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Perfil de Susceptibilidade Antimicrobiana de Bifidobacterium bifidum Bb12 e Bifidobacterium longum Bb46Bifidobacterium constitutes the most recent group of bacteria used as dietetic adjunct presenting probiotic properties such as prevention and treatment of infectious intestinal disorder. An expected characteristic for the selection of a probiotic is its antibiotic sensibility discarding the possibility of resistance transmission in the digestive ecosystem and allowing the elimination of the biotherapeutic, if necessary. In this study, the susceptibility to antibiotics of two Bifidobacterium species was tested. Bifidobacterium bifidum Bb12 and Bifidobacterium longum Bb46 have been isolated from a commercial lyophilized preparation (DVS – Christian Hansen Lab., Horsholm, Denmark). Bacteroides fragilis ATCC 25285 was used as control. The following antibiotic classes were tested: b -lactam, lincosomide, macrolide, phenolic, glycopeptide, tetracycline and aminoglycoside. The susceptibility assays of the antibiotics were performed using the standard agar dilution method (NCCLS-2000), with some modification. After inoculation and incubation during 48 hours at 37ºC, in an anaerobic chamber, the absence or presence of growth on the plates was observed. All the tests were realized in duplicate. The results showed that the both B. bifidum Bb12 and B. longum Bb46 were sensible to all of the antibiotics tested, and for all of the concentrations used, except to gentamicin. Concluding, the possibility of a transmission of antibiotic resistance from these probiotics to pathogenic bacteria can be considered to be low during the use of these biotherapeutics.
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Climate impacts on the structures of the North Pacific air-sea CO<sub>2</sub> flux variabilitySome dominant spatial and temporal structures of the North Pacific air-sea CO<sub>2</sub> fluxes in response to the Pacific Decadal Oscillation (PDO) are identified in four data products from four independent sources: an assimilated CO<sub>2</sub> flux product, two forward model solutions, and a gridded <i>p</i>CO<sub>2</sub> dataset constructed with a neural network approach. The interannual variability of CO<sub>2</sub> flux is found to be an order of magnitude weaker compared to the seasonal cycle of CO<sub>2</sub> flux in the North Pacific. A statistical approach is employed to quantify the signal-to-noise ratio in the reconstructed dataset to delineate the representativity errors. The dominant variability with a signal-to-noise ratio above one is identified and its correlations with PDO are examined. A tentative four-box structure in the North Pacific air-sea CO<sub>2</sub> flux variability linked to PDO emerges in which two positively correlated boxes are oriented in the northwest and southeast directions and contrarily, the negatively correlated boxes are oriented in the northeast and southwest directions. This pattern is verified with the CO<sub>2</sub> and <i>p</i>CO<sub>2</sub> from four products and its relations to the interannual El Niño-Southern Oscillation (ENSO) and lower-frequency PDO are separately identified. A combined EOF analysis between air-sea CO<sub>2</sub> flux and key variables representing ocean-atmosphere interactions is carried out to elicit robust oscillations in the North Pacific CO<sub>2</sub> flux in response to the PDO. The proposed spatial and temporal structures of the North Pacific CO<sub>2</sub> fluxes are insightful since they separate the secular trends of the surface ocean carbon from the interannual variability. The regional characterization of the North Pacific in terms of PDO and CO<sub>2</sub> flux variability is also instructive for determining the homogeneous oceanic domains for the Regional Carbon Cycle and Assessment Processes (RECCAP).
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Functioning of the planktonic ecosystem of the Rhone River plume (NW Mediterranean) during spring and its impact on the carbon export: a field data and 3-D modelling combined approachLow-salinity water (LSW, Salinity &lt; 37.5) lenses detached from the Rhone River plume under specific wind conditions tend to favour the biological productivity and potentially a transfer of energy to higher trophic levels on the Gulf of Lions (GoL). A field cruise conducted in May 2006 (BIOPRHOFI) followed some LSW lenses by using a lagrangian strategy. A thorough analysis of the available data set enabled to further improve our understanding of the LSW lenses' functioning and their potential influence on marine ecosystems. Through an innovative 3-D coupled hydrodynamic-biogeochemical modelling approach, a specific calibration dedicated to river plume ecosystems was then proposed and validated on field data. Exploring the role of ecosystems on the particulate organic carbon (POC) export and deposition on the shelf, a sensitivity analysis to the particulate organic matter inputs from the Rhone River was carried out from 1 April to 15 July 2006. Over such a typical end-of-spring period marked by moderate floods, the main deposition area of POC was identified alongshore between 0 and 50 m depth on the GoL, extending the Rhone prodelta to the west towards the exit of the shelf. Moreover, the main deposition area of terrestrial POC was found on the prodelta region, which confirms recent results from sediment data. The averaged daily deposition of particulate organic carbon over the whole GoL is estimated by the model between 40 and 80 mgC/m&lt;sup&gt;2&lt;/sup&gt;, which is in the range of previous secular estimations. The role of ecosystems on the POC export toward sediments or offshore areas was actually highlighted and feedbacks between ecosystems and particulate organic matters are proposed to explain paradoxical model results to the sensitivity test. In fact, the conversion of organic matter in living organisms would increase the retention of organic matter in the food web and this matter transfer along the food web could explain the minor quantity of POC of marine origin observed in the shelf sediments. Thus, the effective carbon deposition on the shelf might be strongly dependent on the zooplankton presence in the GoL. Owing to their fertilizing ability in phosphorus, the LSW lenses could then have indirectly a negative impact on the carbon deposition on the shelf by favouring the development of large phytoplankton fuelling in turn zooplankton communities. The effective carbon deposition would then be delayed out of the GoL, unless a novel transfer of matter occurs toward higher trophic levels further in the open sea through small pelagic fishes.