Above‐ and belowground linkages in Sphagnum peatland: climate warming affects plant‐microbial interactions

Peatlands contain approximately one third of all soil organic carbon (SOC). Warming can alter above‐ and belowground linkages that regulate soil organic carbon dynamics and C‐balance in peatlands. Here we examine the multiyear impact of in situ experimental warming on the microbial food web, vegetation, and their feedbacks with soil chemistry. We provide evidence of both positive and negative impacts of warming on specific microbial functional groups, leading to destabilization of the microbial food web. We observed a strong reduction (70%) in the biomass of top‐predators (testate amoebae) in warmed plots. Such a loss caused a shortening of microbial food chains, which in turn stimulated microbial activity, leading to slight increases in levels of nutrients and labile C in water. We further show that warming altered the regulatory role of Sphagnum‐polyphenols on microbial community structure with a potential inhibition of top predators. In addition, warming caused a decrease in Sphagnum cover and an increase in vascular plant cover. Using structural equation modelling, we show that changes in the microbial food web affected the relationships between plants, soil water chemistry, and microbial communities. These results suggest that warming will destabilize C and nutrient recycling of peatlands via changes in above‐ and belowground linkages, and therefore, the microbial food web associated with mosses will feedback positively to global warming by destabilizing the carbon cycle. This study confirms that microbial food webs thus constitute a key element in the functioning of peatland ecosystems. Their study can help understand how mosses, as ecosystem engineers, tightly regulate biogeochemical cycling and climate feedback in peatlands     

Resizing a River: A Downscaled,Seasonal Flow Regime Promotes Riparian Restoration

While riverine organisms are adapted to the natural flow regime, it is impractical to fully restore natural flows along most regulated rivers. We propose an alternative with the delivery of downscaled flow regimes that provide the seasonal patterns that are essential for aquatic and riparian ecosystems. The Bridge River in British Columbia provided a novel case study as a downscaled flow regime commenced in 2000 along a reach that had generally experienced no flow for the prior half‐century. The experimental flow delivered a mean discharge of about 3 m³/s, versus the pre‐dam mean of 100 m³/s, with a seasonal pattern that mimicked the natural snowmelt‐dominated pattern. To assess the environmental response, we investigated black cottonwoods, Populus trichocarpa, the dominant riparian trees, in the pre‐flow versus post‐flow intervals, using tree ring interpretation for growth analyses and age determination. Sparse mature trees established prior to the 1948 damming did not show significant growth changes in the pre‐ versus post‐flow intervals. In contrast, younger trees that established closer to the river in the decade prior to 2000 displayed significant growth increases by 2002, and juveniles established after 2000 demonstrated faster initial growth than juveniles established before 2000. Further, bands of cottonwood saplings resulted from seedling recruitment along the new river fringe, particularly in 2002, 2003, and 2004, years with gradual flow recession. These responses demonstrate that a downscaled, seasonal flow regime provided environmental benefit, thereby restoring some river function and resulting in a resized river flanked by narrow and reproducing cottonwood bands.     

The anti-sigma factor TcdC modulates hypervirulence in an epidemic BI/NAP1/027 clinical isolate of Clostridium difficile

Nosocomial infections are increasingly being recognised as a major patient safety issue. The modern hospital environment and associated health care practices have provided a niche for the rapid evolution of microbial pathogens that are well adapted to surviving and proliferating in this setting, after which they can infect susceptible patients. This is clearly the case for bacterial pathogens such as Methicillin Resistant Staphylococcus aureus (MRSA) and Vancomycin Resistant Enterococcus (VRE) species, both of which have acquired resistance to antimicrobial agents as well as enhanced survival and virulence properties that present serious therapeutic dilemmas for treating physicians. It has recently become apparent that the spore-forming bacterium Clostridium difficile also falls within this category. Since 2000, there has been a striking increase in C. difficile nosocomial infections worldwide, predominantly due to the emergence of epidemic or hypervirulent isolates that appear to possess extended antibiotic resistance and virulence properties. Various hypotheses have been proposed for the emergence of these strains, and for their persistence and increased virulence, but supportive experimental data are lacking. Here we describe a genetic approach using isogenic strains to identify a factor linked to the development of hypervirulence in C. difficile. This study provides evidence that a naturally occurring mutation in a negative regulator of toxin production, the anti-sigma factor TcdC, is an important factor in the development of hypervirulence in epidemic C. difficile isolates, presumably because the mutation leads to significantly increased toxin production, a contentious hypothesis until now. These results have important implications for C. difficile pathogenesis and virulence since they suggest that strains carrying a similar mutation have the inherent potential to develop a hypervirulent phenotype.     

