Éditeur(s) : HAL CCSD Springer/Terra Scientific Publishing Company
Résumé : International audience
We report oil the discovery of magnetite nanoparticles ranging in size from 2 to 14 full in the mineralized zones of the Pena Colorada iron-ore deposit, southern Mexico. Micrometric scale magnetite was magnetically reduced and divided into distinct size ranges: 85-56 mu m, 56-30 mu m, 30-22 mu m, 22-15 mu m, 15-10 mu m, 10-7 mu m and 7-2 mu m. Nanometric-scale magnetite in the size range 2-14 nm was identified. The magnetite was characterized by X-ray diffraction, transmitted and reflected light microscope, high-resolution transmission electron microscopy (TEM), high angle annular dark field, Mossbauer spectroscopy and its magnetic properties. Crystallographic identification of nanostructures Was performed using high-resolution TEM. Characteristic changes were observed when the particles make the size transition from micro- to nanometric sizes, as follows: (1) frequency-dependent magnetic Susceptibility percentage (chi FD%) measurements Show high Values (13%) for the 2-14 nm fractions attributed to dominant fractions of superparamagnetic particles; (2) variations of chi FD% < 4.5% in fractions of 56-0.2 mu m occur in association with the presence of microparticles formed by magnetite aggregates of nanoparticles (< 15 nm) embedded in berthierine; (3) Mossbauer spectroscopy results identified a superparamagnetic fraction; (4) nanometric and 0.2-3 mu m grain size magnetite particles require a magnetic field up to 152 mT to reach saturation during the isothermal remanent magnetization experiment; (5) coercivity and remanent magnetization of the magnetite increase when the particle size decreases, probably due to parallel Coupling effects; (6) two-magnetic Susceptibility versus temperature experiments of the same 2-14 nm sample show that the reversibility during the second heating is due to the formation of new magnetite nanoparticles and growth of those already present. during the first heating process.
ISSN: 1343-8832

hal-00413053
https://hal.archives-ouvertes.fr/hal-00413053

Éditeur(s) : HAL CCSD
Résumé : The presence of biological matter (biofilms) in deep geological sites for storage of, for instance, toxic elements or groundwater in aquifers was clearly proved. That biomass triggers physical and chemical processes which greatly modify the durability and the sustainability of the sites. These processes, mainly from oxidative/reductive reactions, are poorly understood. This is mainly due to the fact that former studies were done at the macroscopic level far away from the micrometric scale where relevant processes induced by bacteria take place. Investigations at microscopic level are needed. Thus, we developed an experimental set-up based on the combined use of optical microscopy (transmission), atomic force microscopy (AFM) and electrical and electro-chemical AFM microscopy (EC_AFM) in order to get simultaneous information on topographic and electro-chemical processes. The first highly sensitive step was to use AFM with biological samples in liquid environment: wepresent here a study about AFM imaging of living, moving or self-immobilized bacteria, in their genuine physiological liquid medium and in true in vivo conditions. No external immobilization protocol, neither chemical nor mechanical was needed. For the first time, the native gliding movements of Gram negative Nostoc cyanobacteria upon the surface were studied by AFM. AFM height and mechanical stiffness data were simultaneously acquired. From these, mechanical parameters, inner turgor pressure and Young modulus, were derived for different bacterial species (Anabaenopsis circularis, Rhodococcus wratislaviensis). Our study revealed that AFM imaging is thus possible on moving living species. These results open a large window on new studies of both dynamical phenomena of practical and fundamental interests such as the formation of biofilms and dynamic properties of bacteria in real physiological conditions. The second delicate step was to combine AFM and optical measurements with electrical ones. We mounted a new experimental set-up coupling real-time (i) monitoring of optical properties as the optical density (OD) evolution related to bulk bacterial growth in liquid or as the counting of number of bacteria adhering on the surface of the sample as well and (ii) electrical and electrochemical measurements. Furthermore, these results will shortly be applied to the optimized monitoring of the in-situ activity of bacteria consuming oil pollutants, following this way, in real-time, the bioremediation of an oilcontaminated soil (ANR ECOTECH_BIOPHY program).
La présence de matière biologique (biofilms) dans les sites de stockage géologique profond, d'éléments toxiques ou encore de l'eau potable des aquifères est maintenant clairement démontrée. Cette biomasse est à l'origine de processus physiques et chimiques qui modifient considérablement la durabilité et la pérennité des sites concernés. Ces processus, principalement de type oxydo-réductif, sont encore mal compris. Ceci est principalement dû aux méthodes d'investigation, principalement macroscopiques, loin de l'échelle micrométrique caractéristique des bactéries. Seules des études, basées sur des méthodes d'investigation locale, peuvent apporter les informations requises. Ainsi, nous avons développé un dispositif expérimental basé sur l'utilisation combinée de la microscopie optique (en transmission), la microscopie à force atomique (AFM) et la microscopie AFM en mode électrique et électrochimique (EC_AFM) afin d'obtenir des informations simultanées sur la topographie de l'échantillon et sur les processus électrochimiques à l'échelle des bactéries. La première étape sensible consistait à utiliser l'AFM sur des échantillons biologiques en milieu liquide: nous présentons ici les résultats de l'imagerie AFM en milieu liquide de plusieurs types de bactéries dans leurs conditions physiologiques naturelles (conditions in vivo). Aucun protocole d'immobilisation, ni chimique ni mécanique, n'a été nécessaire; et pour la première fois, les mouvements de reptation de cyanobactéries Nostoc ont été étudiés par l'AFM. Les études AFM ont permis d'acquérir des données topographiques mais aussi mécaniques : nous avons pu ainsi mesurer le module d'Young, la pression de turgescence de différentes souches bactériennes (Anabaenopsis circularis, Rhodococcus wratislaviensis). Cette étude complète, a révélé que l'imagerie AFM est donc possible sur des espèces vivantes en mouvement. Ces résultats ouvrent une grande fenêtre sur de nouvelles études d'intérêts tels que la formation de biofilms et les propriétés dynamiques de bactéries dans des conditions physiologiques réelles. La deuxième étape délicate était de combiner l'AFM aux mesures optiques et électriques. Nous avons développé un nouveau dispositif expérimental permettant (i) le suivi de l'évolution de la croissance bactérienne par la mesure des propriétés optiques comme la densité optique DO (pour le développement bactérien en volume - milieu planctonique) , ou l'analyse de l'image du substrat par comptage du nombre de bactéries sur la surface de l'échantillon (biofilm), et (ii) les mesures électriques et électrochimiques. L'ensemble de ces résultats sera prochainement appliqué au développement de nouveaux outils de surveillance d'une biodépollution de terrain contaminé par les hydrocarbures, par le suivi in situ et en temps réel de l'activité de bactéries dépolluantes (ECOTECH_BIOPHY ANR).
https://tel.archives-ouvertes.fr/tel-01044714

