196 research outputs found
Giant multicellular magnetotactic prokaryotes in marine sediments
No full textMulticellular magnetotactic prokaryotes represent a unique group of obligately marine multicellular bacteria known for their ability to navigate along magnetic field lines thanks to ferrimagnetic nanocrystals. To date, two distinct spherical and ellipsoidal morphotypes have been described, typically ranging from 3 to 6 μm in diameter and comprising approximately 50 cells of the same species. Although widespread in highly reduced marine sediments, they are represented by solely three genera clustering into a monophyletic group within the Desulfobacterota. In this study, we report a third morphotype in reduced sediments of the Mediterranean Sea in Carry-le-Rouet, France, i.e. approximately 30 times more voluminous than any previously described form. Because their large size, we designated these multicellular bacteria as "giant" and explored their cell ultrastructure, ecological niche and physiology using magnetic enrichment and a combination of microscopy techniques and single-consortium genomics. Transmission electron microscopy and confocal microscopy images of several individual consortia revealed that they contain an average of 130 cells, each producing over 100 greigite magnetosomes arranged to optimize the overall magnetic moment. Phylogenomic analyses positioned giant multicellular magnetotactic prokaryotes, together with other morphotypes, in a previously undescribed genus and species within the Candidatus Magnetomoraceae family, named Magnetogigantoglobus mediterraneus. Although genetically divergent with a different ultrastructure, all multicellular magnetotactic prokaryotes seem to rely on sulfate reduction coupled to heterotrophy or autotrophy. We further discuss the significance of these findings in the context of the evolutionary history of multicellularity and magnetotaxis in prokaryotes
Écologie de Pseudomonas syringae dans un bassin versant (Vers un modèle de transfert)
No full textCaractériser la dissémination des bio-agresseurs est un enjeu majeur pour la gestion et la prédiction des maladies en santé des plantes. Face aux limites des approches usuelles en pathologie végétale, une nouvelle vision a été proposée abordant les paradigmes d histoire de vie des agents phytopathogènes en dehors des limites du système hôte-pathogène. Parmi ces agents phytopathogènes, les études sur P.syringae sont celles qui ont contribuées le plus à ce nouveau courant de pensée et dont on connaît le mieux l histoire de vie en relation avec ses réservoirs non hôtes . L espèce est détectée dans de nombreux compartiments du cycle de l eau, des précipitations jusqu aux rivières et eaux d irrigation, en passant par les plantes sauvages et le manteau neigeux. L ensemble de ces observations ont soulevé de nouvelles questions sur la manière dont P. syringae se dissémine au travers de ces environnements et sur les processus impactant sur la dynamique des populations à l échelle d un bassin versant. Ces recherches se sont donc intéressées à ses processus dans des précipitations jusqu aux cours d eau alpins dans l optique d acquérir des données pour la modélisation des flux de P. syringae. Elles ont mis en évidence les populations résidentes de la litière et la survie sa survie dans le sol, processus jamais identifiés à l histoire de vie de P. syringae. Elles ont également caractérisé (i) les conditions propices à son transport via les précipitations, (ii) le rôle du manteau neigeux comme réservoir et protecteur des populations des prairies alpines et (iii) ont mis en évidence la chimie de l eau comme indicateur témoin de la dynamique des populations des les rivières. Ces observations suggérant un transport de P. syringae dans le sol, nous l avons quantifiée à travers des études de terrain et des simulations en laboratoire.Enfin, l ensemble des données de ces recherches couplées à des outils SIG et des modèles météorologiques et hydrologiques ont permis de proposé un modèle sur les flux de P.syringae des habitats naturels vers les agro-systèmes.The characterization of the spread of bio-agressors spread is a major issue for themanagement of plant health and the prediction of disease emergence. Given thelimitations of conventional approaches in plant pathology, a new vision has beenproposed addressing paradigms life history of plant pathogens outside the limits of thecrop host-pathogen system. Among the plant pathogens, studies on P. syringae are thosethat have contributed the most to this new way of thought for which life history inrelation to "non host" reservoirs has been highlighted. The species is found in manycompartments of the water cycle, from precipitation to rivers and irrigation water, wildplants and snowpack. All these observations have raised new questions about how P.syringae spreads through these environments and on the processes impactingpopulation dynamics at the scale of a watershed. This research was therefore interestedin these processes with the objective to acquire data for modeling the tranfer of P.syringae through the watershed. They highlighted the resident populations of litter andtheir survival in the soil, processes never identified in association with the life history ofP. syringae. They also revealed (i) the conditions for transport via precipitations, (ii) therole of snowpack as a reservoir and protector of the populations in alpine meadows and(iii) showed that water chemistry can be used as an indicator of the populationdynamics in headwaters. These observations suggested a transport of P. syringae via thesoil that we subsequently characterized through field studies and laboratorysimulations. Finally, all data from this research combined with GIS tools andmeteorological and hydrological models have permitted us to propose a model of theflux of P. syringae of natural habitats to agricultural systems.AVIGNON-Bib. numérique (840079901) / SudocSudocFranceF
