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Roue M.,Laboratoire Molecules Of Communication Et Adaptation Des Microorganismes | Domart-Coulon I.,Laboratoire Biologie des Organismes et des Ecosystemes Aquatiques | Ereskovsky A.,Saint Petersbourg State University | Djediat C.,Service de Microscopie Electronique | And 2 more authors.
Journal of Natural Products | Year: 2010

Chemical investigation of the Mediterranean calcareous sponge Clathrina clathrus led to the isolation of large amounts of a new 2-aminoimidazole alkaloid, named clathridimine (1), along with the known clathridine (2) and its zinc complex (3). The structure of the new metabolite was assigned by detailed spectroscopic analysis. Clathridimine (1) displayed selective anti-Escherichia coli and anti-Candida albicans activities. Clathridine (2) showed only anti-Candida albicans activity, and its zinc complex (3) exhibited selective anti-Staphylococcus aureus activity. The isolation of analogues of 2-amino-imidazole derivatives from several Leucetta species from various sites in the Pacific Ocean and the Red Sea raises the question of their biosynthetic origin. Microscopic studies revealed abundant extracellular bacteria located in the mesohyl of the sponge, with two predominant morphotypes including spiral bacteria and long, narrow bacilli. Chemical analysis with HPLC/UV/ELSD profiles of sponge cells separated from bacteria by differential centrifugation and trypsinization of the sponge cell surface revealed that clathridine (2) was localized in the sponge cells. © 2010 The American Chemical Society and American Society of Pharmacognosy.


Park Y.-H.,French Natural History Museum | Durand I.,French Natural History Museum | Kestenare E.,University Paul Sabatier | Rougier G.,Center Doceanologie Of Marseille | And 4 more authors.
Journal of Geophysical Research C: Oceans | Year: 2014

The circulation of iron-rich shelf waters around the Kerguelen Islands plays a crucial role for a climatically important, annually recurrent phytoplankton spring bloom over the sluggish shelf region and its downstream plume area along the Antarctic circumpolar flow. However, there is a long-standing confusion about the Polar Front (PF) in the Kerguelen region due to diverse suggestions in the literature for its geographical location with an extreme difference over 10 of latitude. Based on abundant historical hydrographic data, the in situ hydrographic and current measurements during the 2011 KEOPS2 cruise, satellite chlorophyll images, and altimetry-derived surface velocity fields, we determine and validate an up-to-date location of the PF around the Kerguelen Islands. Artificial Lagrangian particle trajectories computed from altimetric velocity time series are analyzed for the possible pathways and sources of different surface/subsurface waters advected into the chlorophyll bloom area east off the islands studied during the KEOPS2 cruise. The PF location determined as the northernmost boundary of the Winter Water colder than 2°C, which is also associated with a band of strong currents, appears to be primarily controlled by topography. The PF rounds the Kerguelen Islands from the south to deflect northward along the eastern escarpment up to the northeastern corner of the Kerguelen Plateau before making its southward retroflection. It is shown that the major surface/subsurface waters found within the deep basin east of the Kerguelen Islands originate from the shelf around the Heard Island, rather than from the shallow shelf north of the Kerguelen Islands. © 2014. The Authors.


Rontani J.-F.,Center Doceanologie Of Marseille | Wakeham S.G.,Skidaway Institute of Oceanography | Prahl F.G.,Oregon State University | Vaultier F.,Center Doceanologie Of Marseille | Volkman J.K.,CSIRO
Organic Geochemistry | Year: 2011

The U37K' index is widely used to infer paleo-sea surface temperatures from the relative abundances of sedimentary 37:3 and 37:2 methyl alkenones. However, the measurements can be difficult and error prone when the alkenones are present in only trace amount, when one is much more abundant than the other, or when co-eluting compounds are present. Silylated alkenols can be analyzed by way of gas chromatography-electron ionization mass spectrometry (GC-EIMS) with much greater sensitivity and specificity than the parent alkenones and near-baseline resolution can be obtained without the use of very long chromatographic columns and/or slow temperature programs. We show, using particulate matter from the Black Sea and the DYFAMED site in the Ligurian Sea, and surface sediments from the Black Sea and SE Alaska, that conversion of C 37 alkenones to alkenols using NaBH 4 reduction and subsequent derivatization to TMSi ethers allows U37K' values to be reliably calculated without time consuming purification steps, using the relative abundances of the diagnostic m/z 117 ion. The response factor for m/z 117 varies for 37:3 and 37:2 alkenols, so a specific correction is required. The reduction method is easy to use, highly sensitive and widely applicable. Ethyl alkenols give a characteristic ion at m/z 131 and, if NaBD 4 is used, the ions at m/z 117 and 131 shift to m/z 118 and 132, providing further confirmation of the structures. © 2011 Elsevier Ltd.


Rontani J.-F.,Center Doceanologie Of Marseille | Zabeti N.,Center Doceanologie Of Marseille | Wakehamb S.G.,Skidaway Institute of Oceanography | Wakehamb S.G.,University of Washington
Limnology and Oceanography | Year: 2011

The behavior of organic matter (OM) in suspended and sinking particles in the equatorial Pacific Ocean was monitored by measuring lipid degradation products that are specific for biodegradation, photooxidation, and autoxidation. Photodegradation and autoxidation were significant for lipids associated with both suspended and sinking particles. Abiotically degraded terrestrial material strongly contributed to suspended particles and to sinking material in the deep ocean, probably as the result of incorporation of terrestrial particles into sinking aggregates. Analyses of degradation products of 24-methylcholesta-5,22- dien-3βb-ol, 24-ethylcholest-5-en-3β-ol, and cholest-5-en-3β-ol gave diagnostic information concerning the differential behavior of phytoplanktonic, terrestrial, and zooplanktonic OM, respectively. Planktonic lipids were more susceptible to biodegradation than terrestrial lipids and biodegradation was more intense in sinking particulate organic matter (POM) than suspended POM, which we attribute to efficient transfer of singlet oxygen from suspended and senescent phytoplankton cells to associated bacteria and subsequent inhibition of heterotrophic degradation. There is a direct link between the photooxidation state of lipids of senescent phytoplankton cells in suspended particles and the apparent resistance of lipids toward biotic degradation. Terrigenous vascular plant OM, which is strongly autoxidized on land or in the atmosphere as it is transported to the remote ocean, is only weakly biodegraded during sedimentation in this open ocean setting. A significant increase in alkenone-based UK' 37 values (+0.07 equivalent to an inferred temperature change of +2°C) was observed in sinking particles with depth and the detection of epoxyalkenones further confirming the potential detrimental effect of aerobic bacterial degradation processes on the UK' 37 paleotemperature proxy. © 2011, by the American Society of Limnology and Oceanography, Inc.


Gannier A.,British Petroleum | Fuchs S.,British Petroleum | Quebre P.,Center Doceanologie Of Marseille | Oswald J.N.,Hawaii Institute of Marine Biology
Applied Acoustics | Year: 2010

Whistles from five delphinid species in the western Mediterranean Sea (Stenella coeruleoalba, Grampus griseus, Delphinus delphis, Tursiops truncatus, Globicephala melas) were taken from CREC sound archives. FFT contours (window size 512, Hanning, sampling frequency 44.1 kHz) were extracted with custom developed Matlab software: 277 samples of striped dolphins (Sc), 158 whistles of Risso's dolphins (Gg), 120 of common dolphins (Dd), 76 of bottlenose dolphins (Tt), and 66 of pilot whales (Gm) were selected. Seafox software extracted 15 variables from the digitized contours, including: duration, initial, final, maximal and minimal frequency slopes, frequency range, number of frequency extrema, beginning, ending, maximal and minimal frequencies, presence of harmonics. Four of five species were significantly different (Mann-Whitney test) for average durations (respectively 0.73, 0.65, 0.47 and 0.89 s for Sc, Gg, Dd, Gm) while the average duration of bottlenose dolphins was 0.71 s. Frequency ranges (respectively 7.3, 6.3, 4.6, 3.2 and 6.3 kHz) were significantly different for all species pairs, with the exception of bottlenose and Risso's dolphins. From a global point of view, pilot whale calls were the most distinct, with 43 significant pair-wise tests out of a total of 52, followed by the common dolphins. Risso's dolphins were closest to other species whistles. A CART classification method achieved a global classification rate of 62.9%. © 2010 Elsevier Ltd. All rights reserved.


