Solubility and stability of sterigmatocystin in aqueous solutions

Mycotoxin Research - In the present work we studied the ability of phosphate buffer to solubize sterigmatocystin (ST) at different pH values. We observed a higher solubility of ST at acid pH...     

Keepers of maize in Chiapas,Mexico

This study concerns the knowledge and selection of biological diversity of maize (Zea mays) within its center of domestication in Mesoamerica. Maize farmers in central Chiapas of Southern México keep local varieties (landraces) belonging to six races and four race mixtures. Fifteen local varieties are recognized. In spite of widespread adoption of a modern, high yielding variety, maize farmers continue to select local varieties for specific soils and because of agronomic and use criteria. Farmers maintain maize varieties primarily through seed selection. Spatial and temporal separation do not seem sufficient to maintain varieties. The management of improved varieties can lead from a uniform population to a heterogeneous one as hybridization with local maize populations occurs.     

Heat tolerance of marine ectotherms in a warming Antarctica

Global warming is affecting the Antarctic continent in complex ways. Because Antarctic organisms are specialized to living in the cold, they are vulnerable to increasing temperatures, although quantitative analyses of this issue are currently lacking. Here we compiled a total of 184 estimates of heat tolerance belonging to 39 marine species and quantified how survival is affected concomitantly by the intensity and duration of thermal stress. Species exhibit thermal limits displaced toward colder temperatures, with contrasting strategies between arthropods and fish that exhibit low tolerance to acute heat challenges, and brachiopods, echinoderms, and molluscs that tend to be more sensitive to chronic exposure. These differences might be associated with mobility. A dynamic mortality model suggests that Antarctic organisms already encounter temperatures that might be physiologically stressful and indicate that these ecological communities are indeed vulnerable to ongoing rising temperatures.     

Cryptophytes: An emerging algal group in the rapidly changing Antarctic Peninsula marine environments

The western Antarctic Peninsula (WAP) is a climatically sensitive region where foundational changes at the basis of the food web have been recorded; cryptophytes are gradually outgrowing diatoms together with a decreased size spectrum of the phytoplankton community. Based on a 11-year (2008–2018) in-situ dataset, we demonstrate a strong coupling between biomass accumulation of cryptophytes, summer upper ocean stability, and the mixed layer depth. Our results shed light on the environmental conditions favoring the cryptophyte success in coastal regions of the WAP, especially during situations of shallower mixed layers associated with lower diatom biomass, which evidences a clear competition or niche segregation between diatoms and cryptophytes. We also unravel the cryptophyte photo-physiological niche by exploring its capacity to thrive under high light stress normally found in confined stratified upper layers. Such conditions are becoming more frequent in the Antarctic coastal waters and will likely have significant future implications at various levels of the marine food web. The competitive advantage of cryptophytes in environments with significant light level fluctuations was supported by laboratory experiments that revealed a high flexibility of cryptophytes to grow in different light conditions driven by a fast photo-regulating response. All tested physiological parameters support the hypothesis that cryptophytes are highly flexible regarding their growing light conditions and extremely efficient in rapidly photo-regulating changes to environmental light levels. This plasticity would give them a competitive advantage in exploiting an ecological niche where light levels fluctuate quickly. These findings provide new insights on niche separation between diatoms and cryptophytes, which is vital for a thorough understanding of the WAP marine ecosystem.     

Influence of plant domestication on plant-pollinator interactions: Floral attributes and floral visitor communities in wild and cultivated squash plants

Premise

Domestication of plant species results in phenotypic modifications and changes in biotic interactions. Most studies have compared antagonistic plant-herbivore interactions of domesticated plants and their wild relatives, but little attention has been given to how domestication influences plant-pollinator interactions. Floral attributes and interactions of floral visitors were compared between sister taxa of the genus Cucurbita (Cucurbitaceae), the domesticated C. moschata, C. argyrosperma ssp. argyrosperma and its wild progenitor C. argyrosperma ssp. sororia in the place of origin.

Methods

We conducted univariate and multivariate analyses to compare floral morphological traits and analyzed floral reward (nectar and pollen) quantity and quality between flowers of wild and domesticated Cucurbita taxa. Staminate and pistillate flowers of all three taxa were video recorded, and visitation and behavior of floral visitors were registered and analyzed.

Results

Most floral morphological characteristics of flowers of domesticated taxa were larger in both staminate and pistillate flowers. Staminate and pistillate flowers presented distinct correlations between floral traits and integration indices between domesticated and wild species. Additionally, pollen quantity and protein to lipid ratio were greater in domesticated species. Cucurbit pollen specialists, Eucera spp., had the highest probability of visit for all Cucurbita taxa.

