Heavy Metal Tolerance in Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an aerobic, non-fermentative Gram-negative bacterium widespread in the environment. S. maltophilia Sm777 exhibits innate resistance to multiple antimicrobial agents. Furthermore, this bacterium tolerates high levels (0.1 to 50 mM) of various toxic metals, such as Cd, Pb, Co, Zn, Hg, Ag, selenite, tellurite and uranyl. S. maltophilia Sm777 was able to grow in the presence of 50 mM selenite and 25 mM tellurite and to reduce them to elemental selenium (Se0) and tellurium (Te0) respectively. Transmission electron microscopy and energy dispersive X-ray analysis showed cytoplasmic nanometer-sized electron-dense Se0 granules and Te0 crystals. Moreover, this bacterium can withstand up to 2 mM CdCl2 and accumulate this metal up to 4% of its biomass. The analysis of soluble thiols in response to ten different metals showed eightfold increase of the intracellular pool of cysteine only in response to cadmium. Measurements by Cd K-edge EXAFS spectroscopy indicated the formation of Cd-S clusters in strain Sm777. Cysteine is likely to be involved in Cd tolerance and in CdS-clusters formation. Our data suggest that besides high tolerance to antibiotics by efflux mechanisms, S. maltophilia Sm777 has developed at least two different mechanisms to overcome metal toxicity, reduction of oxyanions to non-toxic elemental ions and detoxification of Cd into CdS

New fossil genus and new extant species of diatoms (Stephanodiscaceae, Bacillariophyceae)from Pleistocene sediments in the Neotropics (Guatemala,Central America): adaptation to a changing environment

Several taxa of Stephanodiscaceae were found in the upper section of Pleistocene sediments from Lake Petén-Itzá (Guatemala). A new fossil genus Cyclocostis Paillès gen. nov. and new extant species Discostellagabinii Paillès &amp; Sylvestre sp. nov. are described. Cyclocostis gen. nov. is characterized by a strongly tangentially undulated valve surface, coarse unequal striation reaching a central punctum in the valve center, an absence of central lamina and domed criba, widely open alveoli with one median recessed costa bearing marginal fultoportulae and a single rimoportula all within a ring. A single valve face fultoportula is present on the raised part of the valve opposite the rimoportula. Differences relative to similar genera and the delimitation of a new genus are discussed. Discostella gabinii sp. nov. is distinguished by circular and fl at valves, a small central area bearing 5 to &gt; 30 scattered large areolae giving a colliculate appearance, medium-sized alveoli, marginal fultoportulae on every 4–5th costa, a single rimoportula and internally smooth valve center. Differences to similar taxa in the genus Discostellaare discussed. The succession of the species of Cyclotella, Discostella and Cyclocostis gen. nov. in our record could represent eco-phenotypic responses to particular environmental stress/change.</p

Collec-Science : outil de gestion des collections scientifiques des laboratoires du CEREGE.

International audienceL’UMR CEREGE (OSU Institut Pythéas) développe des recherches concernant la paléoclimatologie et la paléocéanographie, la géodynamique et les fluides associés, la dynamique des sols, l’eau et les déchets, la morphogénèse et les risques naturels, la planétologie et la géophysique de surface, l’évolution des sols tropicaux, et les ressources en eau. A ce titre nous accumulons une multitude d’échantillons géologiques d’origines, tailles et compositions différentes (carottages marins et lacustres, roches, météorites, eaux …) qui sont répartis sur plusieurs sites, stockés à des températures différentes et dans des contenants différents (20 ans d’échantillonnage de 150 chercheurs). Une curation des stocks s'est imposée et a donné lieu à un inventaire constituant une première base de données dite "brute". Avec l'objectif d'une gestion efficace des données, constituant un enjeu crucial pour la recherche scientifique, il a été nécessaire de construire, stocker, organiser, tracer, pérenniser, rationaliser et valoriser les données en structurant l’information sous forme relationnelle. Pour ce faire, il est commode d'utiliser un système de gestion de base de données (SGBD). Le système d'information Collec-Science développé par l’INRAe de Bordeaux répond aux besoins du CEREGE en offrant non seulement une grande flexibilité des métadonnées mais aussi l'affiliation précise des échantillons et sous-échantillons. Cette application WEB, déjà déployée et utilisée dans notre laboratoire, permet une grande autonomie des chercheurs. Cet outil, parce que développé dans une logique scientifique, permet la gestion de stock dans toute la complexité des collections scientifiques. Son usage s’étendra aux autres unités de l’OSU Pythéas volontaires. De nombreux laboratoires en France (CEFE, EPOC ...) organisés en groupe de travail national l’utilisent. Dans le contexte actuel des données FAIR, nous développons cette base en intelligence avec la Cybercarothèque Nationale pour les carottages. Nous sommes en demande de supports tel que la Cybercarothèque Nationale pour les différents types d’échantillons (coraux, roches, fossiles..). Développer les relations entre bases et portails est un enjeu pour la visibilité nationale et international