Prahl F.G.,Oregon State University | Rontani J.-F.,Center Doceanologie Of Marseille | Zabeti N.,Center Doceanologie Of Marseille | Walinsky S.E.,Oregon State University | Sparrow M.A.,Oregon State University
Geochimica et Cosmochimica Acta | Year: 2010

Twenty-seven multicores, collected in late summer 2004 from coastal and inland marine sites throughout SE Alaska (∼55 to 61°N), were analyzed for C37 to C39 alkenones of specific haptophyte origin. This biomarker signal, detected in core-top sediments from 20 of the sites, was quantitatively most significant in organic carbon and biogenic silica-rich sediments deposited south of Icy Strait (∼58°N), along the outer coastline of Baranof and Prince of Wales islands. U37 K′-based water temperature estimates derived using a standard calibration equation (U37 K′ = 0.034T + 0.039) were uniform throughout the study area, averaging 11.9 ± 1.0 °C, a value ∼4 °C warmer than mean annual SST (maSST) for the region. Epoxides, indicative of selective alkenone degradation by an aerobic bacterial process, were also detected and quantified in all sediments containing alkenones. Semi-quantitative accounting of the impact that compound-selective degradation can impose on alkenone unsaturation patterns indicates the standard U37 K′-based temperature estimates could be too warm by a variable amount (0.7-2.4 °C) depending upon the site, with an overall average of ∼1.4 °C. Even after adjustment for this potential diagenetic 'warming' effect, estimates still best match summer and not maSST in this subarctic region. Re-examination of alkenone signatures preserved in sediment from the North Atlantic and on the continental margin located south of ∼45°S along the Chilean coast indicates the apparent summer signal in U37 K′-derived SST estimates is not unique to SE Alaskan sediments but rather a common finding when alkenone thermometry is applied to sediments from high latitude environments. Examination of model residuals from analysis of surface sediment samples collected at lower latitude settings along the west coast of the Americas also identifies other sites where significant biogeographic patterns seem apparent and viable oceanographic explanations can be offered. © 2009 Elsevier Ltd. All rights reserved.


Torreton J.-P.,Montpellier University | Rochelle-Newall E.,Montpellier University | Pringault O.,Montpellier University | Jacquet S.,Montpellier University | And 2 more authors.
Marine Pollution Bulletin | Year: 2010

We assessed the temporal variability of nutrients, phytoplankton and bacterioplankton at two sites of different trophic status in New Caledonia's South-West lagoon, a tropical coastal ecosystem. During stable meteorological conditions, Chl.a, bacterial production and nutrient concentrations experience weak but consistent daily variation. Short-term (1-2. week interval) fluctuations of planktonic variables are in the same range as annual variations at both sites. A part of these short term variations is linked to local meteorological events (wind in the main channel, precipitation at the coastal station). Although annual variations are weak compared to short term variations, phytoplankton and bacterioplankton production show consistent temporal patterns, with maxima in December-January and April-May and minima in August. Annual bacterial production represents 21% and 34% of particulate primary production at the oligotrophic and mesotrophic sites, respectively. Mineral nutrient availability indicates that nitrogen is probably the primary limiting factor of phytoplankton throughout the year. © 2010 Elsevier Ltd.


Rontani J.-F.,Center Doceanologie Of Marseille | Belt S.T.,University of Plymouth | Vaultier F.,Center Doceanologie Of Marseille | Brown T.A.,University of Plymouth
Organic Geochemistry | Year: 2011

Visible light induced, type II (i.e. involving singlet oxygen, 1O2) photosensitized oxidation of mono-, di-, tri- and tetraunsaturated C25 highly branched (HBI) alkenes in solution was investigated. The photodegradation rate was shown to be dependent on the number and nature of the double bonds, especially the number of trisubstituted ones. HBI alkenes with at least one trisubstituted double bond were photodegraded at similar or higher rates than some other lipids (e.g. vitamin E) known to be very reactive towards 1O2. The 1O2 mediated photo-oxidation of HBI alkenes likely involves direct reaction of 1O2 with the trisubstituted double bond via a concerted 'ene' addition, leading to formation of a hydroperoxide at each carbon of the original double bond. The enhanced photoreactivity of HBI alkenes with at least one trisubstituted double bond was confirmed in dead cells of the diatom Haslea ostrearia. In addition, since HBI alkenes with such double bonds were photodegraded at similar or higher rates compared to polyunsaturated fatty acids, vitamin E and chlorophyll a, they should be significantly photochemically altered within the euphotic zone of the ocean. In contrast, HBIs with only di- and monosubstituted double bonds seem to be relatively inert with respect to type II photoprocesses. The results support the apparent good preservation of the monoene IP25 in sediments, while the interpretation of sedimentary occurrences of HBI trienes may need further consideration. © 2011 Elsevier Ltd.