tel-01044714
https://tel.archives-ouvertes.fr/tel-01044714
https://tel.archives-ouvertes.fr/tel-01044714/document
https://tel.archives-ouvertes.fr/tel-01044714/file/theseDhahri2013.pdf

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Care for malaria patients in endemic areas has been improved through the increasing use of Rapid Diagnostic Tests (RDTs). Most RDTs target the histidine-rich protein-2 antigen (PfHRP2) to detect P. falciparum, as it is abundant and shows great heat stability. However, their use in South America has been widely questioned following a recent publication that pinpoints the high prevalence of Peruvian field isolates lacking the gene encoding this protein. In the remote rural health centers of French Guiana, RDTs are the main diagnosis tools. Therefore, a study of PfHRP2 RDT performances and pfhrp2 genotyping was conducted to determine whether a replacement of the current pLDH-based kit could be considered. The performance study compared the SD Malaria Ag test P.f/Pan® kit with the current gold standard diagnosis by microscopy. The prevalence of pfhrp2 and pfhrp3 deletions were evaluated from 221 P. falciparum isolates collected between 2009 and 2011 in French Guiana. Between January 2010 and August 2011, 960 suspected cases of malaria were analyzed using microscopy and RDTs. The sensitivity of the SD Malaria Ag test P.f/Pan® for detection of P. falciparum was 96.8% (95% CI: 90.9-99.3), and 86.0% (95% CI: 78.9-91.5) for the detection of P. vivax. No isolates (95% CI: 0-4.5) lacking either exon of the pfhrp2 gene were identified among the 221 P. falciparum isolates analyzed, but 7.4% (95% CI: 2.8-15.4) lacked the exon 2 part of the pfhrp3 gene. Field isolates lacking either exon of the pfhrp2 gene are absent in this western part of South America. Despite its sensibility to detect P. vivax, the SD Malaria Ag test P.f/Pan® kit is a satisfying alternative to microscopy in remote health centers, where it is difficult to provide highly skilled microscopists and to maintain the necessary equipment.
ISSN: 1932-6203

pasteur-01109596
https://hal-riip.archives-ouvertes.fr/pasteur-01109596
https://hal-riip.archives-ouvertes.fr/pasteur-01109596/document
https://hal-riip.archives-ouvertes.fr/pasteur-01109596/file/journal.pone.0074269.pdf
DOI : 10.1371/journal.pone.0074269

Éditeur(s) : Springer
Résumé : The distribution of summer phytoplankton across the Straits of Magellan (SOM) was studied with the aims of tracing differences among the distinct subregions of the area and contributing to the knowledge of its biodiversity. Samples collected at 25 stations were observed and counted in light microscopy. Selected samples were observed with transmission electron microscopy. The main unifying feature of the phytoplankton in the SOM was the high abundance and numerical dominance of small-sized (<10 μm) eukaryotic species, among which coccoid cells of <3 μm size were predominant (56.2 ± 30.6 of the total phytoplankton abundance). They mostly belonged to the prasinophyte Pycnococcus provasolii, which was abundant (0.8–6,834 cells × 103 ml−1) at all stations with the exception of those in proximity to the Atlantic entrances, where it was not recorded. Small-sized (<3 and 3–5 μm) diatoms (Minidiscus trioculatus, Lennoxia faveolata and other undetermined centric species) attained high densities (<3,757 cells 103 ml−1) especially at stations of the Patagonian sectors, whereas microplanktonic diatoms were only found at the two entrances of the Straits. Dinoflagellates were constituted mainly by >10 μm forms in the Andean subregion and <10 μm naked species in the Patagonian subregion, contributing up to 75.9 and 41.8% of the total carbon in these two areas, respectively. In the Patagonian subregion, flagellates mainly constituted by <5 μm forms and by cryptomonads <10 μm comprised up to 53.9% of the total biomass. Several species identified in this study have never been reported in other investigations in the SOM, while others, including Pycnococcus provasolii and Lennoxia faveolata, have rarely been recorded elsewhere. Overall, the summer phytoplankton of the Straits does not resemble that of any other region of the world’s seas. Although some of the predominant species might have been overlooked elsewhere, their abundance and relative importance apparently constitute a distinctive feature of the SOM.
Polar Biology (0722-4060) (Springer), 2011 , Vol. 34 , N. 9 , P. 1269-1284

