Functional Microbial Features Driving Community Assembly During Seed Germination and Emergence

Microbial interactions occurring on and around seeds are especially important for plant fitness since seed-borne microorganisms are the initial source of inoculum for the plant microbiota. In this study, we analyze structural and functional changes occurring within the plant microbiota at these early stages of the plant cycle, namely germination and emergence. To this purpose, we performed shotgun DNA sequencing of microbial assemblages associated to seeds, germinating seeds and seedlings of two plant species: bean and radish. We observed an enrichment of and during emergence and a set of functional traits linked to copiotrophy that could be responsible for this selection as a result of an increase of nutrient availability after germination. Representative bacterial isolates of taxa that are selected in seedlings showed indeed faster bacterial growth rate in comparison to seed-associated bacteria isolates. Finally, binning of metagenomics contigs results in the reconstruction of population genomes of the major bacterial taxa associated to the samples. Together, our results demonstrate that, although seed microbiota varied across plant species, nutrient availability during germination elicits changes of the composition of microbial communities by potentially selecting microbial groups with functional traits linked to copiotrophy. The data presented here represents the first attempts to empirically assess changes in the microbial community during plant emergence and moves us toward a more holistic understanding of the plant microbiome

Differences in resource use lead to coexistence of seed-transmitted microbial populations

Seeds are involved in the vertical transmission of microorganisms in plants and act as reservoirs for the plant microbiome. They could serve as carriers of pathogens, making the study of microbial interactions on seeds important in the emergence of plant diseases. We studied the influence of biological disturbances caused by seed transmission of two phytopathogenic agents, Alternaria brassicicola Abra43 (Abra43) and Xanthomonas campestris pv. campestris 8004 (Xcc8004), on the structure and function of radish seed microbial assemblages, as well as the nutritional overlap between Xcc8004 and the seed microbiome, to find seed microbial residents capable of outcompeting this pathogen. According to taxonomic and functional inference performed on metagenomics reads, no shift in structure and function of the seed microbiome was observed following Abra43 and Xcc8004 transmission. This lack of impact derives from a limited overlap in nutritional resources between Xcc8004 and the major bacterial populations of radish seeds. However, two native seed-associated bacterial strains belonging to Stenotrophomonas rhizophila displayed a high overlap with Xcc8004 regarding the use of resources; they might therefore limit its transmission. The strategy we used may serve as a foundation for the selection of seed indigenous bacterial strains that could limit seed transmission of pathogens

Respuesta biológica, nutricional y hematoinmune en juveniles Cherax quadricarinatus (Decapoda: Parastacidae) alimentados con mezcla probiótica

Objetivo: Evaluar indicadores biológicos, nutricionales y hematoinmunes en juveniles Cherax quadricarinatus que fueron cultivados y alimentados con una mezcla de probióticos. Materiales y métodos: Un diseño completamente aleatorizado (DCA) con seis tratamientos: 0 (control), 1×102 µL, 2×102 µL, 3×102 µL, 4×102 µL y 5×102 µL de mezcla de probióticos (Bacterol Shrimp Forte), con tres repeticiones cada una; se utilizaron 18 tanques experimentales de diametro 1.7 m y área de 2.26 m2, con una densidad de 20 juveniles (0.95±0.10 g y 7.78±0.77mm) por tanque durante 60 días. Se midieron los parámetros biológicos (peso, longitud, aumento de peso, aumento de peso, tasa de crecimiento específico, aumento de longitud, aumento de longitud y supervivencia), nutricionales (conversión alimenticia, eficiencia alimenticia y eficiencia proteica) y hematoinmune (total de hemocitos, hemocitos diferenciales, tasa fagocítica, superóxido dismutasa y estrés hipóxico). Resultados: Para los indicadores biológicos, los mejores resultados (p<0.05) se obtuvieron al utilizar 4×102 µL del probiótico (peso final: 9.11 g; longitud final: 68.95 mm; tasa de crecimiento específico: 3.74). En cuanto a los parámetros nutricionales, los mejores resultados se obtuvieron con 3×102 µL (conversion alimenticia: 1.09, eficiencia alimenticia: 0.91 y eficiencia proteica: 2.61); aunque no hubo diferencias entre 3×102 y 4×102 µL. Para la respuesta hematoinmune, hubo diferencias (p <  0.05) para todos los indicadores en estudio, con un mejor desempeño para 4×102 µL de la mezcla de probióticos. Conclusiones: La mezcla de probióticos induce la respuesta hematoinmune, biológica y nutricional con la mejor respuesta para concentraciones de 3×102 µL y 4×102 µL

Nanostructured thin films obtained from Fischer aminocarbene complexes

The synthesis of four amphiphilic organometallic complexes with the general formula RC = M(CO)5NH(CH2)15CH3, where R is a ferrocenyl 2(a-b) or a phenyl 4(a-b) group as a donor moiety and a Fischer carbene of chromium (0) or tungsten (0) as an acceptor group, are reported. These four push-pull systems formed Langmuir (L) monolayers at the air-water interface, which were characterized by isotherms of surface pressure versus molecular area and compression/expansion cycles (hysteresis curves); Brewster angle microscopic images were also obtained. By using the Langmuir-Blodgett (LB) method, molecular monolayers were transferred onto glass substrates forming Z-type multilayers. LB films were characterized through ultraviolet-visible spectroscopy, atomic force microscopy and X-ray diffraction techniques. Results indicated that films obtained from 2b complex [(Ferrocenyl)(hexadecylamine)methylidene] pentacarbonyl tungsten (0) are the most stable and homogeneous; due to their properties, these materials may be incorporated into organic electronic devices

Charge separation relative to the reaction plane in Pb-Pb collisions at sNN=2.76\sqrt{s_{\rm NN}}= 2.76 TeV

Measurements of charge dependent azimuthal correlations with the ALICE detector at the LHC are reported for Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV. Two- and three-particle charge-dependent azimuthal correlations in the pseudo-rapidity range $|\eta| < 0.8$ are presented as a function of the collision centrality, particle separation in pseudo-rapidity, and transverse momentum. A clear signal compatible with a charge-dependent separation relative to the reaction plane is observed, which shows little or no collision energy dependence when compared to measurements at RHIC energies. This provides a new insight for understanding the nature of the charge dependent azimuthal correlations observed at RHIC and LHC energies.Comment: 12 pages, 3 captioned figures, authors from page 2 to 6, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/286

A note on comonotonicity and positivity of the control components of decoupled quadratic FBSDE

In this small note we are concerned with the solution of Forward-Backward Stochastic Differential Equations (FBSDE) with drivers that grow quadratically in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem is a comparison result that allows comparing componentwise the signs of the control processes of two different qgFBSDE. As a byproduct one obtains conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio