Identification of novel DNA fragments and partial sequence of a genomic island specific of Brucella pinnipedialis

Since the 1990s, Brucella strains have been isolated from a wide variety of marine mammals and were recently recognized as two different species, i.e. Brucella pinnipedialis for pinniped isolates and Brucella ceti for cetacean isolates. The aim of this study was to identify specific DNA fragments of marine mammal Brucella strains using a previously described infrequent restriction site-PCR (IRS-PCR) method but with three new couples of restriction enzymes applied on a larger panel of marine mammal Brucella isolates (n=74) and one human isolate from New Zealand likely from marine mammal origin. This study revealed five DNA fragments specific of Brucella strains isolated from marine mammals. Among them two new DNA fragments were specific of B. pinnipedialis but were not detected in hooded seal isolates. DNA fragment I identified in the previous IRS-PCR study and fragment VI of this study were located on a cloned and sequenced 6kb SacI fragment. Its nucleotide sequence revealed that it is likely part of a putative genomic island. Sequence analysis showed that it carries four ORFs coding for putative metabolic functions. Although hooded seal isolates are classified within B. pinnipedialis it was shown in this study that they do not carry this genomic island and this raises the question about their evolutionary history within B. pinnipedialis.     

Root elongation in tropical Eucalyptus plantations: effect of soil water content

? Sustainability of Eucalyptus plantations is often questioned in resource-limited environments, especially in areas characterized by soils with poor nutrient and water holding capacities. Yet, field-based observations of fine root dynamics in relation with the seasonality of rainfall are lacking.

? This study was undertaken on two Eucalyptus stands planted in the Kouilou Region (south-western Congo), which is characterized by a four-month-long dry season. Fine root (less than 2 mm in diameter) dynamics were studied using rhizotron observations of root elongation in the field.

? Fine root elongation rates displayed a seasonal variation in the two stands, with higher elongation rates during the rainy season than during the dry season. Positive and significant correlations were found between fine root elongation rates and soil water content at all depths, but a better correlation was found with soil water content in the deep soil horizon than in the superficial horizons.

? These results suggest that the temporal variations in fine root elongation were related to the seasonality of rainfall, and they were probably associated with seasonal changes in tree water status, carbon assimilation and belowground allocation.

     

Dry-heating makes hen egg white lysozyme an efficient foaming agent and enables its bulk aggregation

Dry-heating is considered to be one of the most promising approaches to improving the functionality of food proteins. It has been shown that even if only minor structural modifications occur during dry-heating, the foaming properties of proteins are highly improved. With the recent results obtained in the field of foam stabilization by nanoparticles or protein aggregates in mind, a study was undertaken on the impact of dry-heating of lysozyme, used as a model protein, on its foaming properties. This work highlighted the fact that dry-heated hen egg white lysozyme simultaneously exhibited enhanced foaming properties and aggregation capacity. Although the conditions that favored bulk aggregation (high ionic strength, pH, treatment duration, and protein concentration) also favored foaming properties, the large bulk aggregates were not essential to obtain the best functionality. It is envisaged that heat-treated lysozyme may self-associate at the air/water interface, stabilizing air bubbles.     

Genetic structure,origin, and connectivity between nesting and foraging areas of hawksbill turtles of the Yucatan Peninsula: A study for conservation and management

相似文献   

Aromatase (P450arom) and 11β-hydroxylase (P45011β) genes are differentially expressed during the sex change process of the protogynous rice field eel, monopterus albus

Steroids are known to play a crucial role in gonadal sex differentiation in many non-mammalian vertebrates, but also in the gonadal sex change of hermaphroditic teleosts. We investigated the expression of two genes encoding key steroidogenic enzymes, i.e., cytochrome P450 aromatase (P450arom) and cytochrome P45011β-hydroxylase (P45011β), during the sex change of the protogynous rice field eel, Monopterus albus. Using RT-PCR with degenerate primers, we cloned rice field eel homologous fragments for both genes (rcP450arom and rcP45011β) as indicated by the high level of homology with P450arom and P45011β sequences from various vertebrates. Gonadal expression of rcP450arom and rcP45011β mRNA levels were then assessed during the sex change by semi-quantitative RT-PCR and a real-time RT-PCR. rcP450arom was predominantly expressed in ovary, much less in ovotestis, and barely in testis. Conversely, P45011β was markedly up-regulated at the onset of testicular development. These findings underline that regulation of steroidogenesis is an important process in the sex change of protogynous rice field eel, and they clearly indicate that the concomitant down-regulation of P450arom and up-regulation of P45011β are of pivotal importance to the sex change of this species.     