Droits : The Author(s) 2010. This article is published with open access at Springerlink.com
http://archimer.ifremer.fr/doc/00026/13722/10828.pdf
DOI:10.1007/s00300-010-0937-2
http://archimer.ifremer.fr/doc/00026/13722/

Éditeur(s) : HAL CCSD Geological Society of London
Résumé : We have applied transmission electron microscopy (TEM) analyses coupled with viscoplastic self-consistent (VPSC) numerical modelling to identify the active slip systems and to better understand the crystal preferred orientation (CPO) development of the Torridon quartz mylonite (NW Scotland). TEM analyses showed evidence of activation of 1/3〈a〉{π′}, 1/3〈a〉{z} and possible 〈a〉(c) slip systems, as well as dislocation climb and dynamic recrystallization. All the CPOs generated by VPSC models share common characteristics with the Torridon quartz mylonite, but only Models 2 and 3 reproduce the [c]-axes maxima at low angle (<20°) to the foliation pole along the YZ plane, as observed in the mylonite. In Model 2, this concentration only occurs at γ≥2.6, whereas in Model 3 this maxima occurs at lower shear strains. The models that start with a previous preferred orientation acquire very strong CPOs after small-imposed strains, followed by the rapid rotation of the fabric in relation to the new imposed finite strain axes. The combined activation of 〈a〉{π′}, 〈a〉{z} and possibly 〈a〉(c) slip systems, as demonstrated by TEM analyses, suggests that the VPSC model that best predicts CPO development in the Torridon quartz mylonite is Model 2, where the critical resolved shear stress (CRSS) of 〈a〉{π/π′} is assumed to be slightly stronger than 〈a〉(c).
Deformation Mechanisms, Rheology and Tectonics: Microstructures, Mechanics and Anisotropy

hal-00688840
https://hal.archives-ouvertes.fr/hal-00688840

Éditeur(s) : Springer
Résumé : Batch culture experiments using viral enrichment were conducted to test the response of a coastal bacterial community to autochthonous (i.e., co-existing) or allochthonous riverine viruses. The effects of viral infections on bacterial dynamics and activity were assessed by epifluorescence microscopy and thymidine incorporation, respectively, whereas the effect of viral infection on bacterial community composition was examined by polymerase chain reaction-single strand conformation polymorphism 16S ribosomal RNA fingerprinting. The percentages of high nucleic acid-containing cells, evaluated by flow cytometry, were significantly correlated (r (2) = 0.91, n = 12, p < 0.0001) to bacterial production, making this value a good predictor of active cell dynamics along the study. While confinement and temperature were the two principal experimental factors affecting bacterial community composition and dynamics, respectively, additions of freshwater viruses had significant effects on coastal bacterial communities. Thus, foreign viruses significantly reduced net bacterial population increase as compared to the enrichment treated with inactivated virus. Moreover, freshwater viruses recurrently and specifically affected bacterial community composition, as compared to addition of autochthonous viruses. In most cases, the combined treatment viruses and freshwater dissolved organic matter helped to maintain or even enhance species richness in coastal bacterial communities in agreement to the 'killing the winner' hypothesis. Thus, riverine virus input could potentially influence bacterial community composition of the coastal bay albeit with modest modification of bulk bacterial growth.
Microbial Ecology (0095-3628) (Springer), 2009-02 , Vol. 57 , N. 2 , P. 295-306

Droits : 2009 Springer
http://archimer.ifremer.fr/doc/2009/publication-6636.pdf
DOI:10.1007/s00248-008-9428-1
http://archimer.ifremer.fr/doc/00000/6636/

Éditeur(s) : EDP Sciences
Résumé : The reproductive dynamics of swordfish (Xiphias gladius) was investigated from catches of the Reunion Island-based longline swordfish fishery between 19-25 degrees S and 48-54 degrees E. Thus, 1727 swordfish (size range 75-289 cm, lower jaw-to-fork length, LJFL) were sampled on board commercial fishing vessels during the period of May 1998 to January 2001. Reproductive activity was assessed using macroscopic gonad characteristics, trends of gonadal indexes for both sexes, oocyte size-frequency distributions and microscopic investigation of oocyte development stages. Size at first maturity (L-50) for female and male swordfish was estimated in Indian Ocean for the first time. L50 was estimated at 170 cm and 120 cm (LJFL) for females and males, respectively. Spawning occurred from October to April in the vicinity of Reunion Island where sex ratio of caught populations fluctuated seasonally. The seasonal changes in sex ratio and the incidence of larger individuals at the beginning of the spawning season provide some preliminary indications of synchronized movements of swordfish between spawning grounds and neighboring regions. Our results add significantly to knowledge about the reproductive biology of swordfish in the southwestern Indian Ocean. An overview of the available information on reproductive biology and dynamics of swordfish in Indian Ocean and eastern Pacific indicated that spawning activity is localized in discrete areas, and showed that there is incomplete information on spawning grounds in this extended area.
La dynamique de la reproduction est étudiée chez des espadons (Xiphias gladius) capturés dans l'océan Indien, entre 19–25 °Sud et 48–54 °Est, par les palangriers de l'île de La Réunion. Ainsi, 1727 espadons de tailles comprises entre 75 et 289 cm (de l'extrémité de la mâchoire inférieure à la fourche caudale) ont été échantillonnés à bord de navires professionnels, de mai 1998 à janvier 2001. La reproduction est évaluée en analysant : les caractéristiques macroscopiques des gonades, l'évolution des indices gonadiques des deux sexes, les distributions de fréquence de taille des ovocytes et le développement des ovocytes au niveau microscopique. La taille à première maturité sexuelle (L50) des espadons de l'océan Indien est estimée pour la première fois ; elle atteint 170 cm pour les femelles et 120 cm pour les mâles. La saison de ponte s'étend d'octobre à avril aux abords de l'île tandis que le sexe-ratio fluctue de façon saisonnière. Les variations saisonnières du sexe-ratio et l'apparition de grands individus au début de la saison de ponte suggèrent des déplacements d'espadons entre cette zone de ponte et les régions voisines. Nos résultats apportent des informations fondamentales sur la biologie de la reproduction de l'espadon dans le sud-ouest de l'océan Indien. L'analyse de la bibliographie concernant biologie et la dynamique de la reproduction de l'espadon dans l'océan Indien et dans le Pacifique Est indique que l'activité de ponte est très localisée et que la connaissance des aires de pontes est encore incomplète dans cette région étendue.
Aquatic Living Resources (0990-7440) (EDP Sciences), 2009 , Vol. 22 , N. 1 , P. 45-58

Droits : 2009 EDP Sciences
http://archimer.ifremer.fr/doc/2009/publication-6353.pdf
DOI:10.1051/alr/2009007
http://archimer.ifremer.fr/doc/00000/6353/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We performed torsional deformation experiments on pre-hydrated fine-grained olivine aggregates using an innovative experimental assembly to investigate water weakening in mantle rocks at high shear strains. San Carlos olivine powder was cold-pressed and then hot-pressed under hydrous conditions, producing aggregates with average grain sizes of 7 or 15 μm. Deformation experiments were performed in a high-resolution gas-medium apparatus equipped with a torsional actuator, under a confining pressure of 300 MPa, a temperature of 1200 °C, and constant shear strain rates ranging from 8 × 10−5 to 1.4 × 10−4 s−1. Maximum shear stresses range from 150 to 195 MPa. These values are 30% lower relative to those determined in previous torsion experiments on dry, fined-grained dunites under similar conditions. Textures and microstructures of the starting and deformed specimens were characterized by scanning and transmission electron microscopy. All deformed aggregates exhibit a shape-preferred orientation marking a foliation and lineation, as well as a reduction in mean grain size from 15 μm down to 3-4 μm due to dynamic recrystallization. Olivine crystallographic fabrics developed rapidly (γ < 0.1), but their strength, characterized by the J-index, is low compared to naturally deformed peridotites or to polycrystalline olivine deformed at similar finite shear strains under dry conditions. The crystallographic fabrics are consistent with deformation by a dislocation accommodated creep mechanism with activation of multiple {0 k l}[1 0 0] systems, among which the (0 1 0)[1 0 0] slip system is dominant, and minor participation of the (0 1 0)[0 0 1] slip system. Transmission electron microscopy confirmed the occurrence of dislocations with [1 0 0] and [0 0 1] Burgers vectors in most grains. Analysis of unpolarized infrared spectra indicates that hydrogen concentration in the olivine lattice is below the saturation level of 18 ppm wt H2O, which is similar to those typically observed in spinel-bearing peridotite xenoliths, and also provide evidence for water-rich inter-granular material trapped in pores and grain boundaries. Seismic properties computed from the CPO observations correspond to those most commonly observed in naturally deformed mantle peridotites with fast P-wave propagation and S-wave polarization subparallel to the shear direction. These torsion experiments on fine-grained olivine polycrystals under hydrous conditions indicate that water weakening under lithospheric conditions is linked to various defects with hydrogen in the olivine structure, as well as with water-derived species in grain boundaries or pores.
ISSN: 0031-9201

hal-00745170
https://hal.archives-ouvertes.fr/hal-00745170
DOI : 10.1016/j.pepi.2012.05.001