Trivalent adenovirus type 5 HIV recombinant vaccine primes for modest cytotoxic capacity that is greatest in humans with protective HLA class I alleles

If future HIV vaccine design strategies are to succeed, improved understanding of the mechanisms underlying protection from infection or immune control over HIV replication remains essential. Increased cytotoxic capacity of HIV-specific CD8+ T-cells associated with efficient elimination of HIV-infected CD4+ T-cell targets has been shown to distinguish long-term nonprogressors (LTNP), patients with durable control over HIV replication, from those experiencing progressive disease. Here, measurements of granzyme B target cell activity and HIV-1-infected CD4+ T-cell elimination were applied for the first time to identify antiviral activities in recipients of a replication incompetent adenovirus serotype 5 (Ad5) HIV-1 recombinant vaccine and were compared with HIV-negative individuals and chronically infected patients, including a group of LTNP. We observed readily detectable HIV-specific CD8+ T-cell recall cytotoxic responses in vaccinees at a median of 331 days following the last immunization. The magnitude of these responses was not related to the number of vaccinations, nor did it correlate with the percentages of cytokine-secreting T-cells determined by ICS assays. Although the recall cytotoxic capacity of the CD8+ T-cells of the vaccinee group was significantly less than that of LTNP and overlapped with that of progressors, we observed significantly higher cytotoxic responses in vaccine recipients carrying the HLA class I alleles B*27, B*57 or B*58, which have been associated with immune control over HIV replication in chronic infection. These findings suggest protective HLA class I alleles might lead to better outcomes in both chronic infection and following immunization due to more efficient priming of HIV-specific CD8+ T-cell cytotoxic responses.     

Palaeoenvironment and taphonomy of a Late Jurassic (Late Tithonian) Lagerstätte from central Poland

A rich assemblage of exceptionally preserved marine and terrestrial fossils occurs in fine‐grained limestones in the upper part of the Late Tithonian (Middle Volgian) shallowing upward carbonate sequence in Central Poland. The richest horizon, a deposit known locally as the Corbulomima horizon, is named after the shallow burrowing suspension feeding bivalve Corbulomima obscura, moulds of which occur in densities of up to 500 per square metre on some bedding planes. The fauna in this bed also includes organic and phosphatic remains of a wide range of other creatures including the exuviae of limulids and decapods, disarticulated fish skeletons and rare isolated pterosaur bones and teeth. There are also perfectly preserved dragonfly wings and beetle exoskeletons. The average stable carbon and oxygen isotope values for ostracod shells and fine‐grained sediment from this horizon suggest precipitation of the calcium carbonate from warm seawater of normal marine salinity. The carbonate sediments overlying the fossiliferous horizon have been interpreted as nearshore to shoreface facies. These pass abruptly into coarse reworked intraclastic sediments interpreted as possible tsunami or storm surge over‐wash deposits. The clasts in this deposit have more positive oxygen isotope values than those in the underlying limestone, which may indicate that they were lithified in a slightly more evaporative, perhaps intertidal, setting. The succession terminates with silicified fine‐grained limestones likely to have formed in extremely shallow lagoonal environments. In contrast with the Solnhofen limestones of Lower Tithonian age in south‐central Germany the Corbulomima horizon is interpreted as a transitional deposit formed in a shallow marine setting by rapid burial with elements of both Konservat‐ and Konzentrat‐Lagerstätte preservation. □Konzentrat and Konservat‐Lagerstätte, Taphonomy, Palaeoenvironment, Paleogeography, Late Jurassic, Poland.     

