Alain Couté

Muséum National d'Histoire Naturelle, Lutetia Parisorum, Île-de-France, France

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Publications (77)126.16 Total impact

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    ABSTRACT: Nuclear activities generate radioactive elements which require processes for their decontamination. Although biological remediation has proved efficient in industrial applications, no biotechnology solution is currently operational for highly radioactive media. Such a solution requires organisms that accumulate radionuclides while withstanding radioactivity. This paper describes the potentialities of an extremophile autotrophic eukaryote, Coccomyxa actinabiotis nov. sp., that we isolated from a nuclear facility and which withstands huge ionizing radiation doses, up to 20000 Gy. Half the population survives 10000 Gy, which is comparable to the hyper-radioresistant well-known prokaryote Deinococcus radiodurans. Cell metabolic profile investigated by nuclear magnetic resonance was hardly affected by radiation doses of up to 10000 Gy. Cellular functioning completely recovered within a few days. This outstanding microalga also strongly accumulates radionuclides, including 238U, 137Cs, 110mAg, 60Co, 54Mn, 65Zn, and 14C (decontamination above 85% in 24 h, concentration factor, 1000-450000 mL g-1 fresh weight). In 1 h, the microalga revealed as effective as the conventional physico-chemical ion-exchangers to purify nuclear effluents. Using this organism, an efficient real-scale radionuclide bio-decontamination process was performed in a nuclear fuel storage pool with hundred-fold waste volume reduction compared to the usual physico-chemical process. The feasibility of new decontamination solutions for the nuclear industry and for environmental clean-up operations is demonstrated.
    Energy & Environmental Science 04/2013; 6(4):1230-1239. · 11.65 Impact Factor
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    ABSTRACT: The invention relates to novel algae of the Coccomyxa genus, in particular the algae of a novel species called Coccomyxa actinabiotis, and to the use thereof for metal uptake from aqueous media, and in particular from radioactive media.
    Ref. No: US20130078707, Year: 03/2013
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    ABSTRACT: The intracellular biosynthesis of superparamagnetic (blocking temperature 5.6K) 2-lines ferrihydrite (Fh2L) nanoparticles was observed within living Euglena gracilis microalgae.
    Colloids and surfaces B: Biointerfaces 05/2012; 93:20-3. · 3.55 Impact Factor
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    ABSTRACT: The design of cell-based bioreactors for inorganic particles formation requires both a better understanding of the underlying processes and the identification of most suitable organisms. With this purpose, the process of Au3+ incorporation, intracellular reduction, and Au0 nanoparticle release in the culture medium was compared for four photosynthetic microorganisms, Klebsormidium flaccidum and Cosmarium impressulum green algae, Euglena gracilis euglenoid and Anabaena flos-aquae cyanobacteria. At low gold content, the two green algae show maintained photosynthetic activity and recovered particles (ca. 10 nm in size) are similar to internal colloids, indicating a full biological control over the whole process. In similar conditions, the euglenoid exhibits a rapid loss of biological activity, due to the absence of protective extracellular polysaccharide, but could grow again after an adaptation period. This results in a larger particle size dispersity but larger reduction yield. The cyanobacteria undergo rapid cell death, due to their prokaryotic nature, leading to high gold incorporation rate but poor control over released particle size. Similar observations can be made after addition of a larger gold salt concentration when all organisms rapidly die, suggesting that part of the process is not under biological control anymore but also involves extracellular chemical reactions. Overall, fruitful information on the whole biocrystallogenesis process is gained and most suitable species for further bioreactor design can be identified, i.e., green algae with external coating.
    Journal of Nanoparticle Research 01/2012; 14(6). · 2.18 Impact Factor
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    ABSTRACT: Targeting the development of cell-based bioreactors for the production of metal nanoparticles, the possibility to perform the sustained synthesis of colloidal gold using Klebsormidium flaccidum green algae was studied. A first strategy relying on successive growth/reduction/reseeding recycling steps demonstrated maintained biosynthesis capability of the microalgae but limitation in metal content due to toxic effects. An alternative approach consisting of progressive gold salt addition revealed to be suitable to favor cell adaptation to larger metal concentrations and supported particle release over month periods.