Éditeur(s) : HAL CCSD American Geophysical Union (AGU)
Résumé : International audience
[1] The Pyrenees, north of the North Pyrenean fault, display a complex structure involving a succession of peridotite massifs, basement massifs, and mid-Cretaceous to Late Cretaceous basins located in a narrow domain, which was affected by a mid-Cretaceous, preorogenic, high-temperature, low-pressure metamorphism. The Late Cretaceous basins were interpreted either as pull-apart basins formed during transcurrent motion of Iberia relative to Eurasia or as remnants of a larger extensional basin. Recent models support that peridotite massifs result from the exhumation of the mantle during this preorogenic event. The northern boundary of the Agly basement massif shows evidence of ductile deformation of the basal formations of the Agly sedimentary cover. Macroscopic and microscopic kinematics indicators consistent with asymmetry of crystallographic fabrics suggest normal sense of shear and thus suggest detachment, at least partial, of the Mesozoic cover from its basement. Triassic to Early Cretaceous limestones are mylonitic and consistently shows a foliation, a NS- to NE-trending lineation, shear criteria suggesting top-to-the-north shearing and locally boudinage. At the microscopic scale, mylonites are characterized by a very fine grain size, frequently <10 µm. They contain larger, partially recrystallized calcite parent grains and undeformed quartz grains with calcite fringes crystallized in pressure shadows. In these mylonites, calcite systematically shows a weak but well-defined crystallographic-preferred orientations, suggesting HT dislocation creep combined to diffusion creep and possibly grain boundary sliding in the finest fraction of the mylonites. Paleotemperatures determined using Raman spectrometry suggest synkinematic temperature conditions in the range 340-390°C, in good agreement with observed microstructures and calcite CPO. The mylonitic fabric in Mesozoic limestones is folded by EW-trending Pyrenean folds north of the Agly basement massif, attesting that this fabric formed before the Pyrenean orogeny. These data consistently support preorogenic extension under medium-temperature conditions of the northern Agly massif and likely of the massif itself. Since simultaneously (~100 Ma) a mid-Cretaceous basin opened south of the basement massif, we suggest a model of preorogenic exhumation of the Agly massif in response to the regional extension associated to the rotation of Iberia. This model may explain the exhumation of the North Pyrenean massifs during a single preorogenic event that allowed the opening of extensional basins and the exhumation of the lithospheric mantle. All these structures being subsequently reworked during the Pyrenean orogeny.
ISSN: 0278-7407

hal-00852833
https://hal.archives-ouvertes.fr/hal-00852833
DOI : 10.1002/tect.20015

Éditeur(s) : Taylor & Francis Ltd
Résumé : A new benthic phototrophic dinoflagellate is described from sediments of a tropical marine cove at Martinique Island and its micromorphology is studied by means of light and electron microscopy. The cell contains small golden-brown chloroplasts and the oval nucleus is posterior. It is laterally compressed, almost circular in shape when viewed laterally. It consists of a small epitheca tilted toward the right lateral side and a larger hypotheca. In the left view, the cingulum is more anterior and the epitheca is reduced. The cingulum is displaced and left-handed. This organism is peculiar in having no apical pore and its thecal plate arrangement is 2 ' 1a 7 '' 5c 3s 5 ''' 1 ''''. The plates are smooth with small groups of pores scattered on their surface. An area with 60-80 densely arranged pores is found near the centre of the 2 ''' plate, on the left lateral side. Morphologically, these features are different from all other laterally compressed benthic genera. In addition, molecular genetic sequences of SSU and partial LSU form a distinct and well-supported clade among dinoflagellates and support the erection of a new genus. However, molecular phylogenies inferred from ribosomal genes failed to confirm any clear relationship with other benthic taxa and affinity with other laterally compressed dinoflagellates has not been demonstrated. Hence, the taxonomic affinity of Madanidinium loirii with a defined order and family is unclear at the moment.
European Journal Of Phycology (0967-0262) (Taylor & Francis Ltd), 2014-04 , Vol. 49 , N. 2 , P. 165-178

Droits : 2014 British Phycological Society
http://archimer.ifremer.fr/doc/00195/30622/29458.pdf
DOI:10.1080/09670262.2014.898797
http://archimer.ifremer.fr/doc/00195/30622/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Transmission electron microscopy observations on olivine crystals deformed at moderate (≤1273 K) temperature evidenced dislocations interactions explaining the hardening observed in the experiments, but also recovery mechanisms by the absorption or emission of point defects. Thus we investigate the possibility that, at geological strain-rates, these recovery processes allow steady-state deformation by dislocation creep at low to moderate temperatures in the lithospheric mantle. We test this hypothesis using a 2.5-D dislocation dynamics (DD) model, which combines dislocation glide and recovery by climb. This model shows that diffusion-controlled recovery processes allow for steady-state deformation by dislocation creep in the lithospheric mantle at stresses <500 MPa. For stresses of 50–200 MPa, steady-state strain-rates of 10−15 s−110−15 s−1 may be attained at temperatures as low as 900 K. Fitting of the DD model produces a flow law, which represents a lower bound for the lithospheric mantle strength, since the models describe the deformation of an olivine single crystal in an easy slip orientation. Comparison of strain-rates and Moho temperatures inferred for different geodynamic environments and the predictions of this model-based flow law implies, nevertheless, that, except in incipient rifts, most of the observed deformation may be produced by stress levels ≤200 MPa, consistent with those inferred to be produced by convection. This convergence suggests that the present models, which explicitly calculate the time-dependent dislocation dynamics, may provide a correct first order estimate of the mechanical behaviour of the lithospheric mantle, which cannot be derived directly from any existing data.
ISSN: 0012-821X

hal-01277178
https://hal.archives-ouvertes.fr/hal-01277178
https://hal.archives-ouvertes.fr/hal-01277178/document
https://hal.archives-ouvertes.fr/hal-01277178/file/Boioli.pdf
DOI : 10.1016/j.epsl.2015.10.012

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
This study describes the structure of the digestive gland of Strombus gigas in individuals from Guadeloupe and discusses the function of its cell types and their relationship with intracellular Apicomplexa-like parasites. Three cellular types were found in the epithelium of the blind-ending tubules of the digestive gland according to histological and transmission electron microscopy (TEM) observations; these were: digestive cells, pyramidal crypt cells and vacuolated cells. Columnar digestive cells were characterized by large Alcian blue-positive granules, which have not been previously described in digestive cells of other caenogastropods. Such granules contain large quantities of proteoglycans that are exported to the stomach through the physiological destruction of the digestive cells, which undergo a holocrine secretion. Their cytoplasm appears vacuolar due to lipid extraction by solvents used for tissue preparation. Vacuolated cells also appear to be lipid-storage cells. Small triangular-shaped crypt cells, on the other hand, appear to be metabolically active as suggested by a strong positive in situ hybridization of eukaryotic ribosomes, which was confirmed by their large content of ribosomes and rough endoplasmic reticulum compared to the other cell types. These observations suggest that crypt cells may be immature cells that are involved in the replacement of eliminated digestive cells. However, their spherocrystal inclusions indicate that they may be excretory cells or calcium cells. Large brown inclusions were frequently observed in vacuolated cells; these were identified as parasitic protozoans and were present in the digestive gland of all sampled specimens. These protozoans have previously been described from a queen conch population in the San Andres Archipelago (Colombia). Several life cycle stages of the parasite were identified by scanning electron microscopy and TEM; trophozoites were characterized by their conoid-like structure, sporocysts by their thick walls, and gamonts by their thin walls. These observations suggest that this parasite completes its entire life cycle within the same host and type of tissue. Although previous investigations place this parasite within the Apicomplexa group, further investigations are necessary in order to confirm the identification of the parasite.
ISSN: 0260-1230

hal-00755287
https://hal.univ-antilles.fr/hal-00755287
DOI : 10.1093/mollus/eyn041

Éditeur(s) : HAL CCSD
Résumé : Staphylococcus aureus is an opportunistic pathogen of humans and warm-blooded animals. It is foundin healthy carriage and can cause a wide range of infections in its hosts. The epithelial surface is theprincipal site of staphylococcal infection. The pathogens have evolved sophisticated mechanisms tohijack the main function of the host cells, thus promoting their invasion and colonization. Amongstthese effects are, alteration of host cell apoptosis, promotion of cell proliferation or conversely,inhibition of cell growth. Using human cervix cancer HeLa and mammary gland bovine MAC-Tepithelial cells, we studied the cytopathic effect of S. aureus and its ability to affect host cell cycle.Using microscopic examination, we found that S. aureus induced the cytopathic effect resulting in theenlargement of the host cells 72 hours post infection. Our experiments showed that the proliferationrate of the epithelial cells was slowed down in S. aureus-infected culture. Three different S. aureusstrains from human and animal origins were used and showed similar effect on both human and bovinecells. Microscopic analysis of DAPI-stained cells revealed huge decrease of mitotic indexes in infectedHeLa and Mac-T cells, synchronized by Double Thymidine Block. Using flow cytometry analysis, wefound that S. aureus induces G2/M phase delay in synchronous HeLa cells. By Western blot analysis,we showed that the G2/M phase delay was associated with accumulation of inactive phosphorylatedcyclin-dependent kinase Cdk1/cdc2, a key inducer of mitosis entry, and dephosphorylation of corehistone H3, an important component of the epigenetic landscape.These results suggest that the delay in G2/M phase transition of the infected epithelial cells may beone of the mechanisms employed by S. aureus to survive and to propagate inside the host. A fullcomprehension of the mechanisms associated to S. aureus-host cell interactions will undoubtedly helpto discover novel targets to treat staphylococcal infections.
EMBO
Villars sur Ollon, Switzerland

hal-01454214
https://hal.archives-ouvertes.fr/hal-01454214
PRODINRA : 171657

Éditeur(s) : Blackwell science
Résumé : A study was conducted to evaluate variations of digestive enzyme activities in Litopenaeus vannamei (Boone) reared in commercial ponds under semi-intensive conditions. Shrimp were collected at each body weight increase of 2 g. As the shrimp grew (2-12 g), significant increases in the activities of lipase and chymotrypsin were observed. The total protease activity decreased from 6 g onwards. Trypsin activity showed a peak at 6 g and amylase activity increased two-fold after 2 g. Additionally, the stomach contents were analysed microscopically for shrimp between 2 and 10 g. Plant matter contributed above 30% of the total stomach content in 6-, 8- and 10-g shrimp. Detritus represented 58% and 62% of the total stomach content in 2- and 4-g shrimp, respectively, decreasing to 33-43% at greater shrimp weights. Artificial feed showed a maximum contribution of 20% in 6-g shrimp. The present results show changes in the enzyme activity after the shrimp reach 6 g in body weight, evidenced by a decrease in total protease and an increase in lipase and amylase activities. The amylase/protease ratio was 2.6 in 2-g shrimp and increased steadily to 9.6 in 12-g shrimp. These findings suggest an adaptation of the enzymatic activity to diets with lower protein content as body weight increases, and may be related to the variation of the different items found in the stomach.
Aquaculture Research (1355-557X) (Blackwell science), 2003-12 , Vol. 34 , N. 15 , P. 1403-1411

