydrate starvation, oxidative and nitrosative stress

Acknowledgments We thank Alexander Johnson (yhb1D/D), Karl Kuchler (sodD/D mutants), Janet Quinn (hog1D/D, hog1/cap1D/D, trx1D/D) and Peter Staib (ssu1D/D) for providing mutant strains. We acknowledge helpful discussions with our colleagues from the Microbial Pathogenicity Mechanisms Department, Fungal Septomics and the Microbial Biochemistry and Physiology Research Group at the Hans Kno¨ll Institute (HKI), specially Ilse D. Jacobsen, Duncan Wilson, Sascha Brunke, Lydia Kasper, Franziska Gerwien, Sea´na Duggan, Katrin Haupt, Kerstin Hu¨nniger, and Matthias Brock, as well as from our partners in the FINSysB Network. Author Contributions Conceived and designed the experiments: PM HW IMB AJPB OK BH. Performed the experiments: PM CD HW. Analyzed the data: PM HW IMB AJPB OK BH. Wrote the paper: PM HW OK AJPB BH.Peer reviewedPublisher PD

Measuring and modelling the isotopic composition of soil respiration: insights from a grassland tracer experiment

The carbon isotopic composition (δ<sup>13</sup>C) of CO<sub>2</sub> efflux (δ<sup>13</sup>C<sub>efflux</sub>) from soil is generally interpreted to represent the actual isotopic composition of the respiratory source (δ<sup>13</sup>C<sub>Rs</sub>). However, soils contain a large CO<sub>2</sub> pool in air-filled pores. This pool receives CO<sub>2</sub> from belowground respiration and exchanges CO<sub>2</sub> with the atmosphere (via diffusion and advection) and the soil liquid phase (via dissolution). Natural or artificial modification of δ<sup>13</sup>C of atmospheric CO<sub>2</sub> (δ<sup>13</sup>C<sub>atm</sub>) or δ<sup>13</sup>C<sub>Rs</sub> causes isotopic disequilibria in the soil-atmosphere system. Such disequilibria generate divergence of δ<sup>13</sup>C<sub>efflux</sub> from δ<sup>13</sup>C<sub>Rs</sub> (termed "disequilibrium effect"). <br><br> Here, we use a soil CO<sub>2</sub> transport model and data from a <sup>13</sup>CO<sub>2</sub>/<sup>12</sup>CO<sub>2</sub> tracer experiment to quantify the disequilibrium between δ<sup>13</sup>C<sub>efflux</sub> and δ<sup>13</sup>C<sub>Rs</sub> in ecosystem respiration. The model accounted for diffusion of CO<sub>2</sub> in soil air, advection of soil air, dissolution of CO<sub>2</sub> in soil water, and belowground and aboveground respiration of both <sup>12</sup>CO<sub>2</sub> and <sup>13</sup>CO<sub>2</sub> isotopologues. The tracer data were obtained in a grassland ecosystem exposed to a δ<sup>13</sup>C<sub>atm</sub> of −46.9 ‰ during daytime for 2 weeks. Nighttime δ<sup>13</sup>C<sub>efflux</sub> from the ecosystem was estimated with three independent methods: a laboratory-based cuvette system, in-situ steady-state open chambers, and in-situ closed chambers. <br><br> Earlier work has shown that the δ<sup>13</sup>C<sub>efflux</sub> measurements of the laboratory-based and steady-state systems were consistent, and likely reflected δ<sup>13</sup>C<sub>Rs</sub>. Conversely, the δ<sup>13</sup>C<sub>efflux</sub> measured using the closed chamber technique differed from these by −11.2 ‰. Most of this disequilibrium effect (9.5 ‰) was predicted by the CO<sub>2</sub> transport model. Isotopic disequilibria in the soil-chamber system were introduced by changing δ<sup>13</sup>C<sub>atm</sub> in the chamber headspace at the onset of the measurements. When dissolution was excluded, the simulated disequilibrium effect was only 3.6 ‰. Dissolution delayed the isotopic equilibration between soil CO<sub>2</sub> and the atmosphere, as the storage capacity for labelled CO<sub>2</sub> in water-filled soil pores was 18 times that of soil air. <br><br> These mechanisms are potentially relevant for many studies of δ<sup>13</sup>C<sub>Rs</sub> in soils and ecosystems, including FACE experiments and chamber studies in natural conditions. Isotopic disequilibria in the soil-atmosphere system may result from temporal variation in δ<sup>13</sup>C<sub>Rs</sub> or diurnal changes in the mole fraction and δ<sup>13</sup>C of atmospheric CO<sub>2</sub>. Dissolution effects are most important under alkaline conditions

Surveillance of Transmitted HIV-1 Drug Resistance in Gauteng and KwaZulu-Natal Provinces, South Africa, 2005-2009

Surveillance of human immunodeficiency virus type 1 transmitted drug resistance (TDR) was conducted among pregnant women in South Africa over a 5-year period after the initiation of a large national antiretroviral treatment program. Analysis of TDR data from 9 surveys conducted between 2005 and 2009 in 2 provinces of South Africa suggests that while TDR remains low (<5%) in Gauteng Province, it may be increasing in KwaZulu-Natal, with the most recent survey showing moderate (5%-15%) levels of resistance to the nonnucleoside reverse transcriptase inhibitor drug clas

Integrative functional analysis uncovers metabolic differences between Candida species

Candida species are a dominant constituent of the human mycobiome and associated with the development of several diseases. Understanding the Candida species metabolism could provide key insights into their ability to cause pathogenesis. Here, we have developed the BioFung\ua0database, providing an efficient annotation of protein-encoding genes. Along, with BioFung, using carbohydrate-active enzyme (CAZymes) analysis, we have uncovered core and accessory features across Candida species demonstrating plasticity, adaption to the environment and acquired features. We show a greater importance of amino acid metabolism, as functional analysis revealed that all Candida species can employ amino acid metabolism. However, metabolomics revealed that only a specific cluster of species (AGAu species-C. albicans, C. glabrata and C. auris) utilised amino acid metabolism including arginine, cysteine, and methionine metabolism potentially improving their competitive fitness in pathogenesis. We further identified critical metabolic pathways in the AGAu cluster with biomarkers and anti-fungal target potential in the CAZyme profile, polyamine, choline and fatty acid biosynthesis pathways. This study, combining genomic analysis, and validation with gene expression and metabolomics, highlights the metabolic diversity with AGAu species that underlies their remarkable ability to dominate they mycobiome and cause disease

Modeling the impact of COVID-19 nonpharmaceutical interventions on respiratory syncytial virus transmission in South Africa

Background: The South African government employed various nonpharmaceutical interventions (NPIs) to reduce the spread of SARS-CoV-2. Surveillance data from South Africa indicates reduced circulation of respiratory syncytial virus (RSV) throughout the 2020–2021 seasons. Here, we use a mechanistic transmission model to project the rebound of RSV in the two subsequent seasons. Methods: We fit an age-structured epidemiological model to hospitalization data from national RSV surveillance in South Africa, allowing for time-varying reduction in RSV transmission during periods of COVID-19 circulation. We apply the model to project the rebound of RSV in the 2022 and 2023 seasons. Results: We projected an early and intense outbreak of RSV in April 2022, with an age shift to older infants (6–23 months old) experiencing a larger portion of severe disease burden than typical. In March 2022, government alerts were issued to prepare the hospital system for this potentially intense outbreak. We then assess the 2022 predictions and project the 2023 season. Model predictions for 2023 indicate that RSV activity has not fully returned to normal, with a projected early and moderately intense wave. We estimate that NPIs reduced RSV transmission between 15% and 50% during periods of COVID-19 circulation. Conclusions: A wide range of NPIs impacted the dynamics of the RSV outbreaks throughout 2020–2023 in regard to timing, magnitude, and age structure, with important implications in a low- and middle-income countries (LMICs) setting where RSV interventions remain limited. More efforts should focus on adapting RSV models to LMIC data to project the impact of upcoming medical interventions for this disease.</p