Phenotypic Variation of Pseudomonas brassicacearum as a Plant Root-Colonization Strategy

International audiencePseudomonas brassicacearum was isolated as a major root-colonizing population from Arabidopsis thaliana. The strain NFM421 of P. brassicacearum undergoes phenotypic variation during A. thaliana and Brassica napus root colonization in vitro as well as in soil, resulting in different colony appearance on agar surfaces. Bacteria forming translucent colonies (phase II cells) essentially were localized at the surface of young roots and root tips, whereas wild-type cells (phase I cells) were localized at the basal part of roots. The ability of phase II cells to spread and colonize new sites on root surface correlates with over-production of flagellin as evidenced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of surface proteins and microsequencing. Moreover, phase II cells showed a higher ability to swim and to swarm on semisolid agar medium. Phase I and phase II cells of P. brassicacearum NFM421 were tagged genetically with green fluorescent protein and red fluorescent protein. Confocal scanning laser microscopy was used to localize phase II cells on secondary roots and root tips of A. thaliana, whereas phase I cells essentially were localized at the basal part of roots. These experiments were conducted in vitro and in soil. Phenotypic variation on plant roots is likely to be a colonization strategy that may explain the high colonization power of P. brassicacearum

Size Distribution of Modern Planktonic Foraminifera in the tropical Indian Ocean: Environmental Controls and Paleo-reconstruction Potentials

Présentation de congrèsPalaeoceanographic studies often rely on microfossil species abundance changes, with little consideration for traits like size that could also relate to environmental changes. We hypothesize that whole-assemblage and/or species-specific planktonic foraminiferal test size could be good predictors of environmental variables, and we test this using a tropical Indian Ocean core-top dataset. We use an automated imaging and sorting system (MiSo) and a convolutional neural network model (CNN) to identify species, analyze morphology, and quantify fragmentation using machine learning techniques. A total of 311380 images were acquired at an average of 3797 images per sample. Machine model accuracy is confirmed by comparison with human classifiers (98% accuracy achieved). Data for 32 environmental parameters are extracted from modern databases and, through Exploratory Factor Analysis and regression models, we investigate the potential of using planktonic foraminiferal size to reconstruct oceanographic parameters. The size frequency distribution of most planktonic foraminifera species is unimodal and larger species show polymodal distributions. Within our tropical dataset, we find that intraspecies size response to environmental parameters is species-specific with carbonate ion concentration, temperature, and salinity identified as primary drivers. At the assemblage level, our analyses suggest that internal biogenic processes (primary) and temperature (secondary) are key drivers of morphometric changes in planktonic foraminifera. Our assessment of the potential to utilize assemblage size in reconstructing sea surface temperature in the tropical Indian Ocean showed that the reconstructed SST of the test MD90-0963 downcore site, relatively followed the delta O18 signals from previous works for the same site

Size Distribution of Modern Planktonic Foraminifera in the tropical Indian Ocean: Environmental Controls and Paleo-reconstruction Potentials

Présentation de congrèsPalaeoceanographic studies often rely on microfossil species abundance changes, with little consideration for traits like size that could also relate to environmental changes. We hypothesize that whole-assemblage and/or species-specific planktonic foraminiferal test size could be good predictors of environmental variables, and we test this using a tropical Indian Ocean core-top dataset. We use an automated imaging and sorting system (MiSo) and a convolutional neural network model (CNN) to identify species, analyze morphology, and quantify fragmentation using machine learning techniques. A total of 311380 images were acquired at an average of 3797 images per sample. Machine model accuracy is confirmed by comparison with human classifiers (98% accuracy achieved). Data for 32 environmental parameters are extracted from modern databases and, through Exploratory Factor Analysis and regression models, we investigate the potential of using planktonic foraminiferal size to reconstruct oceanographic parameters. The size frequency distribution of most planktonic foraminifera species is unimodal and larger species show polymodal distributions. Within our tropical dataset, we find that intraspecies size response to environmental parameters is species-specific with carbonate ion concentration, temperature, and salinity identified as primary drivers. At the assemblage level, our analyses suggest that internal biogenic processes (primary) and temperature (secondary) are key drivers of morphometric changes in planktonic foraminifera. Our assessment of the potential to utilize assemblage size in reconstructing sea surface temperature in the tropical Indian Ocean showed that the reconstructed SST of the test MD90-0963 downcore site, relatively followed the delta O18 signals from previous works for the same site