Droits : Blackwell Publishing, Inc.
http://archimer.ifremer.fr/doc/2003/publication-902.pdf
DOI:10.1111/j.1365-2109.2003.00959.x
http://archimer.ifremer.fr/doc/00000/902/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Second harmonic generation (SHG) microscopy is a powerful tool for studying submicron architecture of muscles tissues. Using this technique, we show that the canonical single frequency sarcomeric SHG intensity pattern (SHG-IP) of premetamorphic xenopus tadpole tail muscles is converted to double frequency (2f) sarcomeric SHG-IP in metamorphic climax stages due to massive physiological muscle proteolysis. This conversion was found to rise from 7% in premetamorphic muscles to about 97% in fragmented muscular apoptotic bodies. Moreover a 66% conversion was also found in non-fragmented metamorphic tail muscles. Also, a strong correlation between predominant 2f sarcomeric SHG-IPs and myofibrillar misalignment is established with electron microscopy. Experimental and theoretical results demonstrate the higher sensitivity and the supra resolution power of SHG microscopy over TPEF to reveal 3D myofibrillar misalignment. From this study, we suggest that 2f sarcomeric SHG-IP could be used as signature of triad defect and disruption of excitation–contraction coupling. As the mechanism of muscle proteolysis is similar to that found in mdx mouse muscles, we further suggest that xenopus tadpole tail resorption at climax stages could be used as an alternative or complementary model of Duchene muscular dystrophy.
ISSN: 1047-8477

hal-01134174
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01134174
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01134174/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01134174/file/Recher%20et%20al_JSB-2015_hal.pdf
DOI : 10.1016/j.jsb.2015.03.003

Éditeur(s) : HAL CCSD Optical Society of America
Résumé : International audience
We present a theoretical simulation of the sarcomeric SHG intensity pattern (SHG-IP) that takes into account myofibrillar misalignment that is experimentally observed in SHG images of proteolysed muscles. The model predicts that myofibrillar displacement results in the conversion from one peak (1P) to two peaks (2P) sarcomeric SHG-IP in agreement with experimental results. This study suggests that sarcomeric SHG-IP is a powerful tool for mapping spatial myofibrillar displacement and its related excitation-contraction disruption that could occur during muscle physiological adaptation and disease.
ISSN: 1094-4087

hal-00820260
https://hal.archives-ouvertes.fr/hal-00820260
https://hal.archives-ouvertes.fr/hal-00820260/document
https://hal.archives-ouvertes.fr/hal-00820260/file/Studysur the_effect-accepted.pdf
DOI : 10.1364/OE.21.011404

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Polarization dependence second harmonic generation (P-SHG) microscopy is gaining increase popularity for in situ quantification of fibrillar protein architectures. In this report, we combine P-SHG microscopy, new linear least square (LLS) fitting and modeling to determine and convert the complex second-order non-linear optical anisotropy parameter ρ of several collagen rich tissues into a simple geometric organization of collagen fibrils. Modeling integrates a priori knowledge of polyhelical organization of collagen molecule polymers forming fibrils and bundles of fibrils as well as Poisson photonic shot noise of the detection system. The results, which accurately predict the known sub-microscopic hierarchical organization of collagen fibrils in several tissues, suggest that they can be subdivided into three classes according to their microscopic and macroscopic hierarchical organization of collagen fibrils. They also show, for the first time to our knowledge, intrahepatic spatial discrimination between genuine fibrotic and non-fibrotic vessels. CCl 4-treated livers are characterized by an increase in the percentage of fibrotic vessels and their remodeling involves peri-portal compaction and alignment of collagen fibrils that should contribute to portal hypertension. This integrated P-SHG image analysis method is a powerful tool that should open new avenue for the determination of pathophysiological and chemo-mechanical cues impacting collagen fibrils organization.
ISSN: 2045-2322

hal-01592192
https://hal.archives-ouvertes.fr/hal-01592192
https://hal.archives-ouvertes.fr/hal-01592192/document
https://hal.archives-ouvertes.fr/hal-01592192/file/s41598-017-12398-0.pdf
DOI : 10.1038/s41598-017-12398-0

