Morphogenesis control in Candida albicans and Candida dubliniensis through signaling molecules produced by planktonic and biofilm cells

Morphogenesis control by chemical signaling molecules is beginning to be highlighted in Candida biology. The present study focuses on morphogenic compounds produced in situ by Candida albicans and Candida dubliniensis during planktonic and biofilm growth that may at least partially substantiate the effect promoted by supernatants in morphogenesis. For both species, planktonic versus biofilm supernatants were analyzed by headspace-solid-phase microextraction and gas chromatography-mass spectrometry. Both planktonic cells and biofilm supernatants of C. albicans and C. dubliniensis contained isoamyl alcohol, 2-phenylethanol, 1-dodecanol, E-nerolidol, and E,E-farnesol. Alcohol secretion profiles were species, culture mode, and growth time specific. The addition of exogenous alcohols to the cultures of both species inhibited the morphological transition from the yeast to the filamentous form by up to 50%. The physiological role of these alcohols was put to evidence by comparing the effects of a 96-h cultured supernatant with synthetic mixtures containing isoamyl alcohol, 2-phenylethanol, E-nerolidol, and E,E-farnesol at concentrations determined herein. All synthetic mixtures elicited a morphological effect similar to that observed for the corresponding supernatants when used to treat C. albicans and C. dubliniensis cultures, except for the effect of the 96-h C. dubliniensis planktonic supernatant culture on C. albicans. Overall, these results reveal a group of alcohol extracellular signaling molecules that are biologically active with C. albicans and C. dubliniensis morphogenesis.     

Solar radiation and functional traits explain the decline of forest primary productivity along a tropical elevation gradient

One of the major challenges in ecology is to understand how ecosystems respond to changes in environmental conditions, and how taxonomic and functional diversity mediate these changes. In this study, we use a trait‐spectra and individual‐based model, to analyse variation in forest primary productivity along a 3.3 km elevation gradient in the Amazon‐Andes. The model accurately predicted the magnitude and trends in forest productivity with elevation, with solar radiation and plant functional traits (leaf dry mass per area, leaf nitrogen and phosphorus concentration, and wood density) collectively accounting for productivity variation. Remarkably, explicit representation of temperature variation with elevation was not required to achieve accurate predictions of forest productivity, as trait variation driven by species turnover appears to capture the effect of temperature. Our semi‐mechanistic model suggests that spatial variation in traits can potentially be used to estimate spatial variation in productivity at the landscape scale.     

Impact of magnetic nanofillers in the swelling and release properties of κ-carrageenan hydrogel nanocomposites

Natural polysaccharides such as κ-carrageenan are an important class of biomaterials for drug delivery. The incorporation of magnetic nanoparticles in polysaccharide hydrogels is currently being explored as a strategy to confer to the hydrogels novel functionalities valuable for specific bio-applications. Within this context, κ-carrageenan magnetic hydrogel nanocomposites have been prepared and the effect of magnetic (Fe₃O₄) nanofillers in the swelling of the hydrogels and in the release kinetics and mechanism of a model drug (methylene blue) has been investigated. In vitro release studies demonstrated the applicability of the composites in sustained drug release. The mechanism controlling the release seems to be determined by the strength of the gel network and the extent of gel swelling, both being affected by the incorporation of nanofillers. Furthermore, it was demonstrated that the release rate and profile could be tailored using variable Fe₃O₄ nanoparticles load. Thus, this seems to be a promising strategy for the development of drug delivery systems with tailored released behavior.     

Intermodal transfer from a visual to an auditory discrimination using an errorless learning procedure

Errorless learning is a technique developed by Terrace [Terrace, H.S., 1963a. Discrimination training with and without “errors”. J. Exp. Anal. Behav. 6, 1-27] to train stimulus discriminations with few or no errors. In the first replication of the original findings, errorless learning was also shown to transfer successfully between two visual discriminations without errors [Terrace, H.S., 1963b. Errorless transfer of a discrimination across two continua. J. Exp. Anal. Behav. 6, 223-232]. In the present experiment, we extended the errorless learning procedure to an intermodal transfer, from a discrimination between red and green colors to a discrimination between high and low tones. The pigeons were divided into two groups: an Experimental Group, which learned both discriminations through errorless learning, and a Control Group, which learned them through trial-and-error. Results showed that pigeons from the Experimental Group learned the red-green discrimination with significantly fewer errors than the Control Group and that errorless learning is effective in transferring from a visual to an auditory discrimination.     