Conclusions

We provide evidence that floral traits of domesticated and wild Cucurbita species experienced different selection pressures. Domesticated Cucurbita species may have more resources invested towards floral traits, thereby increasing attractiveness to pollinators and potentially plant reproductive success. Wild ancestor plant populations should be conserved in their centers of origin to preserve plant-pollinator interactions.     

Changes in the urea concentration during controlled wine aging by two “flor” veil-forming yeasts

Summary Contents of arginine, ornithine, urea and ammonia in wine were monitored during aging process by two flor veil-forming yeast strains. The patterns of yeast growth were different for the two strains studied. Urea excretion and uptake were dependent on yeast strain, so that finished wines showed different concentrations of urea. The effect of limited aeration was also investigated for Saccharomyces cerevisiae var. capensis. The results indicated that aeration promoted yeast growth in veil, thus reducing urea concentration until its exhaustion in wine.     

Changes in the intracellular concentrations of the adenosine phosphates and nicotinamide adenine dinucleotides ofSaccharomyces cerevisiae during batch fermentation

Significant changes in the intracellular concentrations of adenosine phosphates and nicotinamide adenine dinucleotides were observed during fermentation of grape must by three different strains ofSaccharomyces cerevisiae: S. cerevisiae var.cerevisiae, a typical fermentative yeast strain and two flor-veil-forming strains,S. cerevisiae var.bayanus andS. cerevisiae var.capensis. The intracellular concentration of ATP was always higher inS. cerevisiae var.cerevisiae than in the flor-veil-forming strains. NAD⁺ and NADP⁺ concentrations decreased at faster rates in the flor-veil-forming yeasts than in the other yeast but NADH concentration was the same in all yeasts for the first 10 days of fermentation. NADPH concentration was always lower inS. cerevisiae var.cerevisiae than in the other yeasts and this yeast also showed higher rates of growth and fermentation during the early stages of the fermentation and the presence of non-viable cells at the end of fermentation. In contrast, the flor-veil-forming strains maintained growth and fermentation capabilities for a relatively long time and viable cells were present throughout the entire fermentation process (31 days).The authors are with the Department of Microbiology, Faculty of Sciences, University of Cordoba, Avda. San Alberto Magno s/n, 14004-Córdoba, Spain     

Binding, activation, and solubilization of the Ca2+-ATPase from sarcoplasmic reticulum by nonionic detergents

Interactions between delipidated Ca2+-ATPase from sarcoplasmic reticulum and four nonionic detergents--dodecyl octaoxyethyleneglycol monoether (C12E8), Triton X-100, Brij 58, and Brij 35--were characterized with respect to activation of ATPase activity, binding, and solubilization. C12E8 and Triton X-100 activated the delipidated ATPase to at least 80% of the original activity at the critical micelle concentrations (CMCs), whereas Brij 58 and Brij 35 activated no more than 10% of the original activity. The inability of Brij 58 and Brij 35 to activate the delipidated enzyme was probably a result of reduced binding of these detergents below the CMCs; both detergents exhibited a sixteenfold reduction in binding at the CMC compared with C12E8. The two Brij detergents were also unable to solubilize the delipidated enzyme and form monomers, as determined by sedimentation experiments. Thus the reduced binding levels of these detergents may result from an inability to overcome protein/protein interactions in the delipidated preparation. However, the Brij detergents were capable of solubilizing active enzyme from membrane vesicles, although with lower efficiency than C12E8 and Triton X-100. These results suggest that Brij 58 and 35 may be useful for solubilization of membrane proteins without disrupting protein/protein interactions, while Triton X-100 and C12E8 are more useful when bulk solubilization is the goal.     

Air-borne fungi in the air of Barcelona (Spain). III. The genus Aspergillus link

During a survey on the presence of species of the genusAspergillus in the air of the city of Barcelona (Spain), the following species were identified:Aspergillus flavus Link,A. niger van Tieghem,A. fumigatus Fresenius,A. clavatus Desmazières,A. terreus Thorn,A. chevalieri (Mang.) Thomet Church,A. niveus Bloch, emend. Thomet Church,A. ochraceus Wilhelm,A. versicolor (Vuillemin) Tiraboschi, andA. amstelodami (Mang.) Churchet Thom.     

Air-borne fungi in the air of Barcelona (Spain). IV. Various isolated genera

During a two-year survey on the air-borne fungi in the atmosphere of Barcelona (Spain), the following genera were isolated in decreasing order: Aureobasidium, Rhizopus, Mucor, Arthrinium, Phoma, Fusarium, Trichoderma, and Botrytis.