    Biotechnology and Bioengineering 08/2011; 109(1):284-8. · 3.65 Impact Factor
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    ABSTRACT: Fighting against water pollution requires the ability to detect pollutants for example herbicides or heavy metals. Micro-algae that live in marine and fresh water offer a versatile solution for the construction of novel biosensors. These photosynthetic microorganisms are very sensitive to changes in their environment, enabling the detection of traces of pollutants. Three groups of micro-algae are described in this paper: chlorophyta, cyanobacteria, and diatoms.
    Analytical and Bioanalytical Chemistry 05/2011; 401(2):581-97. · 3.66 Impact Factor
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    ABSTRACT: The potential ecotoxicity of nanosized cadmium sulfide (CdS), synthesized by the polyol process, was investigated using common Anabaena flos-aquae cyanobacteria and Euglena gracilis euglenoid microalgae. The photosynthetic activities of these microorganisms, after addition of free Cd2+ ions and CdS nanoparticles, varied with the presence of tri-n-octylphosphine oxide (TOPO) used to protect surface particle to avoid toxicity and also to control particle size and shape during the synthesis. The nanoparticle concentration was varied from 10(-3) to 5 x 10(-4) M. It was observed that the cadmium concentration, the addition of TOPO protective agent and the particle dissolution process in the culture medium play an important role during the ecotoxicological tests. Viability tests were followed by PAM fluorimetry. Cd2+ ions were very toxic for Anabaena flos aquae. The same behavior was observed after contact with CdS and CdS-TOPO nanoparticles. However, for Euglena gracilis, the photosynthetic activity was stable for more than 1 month in the presence of Cd2+ ions. Moreover, it was observed that the toxicity varies with the concentration of CdS and CdS-TOPO nanoparticles, both kind of nanoparticles are toxic for this microorganism. Transmission electron microscopy (TEM) analyses of microorganisms ultrathin sections showed that polysaccharides produced by Anabaena flos-aquae, after contact with CdS and CdS-TOPO nanoparticles, protect the microalgae against particle internalization. Only some particles were observed inside the cells. Moreover, the nanoparticle internalization was observed after contact with all nanoparticles in the presence of Euglena gracilis by endocytosis. All nanoparticles are inside vesicles formed by the cells.
    Journal of Nanoscience and Nanotechnology 03/2011; 11(3):1852-8. · 1.15 Impact Factor
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    ABSTRACT: The potential ecotoxicological impact of ZnO nanostructured films was investigated using common Anabaena flos-aquae, Calothrix pulvinata cyanobacteria and Euglena gracilis euglenoid microalgae. The pre-formed ZnO nanoparticles were synthesized in di(ethylene glycol) medium by forced hydrolysis of ionic Zn2+ salts. Particle size and shape were controlled by addition of protective agents such as tri-n-octylphosphine oxide and polyoxyethylene stearyl ether. ZnO nanostructured films were directly prepared by spray deposition of pre-formed polyol-based ZnO nanoparticles (ZnO, ZnO-TOPO and ZnO-Brij-76) at 250 °C heated glass substrate. Another sample was prepared from zinc acetate in di(ethylene glycol) diluted in ethanol medium without nanoparticles (ZnO-SOL). In this case, ZnO nanostructured film was formed directly on the glass substrate at the same temperature. Water contact angle on ZnO-based films showed that nanostructured ZnO films containing ZnO nanoparticles prepared without protective agent or with tri-n-octylphosphine oxide present a hydrophobic character while the ones containing nanoparticles prepared using polyoxyethylene stearyl ether or the control sample are hydrophilic. Here we showed that (i) the use of protective agents, (ii) the surface properties of the films and (iii) the nature of the biological system can strongly influence the ecotoxicological studies. Epifluorescence microscopy analyses and Live/Dead tests showed that all films are toxic for Euglena gracilis. In the case of Anabaena flos-aquae and Calothrix pulvinata, tri-n-octylphosphine oxide and polyoxyethylene stearyl ether molecules can prevent ZnO nanoparticle toxicity.