Community composition has greater impact on the functioning of marine phytoplankton communities than ocean acidification

Ecosystem functioning is simultaneously affected by changes in community composition and environmental change such as increasing atmospheric carbon dioxide (CO₂) and subsequent ocean acidification. However, it largely remains uncertain how the effects of these factors compare to each other. Addressing this question, we experimentally tested the hypothesis that initial community composition and elevated CO₂ are equally important to the regulation of phytoplankton biomass. We full‐factorially exposed three compositionally different marine phytoplankton communities to two different CO₂ levels and examined the effects and relative importance (ω²) of the two factors and their interaction on phytoplankton biomass at bloom peak. The results showed that initial community composition had a significantly greater impact than elevated CO₂ on phytoplankton biomass, which varied largely among communities. We suggest that the different initial ratios between cyanobacteria, diatoms, and dinoflagellates might be the key for the varying competitive and thus functional outcome among communities. Furthermore, the results showed that depending on initial community composition elevated CO₂ selected for larger sized diatoms, which led to increased total phytoplankton biomass. This study highlights the relevance of initial community composition, which strongly drives the functional outcome, when assessing impacts of climate change on ecosystem functioning. In particular, the increase in phytoplankton biomass driven by the gain of larger sized diatoms in response to elevated CO₂ potentially has strong implications for nutrient cycling and carbon export in future oceans.     

Evolutionary Genomics and Adaptive Evolution of the Hedgehog Gene Family (Shh,Ihh and Dhh) in Vertebrates

The Hedgehog (Hh) gene family codes for a class of secreted proteins composed of two active domains that act as signalling molecules during embryo development, namely for the development of the nervous and skeletal systems and the formation of the testis cord. While only one Hh gene is found typically in invertebrate genomes, most vertebrates species have three (Sonic hedgehog – Shh; Indian hedgehog – Ihh; and Desert hedgehog – Dhh), each with different expression patterns and functions, which likely helped promote the increasing complexity of vertebrates and their successful diversification. In this study, we used comparative genomic and adaptive evolutionary analyses to characterize the evolution of the Hh genes in vertebrates following the two major whole genome duplication (WGD) events. To overcome the lack of Hh-coding sequences on avian publicly available databases, we used an extensive dataset of 45 avian and three non-avian reptilian genomes to show that birds have all three Hh paralogs. We find suggestions that following the WGD events, vertebrate Hh paralogous genes evolved independently within similar linkage groups and under different evolutionary rates, especially within the catalytic domain. The structural regions around the ion-binding site were identified to be under positive selection in the signaling domain. These findings contrast with those observed in invertebrates, where different lineages that experienced gene duplication retained similar selective constraints in the Hh orthologs. Our results provide new insights on the evolutionary history of the Hh gene family, the functional roles of these paralogs in vertebrate species, and on the location of mutational hotspots.     

Charged surfactants induce a non‐fibrillar aggregation pathway of amyloid‐beta peptide

The amyloid β‐peptide with a sequence of 42 amino acids is the major constituent of extracellular amyloid deposits in Alzheimer's disease plaques. The control of the peptide self‐assembly is difficult to achieve because the process is fast and is affected by many variables. In this paper, we describe the effect of different charged and non‐charged surfactants on Aβ_(1‐42) fibrillation to define common alternate aggregation pathways. The characterization of the peptide‐surfactant interactions by ultra‐structural analysis, thioflavin T assay and secondary structure analysis, suggested that charged surfactants interact with Aβ_(1‐42) through electrostatic interactions. Charged micelles slow down the aggregation process and stabilize the peptide in the oligomeric state, whereas non‐charged surfactants promote the Aβ_(1‐42) fibril formation. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Diet of the Iberian hare (Lepus granatensis) in a mountain ecosystem

The diet of the Iberian hare (Lepus granatensis) was studied through microhistological pellet analysis in two areas from a mountain ecosystem in Central Portugal. Fecal pellets were collected monthly in 24 plots spatially distributed throughout the two study areas. For each period, a sample of 15 to 20 pellets was milled and 400 epidermal fragments were identified, by comparison with a reference collection. A wide range of plant species was observed in hare’s diet. Grasses represent the basis of the Iberian hare diet, with frequencies always higher than 50% in both study areas (annual average = 69.98%). Most of the 35 species of grasses assembled for the reference collection (91.43%) were identified in the pellets. Nevertheless, only six of these were consumed in proportions greater than 5%, being Anthoxanthum odoratum, Secale cereale and Agrostis spp. the species ingested in higher frequencies. The rate of grasses consumption reached 80.69% in winter but decreased in summer to around 55%. In this season, a concurrent rise in the ingestion of other plant groups, like herbs and shrubs, and of plant inflorescences was observed. This work provides the first results on the Iberian hare’s diet on mountain ecosystems, and suggests that the Iberian hare diet in a mountain ecosystem is similar to the observed in L. europaeus and L. timidus.     

Survival of freeze-dried Lactobacillus plantarum and Lactobacillus rhamnosus during storage in the presence of protectants

No significant differences were observed in the viability of Lactobacillus plantarum and Lactobacillus rhamnosus cells during freeze-drying in the presence or absence of inositol, sorbitol, fructose, trehalose, monosodium glutamate and propyl gallate. However, survival was higher during storage when drying took place in the presence of these compounds. Sorbitol produced more significant effects than the other compounds toward maintaining viability of freeze-dried L. plantarum and L. rhamnosus.