Nutrient cycling in a clonal stand of Eucalyptus and an adjacent savanna ecosystem in Congo: 3. Input–output budgets and consequences for the sustainability of the plantations

Clonal plantations of Eucalyptus have been introduced since 1978 on savanna soils of the coastal plains of Congo. Atmospheric deposition, canopy exchange and transfer through the soil were estimated on the whole rooting depth (6 m) over 3 years, in an experimental design installed in a native savanna and an adjacent 6-year-old Eucalyptus plantation. Complementary measurements after planting the experimental savanna made it possible to establish input–output budgets of nutrients for the whole Eucalyptus rotation and to compare them with the native savanna ecosystem.

In this highly-weathered soil, atmospheric deposits and symbiotic N fixation by a legume species balanced the nutrient budgets in savanna, despite large losses during annual burnings. After afforestation, weeding in the Eucalyptus stands eliminated the leguminous species responsible for a N input by symbiotic fixation of about 20 kg ha⁻¹ year⁻¹. Whereas the budgets of P, K, Ca and Mg were roughly balanced, the current silviculture led to a deficit of about 140 kg N ha⁻¹ in the soil, throughout a 7-year rotation. This deficit was large relative to the pool of total N in the upper soil layer (0–50 cm), which was about 2 t ha⁻¹. Therefore, the sustainability of Congolese plantations will require an increase in N fertilizer inputs over successive rotations to balance the N budget. These results were consistent with field trials of fertilization. Practical consequences of these budgets were identified, in order to: (i) direct field trials of fertilization, (ii) select appropriate methods of soil preparation, weed control and harvest, (iii) highlight the importance of fire prevention in this area, and (iv) support the implementation of field trials aiming at introducing a biological nitrogen fixing understorey in Eucalyptus stands.     

Assessing the effects of climate change on the phenology of European temperate trees

Modelling phenology is crucial to assess the impact of climate change on the length of the canopy duration and the productivity of terrestrial ecosystems. Focusing on six dominant European tree species, the aims of this study were (i) to examine the accuracy of different leaf phenology models to simulate the onset and ending of the leafy season, with particular emphasis on the putative role of chilling to release winter bud dormancy and (ii) to predict seasonal shifts for the 21st century in response to climate warming.Models testing and validation were done for each species considering 2 or 3 years of phenological observations acquired over a large elevational gradient (1500 m range, 57 populations). Flushing models were either based solely on forcing temperatures (1-phase models) or both on chilling and forcing temperatures (2-phases models). Leaf senescence models were based on both temperature and photoperiod.We show that most flushing models are able to predict accurately the observed flushing dates. The 1-phase models are as efficient as 2-phases models for most species suggesting that chilling temperatures are currently sufficient to fully release bud dormancy. However, our predictions for the 21st century highlight that chilling temperature could be insufficient for some species at low elevation. Overall, flushing is expected to advance in the next decades but this trend substantially differed between species (from 0 to 2.4 days per decade). The prediction of leaf senescence appears more challenging, as the proposed models work properly for only two out of four deciduous species, for which senescence is expected to be delayed in the future (from 1.4 to 2.3 days per decade). These trends to earlier spring leafing and later autumn senescence are likely to affect the competitive balance between species. For instance, simulations over the 21st century predict a stronger lengthening of the canopy duration for Quercus petraea than for Fagus sylvatica, suggesting that shifts in the elevational distributions of these species might occur.     

Cytotoxicity,Fractionation and Dereplication of Extracts of the Dinoflagellate Vulcanodinium rugosum,a Producer of Pinnatoxin G

Pinnatoxin G (PnTX-G) is a marine toxin belonging to the class of cyclic imines and produced by the dinoflagellate Vulcanodinium rugosum. In spite of its strong toxicity to mice, leading to the classification of pinnatoxins into the class of “fast-acting toxins”, its hazard for human health has never been demonstrated. In this study, crude extracts of V. rugosum exhibited significant cytotoxicity against Neuro2A and KB cells. IC₅₀ values of 0.38 µg mL⁻¹ and 0.19 µg mL⁻¹ were estimated on Neuro2A cells after only 24 h of incubation and on KB cells after 72 h of incubation, respectively. In the case of Caco-2 cells 48 h after exposure, the crude extract of V. rugosum induced cell cycle arrest accompanied by a dramatic increase in double strand DNA breaks, although only 40% cytotoxicity was observed at the highest concentration tested (5 µg mL⁻¹). However, PnTX-G was not a potent cytotoxic compound as no reduction of the cell viability was observed on the different cell lines. Moreover, no effects on the cell cycle or DNA damage were observed following treatment of undifferentiated Caco-2 cells with PnTX-G. The crude extract of V. rugosum was thus partially purified using liquid-liquid partitioning and SPE clean-up. In vitro assays revealed strong activity of some fractions containing no PnTX-G. The crude extract and the most potent fraction were evaluated using full scan and tandem high resolution mass spectrometry. The dereplication revealed the presence of a major compound that could be putatively annotated as nakijiquinone A, N-carboxy-methyl-smenospongine or stachybotrin A, using the MarinLit™ database. Further investigations will be necessary to confirm the identity of the compounds responsible for the cytotoxicity and genotoxicity of the extracts of V. rugosum.