Timing and abundance as key mechanisms affecting trophic interactions in variable environments

Climatic changes are disrupting otherwise tight trophic interactions between predator and prey. Most of the earlier studies have primarily focused on the temporal dimension of the relationship in the framework of the match–mismatch hypothesis. This hypothesis predicts that predator's recruitment will be high if the peak of the prey availability temporally matches the most energy‐demanding period of the predators breeding phenology. However, the match–mismatch hypothesis ignores the level of food abundance while this can compensate small mismatches. Using a novel time‐series model explicitly quantifying both the timing and the abundance component for trophic relationships, we here show that timing and abundance of food affect recruitment differently in a marine (cod/zooplankton), a marine–terrestrial (puffin/herring) and a terrestrial (sheep/vegetation) ecosystem. The quantification of the combined effect of abundance and timing of prey on predator dynamics enables us to come closer to the mechanisms by which environment variability may affect ecological systems.     

Process monitoring of virus-like particle reassembly by diafiltration with UV/Vis spectroscopy and light scattering

Virus-like particles (VLPs) have shown great potential as biopharmaceuticals in the market and in clinics. Nonenveloped, in vivo assembled VLPs are typically disassembled and reassembled in vitro to improve particle stability, homogeneity, and immunogenicity. At the industrial scale, cross-flow filtration (CFF) is the method of choice for performing reassembly by diafiltration. Here, we developed an experimental CFF setup with an on-line measurement loop for the implementation of process analytical technology (PAT). The measurement loop included an ultraviolet and visible (UV/Vis) spectrometer as well as a light scattering photometer. These sensors allowed for monitoring protein concentration, protein tertiary structure, and protein quaternary structure. The experimental setup was tested with three Hepatitis B core Antigen (HBcAg) variants. With each variant, three reassembly processes were performed at different transmembrane pressures (TMPs). While light scattering provided information on the assembly progress, UV/Vis allowed for monitoring the protein concentration and the rate of VLP assembly based on the microenvironment of Tyrosine-132. VLP formation was verified by off-line dynamic light scattering (DLS) and transmission electron microscopy (TEM). Furthermore, the experimental results provided evidence of aggregate-related assembly inhibition and showed that off-line size-exclusion chromatography does not provide a complete picture of the particle content. Finally, a Partial-Least Squares (PLS) model was calibrated to predict VLP concentrations in the process solution. values of 0.947–0.984 were reached for the three HBcAg variants. In summary, the proposed experimental setup provides a powerful platform for developing and monitoring VLP reassembly steps by CFF.     

Prescribing diatom morphology: toward genetic engineering of biological nanomaterials

The formation of inorganic materials with complex form is a widespread biological phenomenon (biomineralization). Among the most spectacular examples of biomineralization is the production by diatoms (a group of eukaryotic microalgae) of intricately nanopatterned to micropatterned cell walls made of silica (SiO2). Understanding the molecular mechanisms of diatom silica biomineralization is not only a fundamental biological problem, but also of great interest in materials engineering, as the biological self-assembly of three-dimensional (3D) inorganic nanomaterials has no man-made analog. Recently, insight into the molecular mechanism of diatom silica formation has been obtained by structural and functional analysis of biomolecules that are involved in this process. Furthermore, the rapid development of diatom molecular genetics has provided new tools for investigating the silica forming machinery of diatoms and for manipulating silica biogenesis. This has opened the door for the production, through genetic engineering, of unique 3D nanomaterials with designed structures and functionalities.     

New insights into the butyric acid metabolism of Clostridium acetobutylicum

Biosynthesis of acetone and n-butanol is naturally restricted to the group of solventogenic clostridia with Clostridium acetobutylicum being the model organism for acetone-butanol-ethanol (ABE) fermentation. According to limited genetic tools, only a few rational metabolic engineering approaches were conducted in the past to improve the production of butanol, an advanced biofuel. In this study, a phosphotransbutyrylase-(Ptb) negative mutant, C. acetobutylicum ptb::int(87), was generated using the ClosTron methodology for targeted gene knock-out and resulted in a distinct butyrate-negative phenotype. The major end products of fermentation experiments without pH control were acetate (3.2?g/l), lactate (4.0?g/l), and butanol (3.4?g/l). The product pattern of the ptb mutant was altered to high ethanol (12.1?g/l) and butanol (8.0?g/l) titers in pH?≥?5.0-regulated fermentations. Glucose fed-batch cultivation elevated the ethanol concentration to 32.4?g/l, yielding a more than fourfold increased alcohol to acetone ratio as compared to the wildtype. Although butyrate was never detected in cultures of C. acetobutylicum ptb::int(87), the mutant was still capable to take up butyrate when externally added during the late exponential growth phase. These findings suggest that alternative pathways of butyrate re-assimilation exist in C. acetobutylicum, supposably mediated by acetoacetyl-CoA:acyl-CoA transferase and acetoacetate decarboxylase, as well as reverse reactions of butyrate kinase and Ptb with respect to previous studies.     

