Ca2+-stabilized adhesin helps an Antarctic bacterium reach out and bind ice

The large size of a 1.5-MDa ice-binding adhesin [MpAFP (Marinomonas primoryensis antifreeze protein)] from an Antarctic Gram-negative bacterium, M. primoryensis, is mainly due to its highly repetitive RII (Region II). MpAFP_RII contains roughly 120 tandem copies of an identical 104-residue repeat. We have previously determined that a single RII repeat folds as a Ca²⁺-dependent immunoglobulin-like domain. Here, we solved the crystal structure of RII tetra-tandemer (four tandem RII repeats) to a resolution of 1.8 Å. The RII tetra-tandemer reveals an extended (~190-Å × ~25-Å), rod-like structure with four RII-repeats aligned in series with each other. The inter-repeat regions of the RII tetra-tandemer are strengthened by Ca²⁺ bound to acidic residues. SAXS (small-angle X-ray scattering) profiles indicate the RII tetra-tandemer is significantly rigidified upon Ca²⁺ binding, and that the protein''s solution structure is in excellent agreement with its crystal structure. We hypothesize that >600 Ca²⁺ help rigidify the chain of ~120 104-residue repeats to form a ~0.6 μm rod-like structure in order to project the ice-binding domain of MpAFP away from the bacterial cell surface. The proposed extender role of RII can help the strictly aerobic, motile bacterium bind ice in the upper reaches of the Antarctic lake where oxygen and nutrients are most abundant. Ca²⁺-induced rigidity of tandem Ig-like repeats in large adhesins might be a general mechanism used by bacteria to bind to their substrates and help colonize specific niches.     

Peripheral blood T-cell signatures from high-resolution immune phenotyping of γδ and αβ T-cells in younger and older subjects in the Berlin Aging Study II

Background

Aging and latent infection with Cytomegalovirus (CMV) are thought to be major factors driving the immune system towards immunosenescence, primarily characterized by reduced amounts of naïve T-cells and increased memory T-cells, potentially associated with higher morbidity and mortality. The composition of both major compartments, γδ as well as αβ T-cells, is altered by age and CMV, but detailed knowledge of changes to the γδ subset is currently limited.

Results

Here, we have surveyed a population of 73 younger (23–35 years) and 144 older (62–85 years) individuals drawn from the Berlin Aging Study II, investigating the distribution of detailed differentiation phenotypes of both γδ and αβ T-cells. Correlation of frequencies and absolute counts of the identified phenotypes with age and the presence of CMV revealed a lower abundance of Vδ2-positive and a higher amount of Vδ1-positive cells. We found higher frequencies of late-differentiated and lower frequencies of early-differentiated cells in the Vδ1+ and Vδ1-Vδ2-, but not in the Vδ2+ populations in elderly CMV-seropositive individuals confirming the association of these Vδ2-negative cells with CMV-immunosurveillance. We identified the highest Vδ1:Vδ2 ratios in the CMV-seropositive elderly. The observed increased CD4:CD8 ratios in the elderly were significantly lower in CMV-seropositive individuals, who also possessed a lower naïve and a larger late-differentiated compartment of CD8+ αβ T-cells, reflecting the consensus in the literature.

Conclusions

Our findings illustrate in detail the strong influence of CMV on the abundance and differentiation pattern of γδ T-cells as well as αβ T-cells in older and younger people. Mechanisms responsible for the phenotypic alterations in the γδ T-cell compartment, associated both with the presence of CMV and with age require further clarification.

     

Skeletal Muscle Depletion and Markers for Cancer Cachexia Are Strong Prognostic Factors in Epithelial Ovarian Cancer

ObjectiveTumor cachexia is an important prognostic parameter in epithelial ovarian cancer (EOC). Tumor cachexia is characterized by metabolic and inflammatory disturbances. These conditions might be reflected by body composition measurements (BCMs) ascertained by pre-operative computed tomography (CT). Thus, we aimed to identify the prognostically most relevant BCMs assessed by pre-operative CT in EOC patients.MethodsWe evaluated muscle BCMs and well established markers of nutritional and inflammatory status, as well as clinical-pathological parameters in 140 consecutive patients with EOC. Furthermore, a multiplexed inflammatory marker panel of 25 cytokines was used to determine the relationship of BCMs with inflammatory markers and patient’s outcome. All relevant parameters were evaluated in uni- and multivariate survival analysis.ResultsMuscle attenuation (MA)—a well established BCM parameter—is an independent prognostic factor for survival in multivariate analysis (HR 2.25; p = 0.028). Low MA—reflecting a state of cachexia—is also associated with residual tumor after cytoreductive surgery (p = 0.046) and with an unfavorable performance status (p = 0.015). Moreover, MA is associated with Eotaxin and IL-10 out of the 25 cytokine multiplex marker panel in multivariate linear regression analysis (p = 0.021 and p = 0.047, respectively).ConclusionMA—ascertained by routine pre-operative CT—is an independent prognostic parameter in EOC patients. Low MA is associated with the inflammatory, as well as the nutritional component of cachexia. Therefore, the clinical value of pre-operative CT could be enhanced by the assessment of MA.     

Targeting HIV-1 envelope glycoprotein trimers to B cells by using APRIL improves antibody responses

An HIV-1 vaccine remains elusive, in part because various factors limit the quantity and quality of the antibodies raised against the viral envelope glycoprotein complex (Env). We hypothesized that targeting Env vaccines directly to B cells, by fusing them to molecules that bind and activate these cells, would improve Env-specific antibody responses. Therefore, we fused trimeric Env gp140 to A PRoliferation-Inducing Ligand (APRIL), B-cell Activating Factor (BAFF), and CD40 Ligand (CD40L). The Env-APRIL, Env-BAFF, and Env-CD40L gp140 trimers all enhanced the expression of activation-induced cytidine deaminase (AID), the enzyme responsible for inducing somatic hypermutation, antibody affinity maturation, and antibody class switching. They also triggered IgM, IgG, and IgA secretion from human B cells in vitro. The Env-APRIL trimers induced higher anti-Env antibody responses in rabbits, including neutralizing antibodies against tier 1 viruses. The enhanced Env-specific responses were not associated with a general increase in total plasma antibody concentrations, indicating that the effect of APRIL was specific for Env. All the rabbit sera raised against gp140 trimers, irrespective of the presence of CD40L, BAFF, or APRIL, recognized trimeric Env efficiently, whereas sera raised against gp120 monomers did not. The levels of trimer-binding and virus-neutralizing antibodies were strongly correlated, suggesting that gp140 trimers are superior to gp120 monomers as immunogens. Targeting and activating B cells with a trimeric HIV-1 Env-APRIL fusion protein may therefore improve the induction of humoral immunity against HIV-1.     

Complex phytohormone responses during the cold acclimation of two wheat cultivars differing in cold tolerance, winter Samanta and spring Sandra

Hormonal changes accompanying the cold stress (4°C) response that are related to the level of frost tolerance (FT; measured as LT50) and the content of the most abundant dehydrin, WCS120, were compared in the leaves and crowns of the winter wheat (Triticum aestivum L.) cv. Samanta and the spring wheat cv. Sandra. The characteristic feature of the alarm phase (1 day) response was a rapid elevation of abscisic acid (ABA) and an increase of protective proteins (dehydrin WCS120). This response was faster and stronger in winter wheat, where it coincided with the downregulation of bioactive cytokinins and auxin as well as enhanced deactivation of gibberellins, indicating rapid suppression of growth. Next, the ethylene precursor aminocyclopropane carboxylic acid was quickly upregulated. After 3-7 days of cold exposure, plant adaptation to the low temperature was correlated with a decrease in ABA and elevation of growth-promoting hormones (cytokinins, auxin and gibberellins). The content of other stress hormones, i.e., salicylic acid and jasmonic acid, also began to increase. After prolonged cold exposure (21 days), a resistance phase occurred. The winter cultivar exhibited substantially enhanced FT, which was associated with a decline in bioactive cytokinins and auxin. The inability of the spring cultivar to further increase its FT was correlated with maintenance of a relatively higher cytokinin and auxin content, which was achieved during the acclimation period.     

Geographic variation in the habitat preference of a scarce predatory insect: evolutionary and conservation perspectives

1. While there has been considerable focus on prey occurrence as a factor determining the habitat preference of predators, the roles of other factors related to the habitat are less well characterised. 2. In aphidophagous ladybird beetles (Coleoptera: Coccinellidae), a number of species are more restricted in the habitats in which they live than are their prey. A number of such ladybirds appear to show geographic variation in habitat preference. 3. To better understand these phenomena, this study considered geographic variation in habitat preference in one such species, the 5-spot ladybird Coccinella quinquepunctata. Because of this ladybird's scarcity, a combination of over 20 years' observations, habitat surveys and online data was used to reach the study's conclusions. 4. The data collected indicate that the ladybird is specialised in pioneer habitats close to water, but broadens its range to non-riverine pioneer habitats in north-west continental Europe, where it is likely that a damper (micro)climate allows it to do so. Thus, microclimatic factors appear to be important in determining the habitat of this and probably other predators that are not constrained by prey occurrence. 5. Although threatened by river management elsewhere, in north-western Europe, this species clearly benefits from human activity, which creates many of the disturbed habitats it colonises there. This finding provides further support for the contention that many ladybirds are net beneficiaries of human influence, although they are often characterised as threatened.     