Independent and combined effects of eating rate and energy density on energy intake,appetite, and gut hormones

Objective:

Energy density (ED) and eating rate (ER) influence energy intake; their combined effects on intake and on postprandial pancreatic and gut hormone responses are undetermined. To determine the combined effects of ED and ER manipulation on voluntary food intake, subjective appetite, and postprandial pancreatic and gut hormone responses.

Design and Methods:

Twenty nonobese volunteers each consumed high (1.6 kcal g^?1; HED) and low (1.2 kcal g^?1; LED) ED breakfasts slowly (20 g min^?1; SR) and quickly (80 g min^?1; FR) ad libitum to satiation. Appetite, and pancreatic and gut hormone concentrations were measured periodically over 3 h. Ad libitum energy intake during the subsequent lunch was then measured.

Results:

Main effects of ED and ER on energy intake and a main effect of ER, but not ED, on mass of food consumed were observed, FR and HED being associated with increased intake (P < 0.05). Across all conditions, energy intake was highest during FR‐HED (P ≤ 0.01). Area under the curve (AUC) of appetite ratings was not different between meals. Main effects of ED and ER on insulin, peptide‐YY, and glucagon‐like peptide‐1 AUC (P < 0.05) were observed, FR and HED being associated with larger AUC. No effects on active or total ghrelin AUC were documented. Total energy intake over both meals was highest during the FR‐HED trial with the greatest difference between FR‐HED and SR‐LED trials (P ≤ 0.01).

Conclusion:

Consuming an energy dense meal quickly compounds independent effects of ER and ED on energy intake. Energy compensation at the following meal may not occur despite altered gut hormone responses.

     

Consistent growth of black cottonwoods despite temperature variation across elevational ecoregions in the Rocky Mountains

Globally, water and temperature provide the dominant environmental determinants of tree distribution and growth. In riparian or streamside zones, groundwater is abundant, and we consequently predicted that temperature would limit the growth of riparian cottonwoods in a cool climate northern mountain region. To investigate this association, we analyzed tree rings of 167 black cottonwoods, Populus trichocarpa, along two adjacent Rocky Mountain creeks in Alberta. Cottonwoods were sampled from 1700 m, near their upper elevational limit, down 500 m through three progressively warmer ecoregions, the montane, aspen parkland, and fescue prairie. Across these zones, June through September mean temperatures rose from 12.4 to 16.2°C (lapse rate = 0.67°C/100 m), and there was subsequently a 42% increase in growing degree days (base 5°C, GDD₅) from 900 GDD₅ at the trees’ upper limit. Despite this variation, growth rate of most trees was fairly consistent across the ecoregions; trunk diameter versus age associations were relatively similar (r ² = 0.85) with an estimated 14% increase in trunk sizes of 50 year-old trees with decreasing elevation. In all ecoregions, developmental patterns were prominent as annual radial increments increased up to about 20 years, and then progressively declined to an apparent lethal threshold of about 0.4 mm/year at about 100 years. Basal area increments also increased through the juvenile phase, but remained fairly constant thereafter. The weak association between growth and temperature suggests that other environmental factors limited growth rates or there were differences in temperature adaptation across these elevational ecoregions. The results suggest that predicted regional climate warming may not substantially promote the growth rates of these Rocky Mountain trees.     

Distinct Innate Immune Phagocyte Responses to Aspergillus fumigatus Conidia and Hyphae in Zebrafish Larvae

Aspergillus fumigatus is the most common filamentous fungal pathogen of immunocompromised hosts, resulting in invasive aspergillosis (IA) and high mortality rates. Innate immunity is known to be the predominant host defense against A. fumigatus; however, innate phagocyte responses to A. fumigatus in an intact host and their contributions to host survival remain unclear. Here, we describe a larval zebrafish A. fumigatus infection model amenable to real-time imaging of host-fungal interactions in live animals. Following infection with A. fumigatus, innate phagocyte populations exhibit clear preferences for different fungal morphologies: macrophages rapidly phagocytose conidia and form aggregates around hyphae, while the neutrophil response is dependent upon the presence of hyphae. Depletion of macrophages rendered host larvae susceptible to invasive disease. Moreover, a zebrafish model of human leukocyte adhesion deficiency with impaired neutrophil function also resulted in invasive disease and impaired host survival. In contrast, macrophage-deficient but not neutrophil-deficient larvae exhibited attenuated disease following challenge with a less virulent (ΔlaeA) strain of A. fumigatus, which has defects in secondary metabolite production. Taking these results together, we have established a new vertebrate model for studying innate immune responses to A. fumigatus that reveals distinct roles for neutrophils and macrophages in mediating host defense against IA.     