Population-genomic insights into emergence, crop-adaptation, and dissemination of Pseudomonas syringae pathogens
No full textThis is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Many bacterial pathogens are well characterized but, in some cases, relatively little is
known about the populations from which they emerged. This limits understanding of
the molecular mechanisms underlying disease. The crop pathogen Pseudomonas
syringae sensu lato has been widely isolated from the environment, including wild
plants and components of the water cycle, and causes disease in several economically
important crops. Here, we compared genome sequences of 45 P. syringae crop
pathogen outbreak strains with 69 closely related environmental isolates. Phylogenetic
reconstruction revealed that crop pathogens emerged many times independently from
environmental populations. Unexpectedly, differences in gene content between
environmental populations and outbreak strains were minimal with most virulence
genes present in both. However, a genome-wide association study identified a small
number of genes, including the type III effector genes hopQ1 and hopD1, to be
associated with crop pathogens, but not with environmental populations, suggesting
that this small group of genes may play an important role in crop disease emergence.
Intriguingly, genome-wide analysis of homologous recombination revealed that the
locus Psyr 0346, predicted to encode a protein that confers antibiotic resistance, has
been frequently exchanged among lineages and thus may contribute to pathogen
fitness. Finally, we found that isolates from diseased crops and from components of the
water cycle, collected during the same crop disease epidemic, form a single
population. This provides the strongest evidence yet that precipitation and irrigation
water are an overlooked inoculum source for disease epidemics caused by P.
syringae.Caroline L. Monteil
received support from INRA and the European Union, in the framework of the Marie-Curie FP7
COFUND People Programme, through the award of an AgreenSkills’ fellowship (under grant
agreement n° 267196). Research in Boris A. Vinatzer’s laboratory and genome sequencing was
funded by the National Science Foundation of the USA (grants IOS-1354215 and DEB-1241068).
Funding for work in the Vinatzer laboratory was also provided in part by the Virginia Agricultural
Experiment Station and the Hatch Program of the National Institute of Food and Agriculture, U.S.
Department of Agriculture. Work carried out in the Sheppard laboratory was supported by the
Medical Research Council (MRC) grant MR/L015080/1, and the Wellcome Trust grant
088786/C/09/Z. GM was supported by a NISCHR Health Research Fellowship (HF-14-13)
Features of air masses associated with the deposition of Pseudomonas syringae and Botrytis cinerea by rain and snowfall.
No full textClarifying the role of precipitation in microbial dissemination is essential for elucidating the processes involved in disease emergence and spread. The ecology of Pseudomonas syringae and its presence throughout the water cycle makes it an excellent model to address this issue. In this study, 90 samples of freshly fallen rain and snow collected from 2005-2011 in France were analyzed for microbiological composition. The conditions favorable for dissemination of P. syringae by this precipitation were investigated by (i) estimating the physical properties and backward trajectories of the air masses associated with each precipitation event and by (ii) characterizing precipitation chemistry, and genetic and phenotypic structures of populations. A parallel study with the fungus Botrytis cinerea was also performed for comparison. Results showed that (i) the relationship of P. syringae to precipitation as a dissemination vector is not the same for snowfall and rainfall, whereas it is the same for B. cinerea and (ii) the occurrence of P. syringae in precipitation can be linked to electrical conductivity and pH of water, the trajectory of the air mass associated with the precipitation and certain physical conditions of the air mass (i.e. temperature, solar radiation exposure, distance traveled), whereas these predictions are different for B. cinerea. These results are pertinent to understanding microbial survival, emission sources and atmospheric processes and how they influence microbial dissemination
Magnetosome proteins belong to universal protein families involved in many cell processes
No full textInternational audienc
Pseudomonas syringae Genomics: From Comparative Genomics of Individual Crop Pathogen Strains Toward Population Genomics
No full textSoil water flow is a source of the plant pathogen Pseudomonas syringae in subalpine headwaters.
No full textThe air-borne plant pathogenic bacterium Pseudomonas syringae is ubiquitous in headwaters, snowpack and precipitation where its populations are genetically and phenotypically diverse. Here, we assessed its population dynamics during snowmelt in headwaters of the French Alps. We revealed a continuous and significant transport of P. syringae by these waters in which the population density is correlated with water chemistry. Via in situ observations and laboratory experiments, we validated that P. syringae is effectively transported with the snow melt and rain water infiltrating through the soil of subalpine grasslands, leading to the same range of concentrations as measured in headwaters (10(2) to 10(5) CFU l(-1) ). A population structure analysis confirmed the relatedness between populations in percolated water and those above the ground (i.e. rain, leaf litter and snowpack). However, the transport study in porous media suggested that water percolation could have different efficiencies for different strains of P. syringae. Finally, leaching of soil cores incubated for up to 4 months at 8°C showed that indigenous populations of P. syringae were able to survive in subalpine soil under cold temperature. This study brings to light the underestimated role of hydrological processes involved in the long distance dissemination of P. syringae
mRNA in single skeletal muscle fibres accounts for T‐type calcium current transient expression during fetal development in mice
No full textInternational audienceCalcium channels are essential for excitation-contraction coupling and muscle development. At the end of fetal life, two types of Ca(2+) currents can be recorded in muscle cells. Whereas L-type Ca(2+) channels have been extensively studied, T-type channels have been poorly characterized in skeletal muscle. We describe here the functional and molecular properties of T-type calcium channels in developing mouse skeletal muscle. The T-type current density increased transiently during prenatal myogenesis with a maximum at embryonic day E16 followed by a drastic decrease until birth. This current showed similar electrophysiological and pharmacological properties at all examined stages. It displayed a wide window current centred at about -35 and -55 mV in 10 and 2 mM external Ca(2+), respectively. Activation and inactivation kinetics were fast (3 and 16 ms, respectively). The current was inhibited by nickel and amiloride with an IC(50) of 5.4 and 156 microM, respectively, values similar to those described for cloned T-type alpha(1H) channels. Whole muscle tissue RT-PCR analysis revealed mRNAs corresponding to alpha(1H) and alpha(1G) subunits in the fetus but not in the adult. However, single-fibre RT-PCR demonstrated that only alpha(1H) mRNA was present in prenatal fibres, suggesting that the alpha(1G) transcript present in muscle tissue must be expressed by non-skeletal muscle cells. Altogether, these results demonstrate that the alpha(1H) subunit generates functional T-type calcium channels in developing skeletal muscle fibres and suggest that these channels are involved in the early stages of muscle differentiation
The health effects of air pollution in Delhi, India
No full textThe authors report the results of a time-series study of the impact of particulate air pollution on daily mortality in Delhi. They find: a) A positive, significant relationship between particulate pollution and daily nontraumatic deaths as well as deaths from certain causes (respiratory and cardiovascular problems) and for certain age groups. b) In general, these impacts are smaller than those estimated for other countries, where on average a 100-microgram increase in total suspended particulates (TSP) leads to a 6-percent increase in nontraumatic mortality. In Delhi, such an increase in TSP is associated with a 2.3-percent increase in deaths. c) The differences in magnitudes of the effects are most likely explained by differences in distributions of age at death and cause of death, as most deaths in Delhi occur before the age of 65 and are not attributed to causes with a strong association with air pollution. d) Although air pollution seems to have less impact on mortality counts in Delhi, the number of life-years saved per death avoided is greater in Delhi than in US cities -- because the age distribution of impacts in these two places varies. In the United States particulates have the greatest influence on daily deaths among persons 65 and older. In Delhi, they have the greatest impact in the 15-to-44 age group. That means that for each death associated with air pollution, on average more life-years would be saved in Delhi than in the United States. Large differences in the magnitude of effects do call into question the validity of the"concentration-response transfer"procedure. In that procedure, concentration-response relationships found for industrial countries are applied to cities in developing countries with little or no adjustment, to estimate the effects of pollution on daily mortality.Demographics,Public Health Promotion,Montreal Protocol,Health Monitoring&Evaluation,Air Quality&Clean Air,Health Monitoring&Evaluation,Montreal Protocol,Demographics,Environmental Economics&Policies,Health Systems Development&Reform
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
- …
