Dynamics of CRISPR Loci in Microevolutionary Process of Yersinia pestis Strains

The potential use of CRISPR loci genotyping to elucidate population dynamics and microevolution of 146 Yersinia pestis strains from different biovars and locations was investigated in this work. The majority of strains from the Orientalis biovar presented specific spacer arrays, allowing for the establishment of a CRISPR signature for their respective isolates. Twenty-one new spacers were found in the Y. pestis strains from plague foci in Brazil. Ninety-three (64%) strains were grouped in the G1 genotype, whereas the others were distributed in 35 genotypes. This study allowed observing a microevolutionary process in a group of Y. pestis isolated from Brazil. We also identified specific genotypes of Y. pestis that were important for the establishment of the bacteria in plague foci in Brazil. The data have provided supporting evidence for the diversity and dynamics of CRISPR loci present in the genome of Y. pestis strains from plague foci in Brazil.     

Modeling of non-covalent complexes of the cell-penetrating peptide CADY and its siRNA cargo

CADY is a cell-penetrating peptide spontaneously making non-covalent complexes with Short interfering RNAs (siRNAs) in water. Neither the structure of CADY nor that of the complexes is resolved. We have calculated and analyzed 3D models of CADY and of the non-covalent CADY–siRNA complexes in order to understand their formation and stabilization. Data from the ab initio calculations and molecular dynamics support that, in agreement with the experimental data, CADY is a polymorphic peptide partly helical. Taking into consideration the polymorphism of CADY, we calculated and compared several complexes with peptide/siRNA ratios of up to 40. Four complexes were run by using molecular dynamics. The initial binding of CADYs is essentially due to the electrostatic interactions of the arginines with siRNA phosphates. Due to a repetitive arginine motif (XLWR(K)) in CADY and to the numerous phosphate moieties in the siRNA, CADYs can adopt multiple positions at the siRNA surface leading to numerous possibilities of complexes. Nevertheless, several complex properties are common: an average of 14 ± 1 CADYs is required to saturate a siRNA as compared to the 12 ± 2 CADYs experimentally described. The 40 CADYs/siRNA that is the optimal ratio for vector stability always corresponds to two layers of CADYs per siRNA. When siRNA is covered by the first layer of CADYs, the peptides still bind despite the electrostatic repulsion. The peptide cage is stabilized by hydrophobic CADY–CADY contacts thanks to CADY polymorphism. The analysis demonstrates that the hydrophobicity, the presence of several positive charges and the disorder of CADY are mandatory to make stable the CADY–siRNA complexes.     

Les diatomees dans l'upwelling de Cabo Frio (Bresil): liste d'especes et etude ecologique

The diatoms in the Cabo Frio (Brazil) upwelling: check listand ecological study. A qualitative and quantitative study onthe diatoms from the Cabo Frio area was made and a check listproduced. Sampling was carried out over one year at an anchoragestation in the upwelling zone. Data were analysed by means ofa multivariate statistical method, in order to show the mainsynecological aspects of the diatom populations. Diatoms dominatein most samples, except in the Brazil current water where dinoflagellatesare dominant, and where there is a poor population of thermophilicdiatoms. Recently upwelled water has a poor phytoplankton composedof epiphytic and benthic species; these are substituted by intenseblooms of neritic and opportunist diatoms when the temperaturerises. The annual distribution of the diatoms accompanies theoccurrence of upwelling. The vertical thermal gradient or waterstability is the most important factor affecting the specificcomposition and distribution of the diatom communities.     

Characterization of a chondrocyte primary culture from rib cartilage of the rat

In order to standardize and to characterize a chondrocyte primary culture, cells from rat rib resting cartilage were used. High yield (0.99 +/- 0.18 x 10(6) cells/rat) and viability (91.76%) of costal cartilage cells was reached by enzymatic digestion with collagenase. The cells were cultivated in Dulbecco's medium (DME) supplemented with 10%. Heat inactivated newborn calf serum, at 37 degrees under humidified atmosphere of 5% CO2 in air. Two or three days after plating, the cells were attached to the surface of tissue culture weel, and began dividing. Adhesion was independent of plating density. The doubling time of cell population was found to be 23.19 hours. The cells became a monolayer and required easy maintenance. The results support the contention that rat costal cartilage is a good source of chondrocytes for primary culture cells experiments.     

Magnetosome magnetite biomineralization in a flagellated protist: evidence for an early evolutionary origin for magnetoreception in eukaryotes

The most well-recognized magnetoreception behaviour is that of the magnetotactic bacteria (MTB), which synthesize membrane-bounded magnetic nanocrystals called magnetosomes via a biologically controlled process. The magnetic minerals identified in prokaryotic magnetosomes are magnetite (Fe₃O₄) and greigite (Fe₃S₄). Magnetosome crystals, regardless of composition, have consistent, species-specific morphologies and single-domain size range. Because of these features, magnetosome magnetite crystals possess specific properties in comparison to abiotic, chemically synthesized magnetite. Despite numerous discoveries regarding MTB phylogeny over the last decades, this diversity is still considered underestimated. Characterization of magnetotactic microorganisms is important as it might provide insights into the origin and establishment of magnetoreception in general, including eukaryotes. Here, we describe the magnetotactic behaviour and characterize the magnetosomes from a flagellated protist using culture-independent methods. Results strongly suggest that, unlike previously described magnetotactic protists, this flagellate is capable of biomineralizing its own anisotropic magnetite magnetosomes, which are aligned in complex aggregations of multiple chains within the cell. This organism has a similar response to magnetic field inversions as MTB. Therefore, this eukaryotic species might represent an early origin of magnetoreception based on magnetite biomineralization. It should add to the definition of parameters and criteria to classify biogenic magnetite in the fossil record.     

Endangered globose cactus Melocactus lanssensianus P. J. Braun depends on lizards for effective seed dispersal in the Brazilian Caatinga

Effective seed dispersal is essential to plant reproductive success. In this study, we evaluated the fruiting phenology, fruit traits, and seed dispersal of the endangered globose cactus Melocactus lanssensianus in the Brazilian Caatinga over 1-year period. We carried out monthly phenological monitoring, focal observations, and germination experiments, to identify the effective seed dispersers of this cactus. M. lanssensianus exhibited a continuous, non-seasonal fruiting pattern, with peaks during both the dry and rainy seasons. We observed seed dispersal by Tropidurus semitaeniatus and T. hispidus lizards. In 116 h of focal observations, lizards made 76 visits during different times of day, with a mean dispersal distance of 5 m. Both lizard species showed more frugivory interactions in the dry season, with peak visits in water-stressed months. We collected 132 intact and viable seeds from 29 fecal samples, specifically from T. semitaeniatus (N?=?20 scats; 122 seeds) and from T. hispidus (N?=?9 scats; 10 seeds). Germination experiments with seeds consumed by T. semitaeniatus, washed seeds and control seeds revealed that 85% of seeds found in T. semitaeniatus feces germinated compared to 41% of the control seeds. Frequency, pattern of visits and germination rates indicate T. semitaeniatus is an effective seed disperser of M. lanssensianus. Continuous production of fleshy fruits and environmental conditions of the Caatinga ecosystem favor the close dependent mutualistic interaction reported here.

     

The scientific value of Amazonian protected areas

Protected areas (PAs) are under increasing pressure to demonstrate their broader value and contribution to society. Scientific research and associated knowledge production comprise one such value, which has received relatively little attention in the academic literature. Here, we use the Amazon region as a case study to quantify scientific knowledge production (as measured by scientific publications in peer-reviewed journals) in PAs and identify the main biophysical, geographical and social characteristics that influence such production. We adopt a multi-model inference approach with an innovative hurdle regression model to independently assess the factors influencing the presence of research and the number of studies in PAs. Our results indicate a highly skewed pattern of scientific production, with many PAs with few or no associated scientific articles. Larger, older and more highly protected PAs in Ecuador and Peru were most likely to have scientific production, while time since first publication was most strongly associated with the number of publications from a PA. These findings provide important insights that could be used to support and strengthen policy aimed at increasing the value of Amazonian protected areas for scientific research.     

Piracetam inhibits the lipid-destabilising effect of the amyloid peptide Aβ C-terminal fragment

Amyloid peptide (Aβ) is a 40/42-residue proteolytic fragment of a precursor protein (APP), implicated in the pathogenesis of Alzheimer's disease. The hypothesis that interactions between Aβ aggregates and neuronal membranes play an important role in toxicity has gained some acceptance. Previously, we showed that the C-terminal domain (e.g. amino acids 29-42) of Aβ induces membrane permeabilisation and fusion, an effect which is related to the appearance of non-bilayer structures. Conformational studies showed that this peptide has properties similar to those of the fusion peptide of viral proteins i.e. a tilted penetration into membranes. Since piracetam interacts with lipids and has beneficial effects on several symptoms of Alzheimer's disease, we investigated in model membranes the ability of piracetam to hinder the destabilising effect of the Aβ 29-42 peptide. Using fluorescence studies and ³¹P and ²H NMR spectroscopy, we have shown that piracetam was able to significantly decrease the fusogenic and destabilising effect of Aβ 29-42, in a concentration-dependent manner. While the peptide induced lipid disorganisation and subsequent negative curvature at the membrane-water interface, the conformational analysis showed that piracetam, when preincubated with lipids, coats the phospholipid headgroups. Calculations suggest that this prevents appearance of the peptide-induced curvature. In addition, insertion of molecules with an inverted cone shape, like piracetam, into the outer membrane leaflet should make the formation of such structures energetically less favourable and therefore decrease the likelihood of membrane fusion.