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Microalgae in the division Haptophyta play key roles in the marine ecosystem and in global biogeochemical processes. Despite their ecological importance, knowledge on seasonal dynamics, community composition and abundance at the species level is limited due to their small cell size and few morphological features visible under the light microscope. Here, we present unique data on haptophyte seasonal diversity and dynamics from two annual cycles, with the taxonomic resolution and sampling depth obtained with high-throughput sequencing. From outer Oslofjorden, S Norway, nano- and picoplanktonic samples were collected monthly for 2years, and the haptophytes targeted by amplification of RNA/cDNA with Haptophyta-specific 18S rDNA V4 primers. We obtained 156 operational taxonomic units (OTUs), from c. 400.000 454 pyrosequencing reads, after rigorous bioinformatic filtering and clustering at 99.5%. Most OTUs represented uncultured and/or not yet 18S rDNA-sequenced species. Haptophyte OTU richness and community composition exhibited high temporal variation and significant yearly periodicity. Richness was highest in September-October (autumn) and lowest in April-May (spring). Some taxa were detected all year, such as Chrysochromulina simplex, Emiliania huxleyi and Phaeocystis cordata, whereas most calcifying coccolithophores only appeared from summer to early winter. We also revealed the seasonal dynamics of OTUs representing putative novel classes (clades HAP-3-5) or orders (clades D, E, F). Season, light and temperature accounted for 29% of the variation in OTU composition. Residual variation may be related to biotic factors, such as competition and viral infection. This study provides new, in-depth knowledge on seasonal diversity and dynamics of haptophytes in North Atlantic coastal waters. See also the Perspective by Massana
ISSN: 0962-1083

hal-01545321
https://hal.archives-ouvertes.fr/hal-01545321
DOI : 10.1111/mec.13160

Résumé : Les mattes de procaryotes constituent une niche écologique diversifiée. peu étudié!<..en mangrove et jamais décrjte dans les Antilles. L'objectif de cette thèse est de décrire les procaryotes filamenteux reposant sur le sédiment marin et de caractériser les interactions entre la matte, milieu et entre les différents micro-organismes. Nous avons d'abord caractérisé les micro-organismes majoritaires de la matte par le séquençage de l'ADNr 16S et des hybridations moléculaires (FISH). Il a ainsi été possible de décrire deux nouvelles espèces de Beggiatoaceae dont la structure a été étudiée par microscopie électronique. De plus, afin de caractériser l'environnement chimique de ces bactéries, des capteurs potentiométriques ont été utilisés. Ils ont permis de démontrer que les Beggiaotaceae oxydaient les sulfures en prélevant l'oxygène du milieu, tandis que des analyses de microscopie couplées à de l'EDX ont mis en évidence des réserves de soufre intracellulaires dans ces bactéries. Le séquençage de l'ADNr 16S des cyanobactéries filamenteuses a mis en évidence quatre nouvelles espèces de l'ord~e des Oscillatoriales. Deux d'entre elles, du genre Planktothricoides ont révélé une toxicité positive sur les Artemia sp:, les deux autres ont été identifiées comme proches d'Oscillatoria spongeliae, une espèce symbiotique d'éponge, bien que les coupes uItrafines d'une de ces souches aient montré une morphologie interne proche des Tychonema. L'analyse des données a permis d'étoffer les connaissances sur les communautés microbiennes de mangrove et constitue une base intéressante de travail sur la contribution des micro-organismes au fonctionnement de l'écosystème mangrove dans son ensemble
Procaryotic mats are ecological niches, occuring in many ecosystems. Those structures are little studied in marine mangrove sediment and have never been described in West Indies. The purpose ofthis thesis is to characterize the interactions between the mat and the environment, and between the different filamentous micro-organisms living into the mat. In a first place, we characterized the mainly micro-organisrns of the mat by sequencing 16S rDNA. We confirmed these sequences by molecular hybridization (FISH) with specific probes designed from sequences obtained. Thus, it was possible to describe two new Beggiatoaceae strains, whose structure has been studied by electronic microscopy. Furthemore, we used potentiometric captors in situ and in laboratory, by creating a mesocosm, in order to define the chemical environment where involved these bacteria. These experiences proved that the Beggiatoaceae of the mat oxidized the sulfur taking the oxygen from the medium, while the microscopic analysis coupled with EDX showed intracellular sulfur granules into the bacteria. The study of the filamentous cyanobacteria of the mat highlighted four new cyanobacteria strains, all studied by electronic rmcroscopy. Two of them belongs to Planktothrlcoides genus and showed positive toxicity on Artemia salina. The others species are close to Oscillatorla spongeliae, a sponge symbiont, nevertheless, one ofthem showed an intemal morphology close to Tychonema. The analysis of the different results adduces sorne knowledge about mangrove microbial communities. Furthermore, this study can be used as an interesting base to study the micro-organisms contribution in functioning mangrove ecosystem

http://www.theses.fr/2013AGUY0614/document

Éditeur(s) : HAL CCSD American Physical Society
Résumé : We study the equilibrium properties of a liquid phase condensed at the nanoscale between the surfaces of a sharp crack in fused silica in a moist controlled atmosphere. The extension of the condensed phase along the fracture is measured by in situ atomic force microscopy phase imaging and it is shown to be determined by a critical distance between the opposite crack surfaces, which is an increasing function of humidity. The present technique is very promising for measuring the properties of confined liquids at the nanoscale as well as for modeling the physics and chemistry of slow crack propagation in glasses.
ISSN: 0031-9007

hal-00411946
https://hal.archives-ouvertes.fr/hal-00411946
DOI : 10.1103/PhysRevLett.100.165505