Effective group training for patients with unexplained physical symptoms: a randomized controlled trial with a non-randomized one-year follow-up

Background

Although cognitive-behavioral therapy for Unexplained Physical Symptoms (UPS) is effective in secondary care, studies done in primary care produced implementation problems and conflicting results. We evaluated the effectiveness of a cognitive-behavioral group training tailored to primary care patients and provided by a secondary community mental-health service reaching out into primary care.

Methodology/Principal Findings

The effectiveness of this training was explored in a randomized controlled trial. In this trial, 162 patients with UPS classified as undifferentiated somatoform disorder or as chronic pain disorder were randomized either to the training or a waiting list. Both lasted 13 weeks. The preservation of the training''s effect was analyzed in non-randomized follow-ups, for which the waiting group started the training after the waiting period. All patients attended the training were followed-up after three months and again after one year. The primary outcomes were the physical and the mental summary scales of the SF-36. Secondary outcomes were the other SF-36-scales and the SCL-90-R. The courses of the training''s effects in the randomized controlled trial and the follow-ups were analyzed with linear mixed modeling. In the randomized controlled trial, the training had a significantly positive effect on the quality of life in the physical domain (Cohen''s d = 0.38;p = .002), but this overall effect was not found in the mental domain. Regarding the secondary outcomes, the training resulted in reporting an improved physical (Cohen''s d = 0.43;p = 0.01), emotional (Cohen''s d = 0.44;p = .0.01), and social (Cohen''s d = 0.36;p = 0.01) functioning, less pain and better functioning despite pain (Cohen''s d = 0.51;p = <0.001), less physical symptoms (Cohen''s d = −.23;p = 0.05) and less sleep difficulties (Cohen''s d = −0.25;p = 0.04) than time in the waiting group. During the non-randomized follow-ups, there were no relapses.

Conclusions/Significance

The cognitive-behavioral group training tailored for UPS in primary care and provided by an outreaching secondary mental-health service appears to be effective and to broaden the accessibility of treatment for UPS.

Trial Registration

TrialRegister.nl NTR1609 <rctview.asp?TC = 1609>     

Transgenic modification of gai or rgl1 causes dwarfing and alters gibberellins, root growth, and metabolite profiles in Populus

In Arabidopsis and other plants, gibberellin (GA)-regulated responses are mediated by proteins including GAI, RGA and RGL1-3 that contain a functional DELLA domain. Through transgenic modification, we found that DELLA-less versions of GAI (gai) and RGL1 (rgl1) in a Populus tree have profound, dominant effects on phenotype, producing pleiotropic changes in morphology and metabolic profiles. Shoots were dwarfed, likely via constitutive repression of GA-induced elongation, whereas root growth was promoted two- to threefold in vitro. Applied GA₃ inhibited adventitious root production in wild-type poplar, but gai/rgl1 poplars were unaffected by the inhibition. The concentrations of bioactive GA₁ and GA₄ in leaves of gai- and rgl1-expressing plants increased 12- to 64-fold, while the C₁₉ precursors of GA₁ (GA₅₃, GA₄₄ and GA₁₉) decreased three- to ninefold, consistent with feedback regulation of GA 20-oxidase in the transgenic plants. The transgenic modifications elicited significant metabolic changes. In roots, metabolic profiling suggested increased respiration as a possible mechanism of the increased root growth. In leaves, we found metabolite changes suggesting reduced carbon flux through the lignin biosynthetic pathway and a shift towards allocation of secondary storage and defense metabolites, including various phenols, phenolic glucosides, and phenolic acid conjugates.