Reliance on head versus eyes in the gaze following of great apes and human infants: the cooperative eye hypothesis

As compared with other primates, humans have especially visible eyes (e.g., white sclera). One hypothesis is that this feature of human eyes evolved to make it easier for conspecifics to follow an individual's gaze direction in close-range joint attentional and communicative interactions, which would seem to imply especially cooperative (mututalistic) conspecifics. In the current study, we tested one aspect of this cooperative eye hypothesis by comparing the gaze following behavior of great apes to that of human infants. A human experimenter "looked" to the ceiling either with his eyes only, head only (eyes closed), both head and eyes, or neither. Great apes followed gaze to the ceiling based mainly on the human's head direction (although eye direction played some role as well). In contrast, human infants relied almost exclusively on eye direction in these same situations. These results demonstrate that humans are especially reliant on eyes in gaze following situations, and thus, suggest that eyes evolved a new social function in human evolution, most likely to support cooperative (mututalistic) social interactions.     

Effects of acorn masting on population dynamics of three forest-dwelling rodent species in Hokkaido,Japan

The effects of the abundance of acorns of the oak, Quercus crispula, on the population dynamics of three rodent species (Apodemus speciosus, A. argenteus, and Clethrionomys rufocanus) were analyzed using time series data (1992–2006). The data were obtained in a forest in northern Hokkaido, Japan, by live trapping rodents and directly counting acorns on the ground. Apodemus speciosus generally increased in abundance following acorn masting. However, the clear effect of acorn abundance was not detected for the other two rodent species. Acorns of Q. crispula contain tannins, which potentially have detrimental effects on herbivores. Apodemus speciosus may reduce the damage caused by acorn tannins with tannin-binding salivary proteins and tannase-producing bacteria, whereas such physiological tolerance to tannins is not known in the other two rodent species. The differences in the effects of acorns between the three species may be due to differences in their physiological tolerance to tannins.     

European springtime temperature synchronises ibex horn growth across the eastern Swiss Alps

Direct effects of climate change on animal physiology, and indirect impacts from disruption of seasonal synchrony and breakdown of trophic interactions are particularly severe in Arctic and Alpine ecosystems. Unravelling biotic from abiotic drivers, however, remains challenging because high‐resolution animal population data are often limited in space and time. Here, we show that variation in annual horn growth (an indirect proxy for individual performance) of 8043 male Alpine ibex (Capra ibex) over the past four decades is well synchronised among eight disjunct colonies in the eastern Swiss Alps. Elevated March to May temperatures, causing premature melting of Alpine snowcover, earlier plant phenology and subsequent improvement of ibex food resources, fuelled annual horn growth. These results reveal dependency of local trophic interactions on large‐scale climate dynamics, and provide evidence that declining herbivore performance is not a universal response to global warming even for high‐altitude populations that are also harvested.     

Meniscofemoral ligaments--structural and material properties

The meniscofemoral ligaments (MFLs) of 28 human cadaveric knees were studied to determine their incidence, structural and material properties. Using the Race–Amis casting method for measurement, the mean cross-sectional area for the anterior MFL (aMFL) was 14.7 mm² (±14.8 mm²) whilst that of the posterior MFL (pMFL) was 20.9 mm² (±11.6 mm²). The ligaments were isolated and tensile tested in a materials testing machine. The mean loads to failure were 300.5 N (±155.0 N) for the aMFL and 302.5 N (±157.9 N) for the pMFL, with elastic moduli of 281 (±239 MPa) and 227 MPa (±128 MPa), respectively. These significant anatomical and material properties suggest a function for the MFL in the biomechanics of the knee, and should be borne in mind when considering hypotheses on MFL function. Such hypotheses include roles for the ligaments in knee stability and guiding meniscal motion.     

Traditional Ecological Knowledge of a Riverine Forest in Turkana, Kenya: Implications for Research and Management

The present study explores traditional ecological knowledge (TEK) of Turkana pastoralists and cultivators in the context of a riverine forest in northern Kenya. The Turkwel River and its floodplain sustain a thick forest, which is used for grazing and extraction of non-timber forest products. However, sedentarisation and agricultural expansion have resulted in localised clear-felling of trees, while river damming has altered the natural flow regime. A series of structured, semi-structured, and group interviews were combined with a botanical inventory in order to assess the relevance of TEK to ecological research and forest conservation. Turkana informants gave 102 vernacular names for the 113 woody species. Of these, 85% had a domestic or pastoral use among the 105 specific uses that were described. Ethnobotanical knowledge was relatively homogenous and not related to age, gender, or source of livelihood. The informants had in-depth knowledge of some key ecological processes. The conceived threats to forest survival were primarily cultivation and permanent settlements, while the effects of river damming and livestock grazing were disputed. A claimed decline in rainfall was confirmed by official data. There is strong evidence that TEK could be used to generate hypotheses for research and to design sustainable conservation strategies. A revised version of the indigenous system of tree management should be incorporated into the official forestry policy in order to resolve future conflicts between pastoralists and cultivators.