Zabeti N.,Center Doceanologie Of Marseille | Bonin P.,Center Doceanologie Of Marseille | Volkman J.K.,CSIRO | Guasco S.,Center Doceanologie Of Marseille | Rontani J.-F.,Center Doceanologie Of Marseille
Organic Geochemistry | Year: 2010

A number of bacterial strains previously isolated from living cells of the marine haptophyte Emiliania huxleyi and identified from their 16S r-DNA profiles as Dietzia maris sp. S1, Stappia sp. AG2, Nocardioides sp. S3, Sphingomonas sp. AG6, Oceanicaulis alexandrii sp. AG4, O. alexandrii sp. AG7 and Micrococcus sp. AG10 were cultured for examination of their fatty acid (FA) compositions. The total fatty acid (TFA) contents of the different strains ranged from 0.3% to 4% dry wt., which suggests that the use of a single value when converting FA content to estimates of bacterial biomass may have a significant error. A variety of FA distributions was observed, illustrating the diverse patterns in bacteria from marine ecosystems. Some species showed a dominance of saturated and monounsaturated straight chain FAs, while in others iso- and anteiso-branched FAs were the major constituents. The specificity and possible modes of biosynthesis of the unusual constituents, 11-methyloctadec-12-enoic and 10,13-epoxy-11-methyloctadeca-10,12-enoic acids, found in some species, are discussed. Deuterium labelling allowed us to demonstrate that these two compounds arise from the methionine-mediated methylation of cis-vaccenic acid, which supports the previously proposed role of this monounsaturated FA as the precursor of bacterial furan FAs. The strain Sphingomonas sp. AG6 contains C 14-C 16 2-hydroxy acids (strongly dominated by 2-hydroxytetradecanoic acid), which are components of sphingolipid structures linked to sphingosine by amide bonds. 3-Hydroxyacids ranging from C 11 to C 18 were detected in Stappia sp. AG2, O. alexandrii sp. AG4, O. alexandrii sp. AG7 and Micrococcus sp. AG10. These are classical components of cell wall lipopolysaccharides. C 32-C 37 mycolic acids exhibiting an unusually high degree of unsaturation and dominance of odd numbered main chains (>78% of the FAs had a C 21 main chain) were detected in the strain D. maris sp. S1. The data provide further examples of the close association of different types of bacteria with geochemically important algal species. © 2010 Elsevier Ltd.


Boufahja F.,University of Carthage | Vitiello P.,Center Doceanologie Of Marseille | Aissa P.,University of Carthage
Zootaxa | Year: 2014

This work provides an inventory of species of free-living nematodes from Tunisian waters, based on samples collected from September 1977 until March 2013. Sediment samples were taken from 8 ecosystems: the Lagoons of Bizerte, Ghar El Melh and Bou Ghrara, Northern and Southern Lakes of Tunis, Old Harbor of Bizerte, Bizerte Bay and Ichkeul Lake. A total of 31 families, 133 genera, and 249 species of marine nematodes are currently known from Tunisia. The Xyalidae (with 30 species), Cyatholaimidae (25), Chromadoridae and Linhomoeidae (each 21) and Comesomatidae (20) are the richest families. Among them, Daptonema (with 9 species), Pomponema and Sabatieria (with 7 each) are the most spe-cies-rich genera. Some species were recovered only from a specific type of ecosystem. In detail, 109 species were recovered from lagoons, 56 species from sandy beaches and 6 species from mudflats. The 78 remaining species were widely distributed in Tunisian waters and four of these (Terschellingia longicaudata, Oncholaimus campylocercoides, Sabatieria pulchra and Theristus flevensis) were present in most of the 8 ecosystems studied. Copyright © 2014 Magnolia Press.

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