Community- Weighted Mean Plant Traits Predict Small Scale Distribution of Insect Root Herbivore Abundance

Small scale distribution of insect root herbivores may promote plant species diversity by creating patches of different herbivore pressure. However, determinants of small scale distribution of insect root herbivores, and impact of land use intensity on their small scale distribution are largely unknown. We sampled insect root herbivores and measured vegetation parameters and soil water content along transects in grasslands of different management intensity in three regions in Germany. We calculated community-weighted mean plant traits to test whether the functional plant community composition determines the small scale distribution of insect root herbivores. To analyze spatial patterns in plant species and trait composition and insect root herbivore abundance we computed Mantel correlograms. Insect root herbivores mainly comprised click beetle (Coleoptera, Elateridae) larvae (43%) in the investigated grasslands. Total insect root herbivore numbers were positively related to community-weighted mean traits indicating high plant growth rates and biomass (specific leaf area, reproductive- and vegetative plant height), and negatively related to plant traits indicating poor tissue quality (leaf C/N ratio). Generalist Elaterid larvae, when analyzed independently, were also positively related to high plant growth rates and furthermore to root dry mass, but were not related to tissue quality. Insect root herbivore numbers were not related to plant cover, plant species richness and soil water content. Plant species composition and to a lesser extent plant trait composition displayed spatial autocorrelation, which was not influenced by land use intensity. Insect root herbivore abundance was not spatially autocorrelated. We conclude that in semi-natural grasslands with a high share of generalist insect root herbivores, insect root herbivores affiliate with large, fast growing plants, presumably because of availability of high quantities of food. Affiliation of insect root herbivores with large, fast growing plants may counteract dominance of those species, thus promoting plant diversity.     

Species specific responses of common grassland plants to a generalist root herbivore (Agriotes spp. larvae)

Insect root herbivores can alter plant community structure by affecting the competitive ability of single plants. Our study aims at increasing knowledge on the impact of click beetle larvae (Elateridae, genus Agriotes) on grassland plant communities, by determining biomass responses as well as responses of the arbuscular mycorrhizal fungi (AMF) symbiosis to this widespread generalist root herbivore for eight common grassland plant species (Festuca rubra, Holcus lanatus, Poa pratensis, Achillea millefolium, Plantago lanceolata, Veronica arvensis, Medicago lupulina, Trifolium repens), belonging to three functional groups (grasses, herbs, legumes).The presence of larvae in the rhizosphere of individual plants had an overall negative effect on root biomass, which varied in degree between plant species, with more root biomass being removed from larger root systems. The effect of larvae on shoot biomass, total plant biomass and shoot/root ratio also differed in strength between plant species. Relative changes in root and total plant biomass ranged from a 71% and 55% loss, respectively, in V. arvensis to an 11% and 1% increase in T. repens, but were not related to root- or plant size. Root colonization by AMF and the length of extraradical AMF hyphae were not affected by larvae. The plant's functional group did not determine the response of the plant to feeding by larvae. Growth of larvae was positively correlated with root biomass, but did not depend on plant species or group identity.The results confirm the generalist nature of Agriotes spp. larvae, which depend on sufficient root quantity and are likely to feed most on those plant species whose roots are most abundant in their habitat. Their effect on the plant community may be generated through the ability of the respective plant species to cope with the herbivore damage, with tolerances being plant species rather than plant group specific.     

Acceleration of mass transfer in methane-producing loop reactors

Gas bubbles entrapped in methanogenic granules subjected to hydrostatic pressure oscillations during recirculation in loop reactors will induce intraparticle liquid flows, and thereby enhance mass transfer in excess of diffusion. This breathing particle concept was clearly demonstrated in a well defined inorganic model system. The experimental results could be described satisfactory with a structured mathematical model, while a 30% improvement is predicted for methanogenic loop reactors as compared to constant pressure systems. It is concluded that acceleration of mass transfer in gas-producing systems offers challenging perspectives for both heterogeneous catalysis and biological fermentations.