    Thin Solid Films 01/2011; · 1.87 Impact Factor
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    ABSTRACT: The invention relates to novel algae of the Coccomyxa genus, in particular the algae of a novel species called Coccomyxa actinabiotis, and to the use thereof for metal uptake from aqueous media, and in particular from radioactive media.
    Ref. No: WO 2011/098979, Year: 01/2011
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    ABSTRACT: Klebsormidium flaccidum algalcells exhibiting the ability to form gold nanoparticles intra-cellularly in suspension were encapsulated within silica gels. Optical and electronic microscopy indicate that entrapped cells maintain their ability to reduce gold salts. A difference in the kinetics of gold colloid formation within silica in the absence or presence of cells could be followed by UV-visible absorption spectroscopy, confirming the bio-mediated nature of the reduction process. Study of the photosynthetic activity of the algae showed that the encapsulation process protects the cells from lethal effects arising from gold toxicity. Moreover, the first in situ imaging of entrapped cells using Raman spectroscopy allowed the investigation of the influence of the gold colloids on the photosynthetic system of the algae, in particular through modification of chlorophyll fluorescence and carotenoid signals. Such a coupling of sol–gel encapsulation and Raman imaging should allow the future development of novel photosynthesis-based cellular biosensors.
    Journal of Materials Chemistry 10/2010; · 5.97 Impact Factor
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    ABSTRACT: To date, phylogenies have been based on known gene sequences accessible at GenBank, and the absence of many cyanobacterial lineages from collections and sequence databases has hampered their classification. Investigating new biotopes to isolate more genera and species is one way to enrich strain collections and subsequently enhance gene sequence databases. A polyphasic approach is another way of improving our understanding of the details of cyanobacterial classification. In this work, we have studied phylogenetic relationships in strains isolated from freshwater bodies in Senegal and Burkina Faso to complement existing morphological and genetic databases. By comparing 16S rDNA sequences of African strains to those of other cyanobacteria lineages, we placed them in the cyanobacterial phylogeny and confirmed their genus membership. We then focused on the Nostocaceae family by concatenated analysis of four genes (16S rDNA, hetR, nifH, and rpoC1 genes) to characterize relationships among Anabaena morphospecies, in particular, Anabaena sphaerica var. tenuis G. S. West. Using a polyphasic approach to the Nostocaceae family, we demonstrate that A. sphaerica var. tenuis is more closely related to Cylindrospermospsis/Raphidiopsis than to other planktonic Anabaena/Aphanizomenon. On the basis of phylogeny and morphological data, we propose that these three significantly different clusters should be assigned to three genera.
    Journal of Phycology 05/2010; 46(3):564 - 579. · 2.24 Impact Factor
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    ABSTRACT: The potential ecotoxicity of nanosized zinc oxide (ZnO), synthesized by the polyol process, was investigated using common Anabaena flos-aquae cyanobacteria and Euglena gracilis euglenoid microalgae. The photosynthetic activities of these microorganisms, after addition of ZnO nanoparticles, varied with the presence of protective agents such as tri-n-octylphosphine oxide (TOPO) and polyoxyethylene stearyl ether (Brij-76) used to control particle size and shape during the synthesis. In the case of Anabaena flos-aquae , the photosynthetic activity, after addition of ZnO, ZnO-TOPO, and ZnO-Brij-76, decreased progressively due to stress induced by the presence of the nanoparticles in the culture medium. After contact with ZnO-TOPO nanoparticles, this decrease was followed by cell death. On the other hand, after 10 days, a progressive increase of the photosynthetic activity was observed after contact with ZnO and ZnO-Brij-76 nanoparticles. In the case of Euglena gracilis , cell death was observed after contact with all nanoparticles. Transmission electron microscopy (TEM) analyses of ultrathin sections of microorganisms showed that polysaccharides produced by Anabaena flos-aquae avoid particle internalization after contact with ZnO and ZnO-Brij-76 nanoparticles. On the other hand, nanoparticle internalization was observed after contact with all nanoparticles in the presence of Euglena gracilis and also with ZnO-TOPO nanoparticles after contact with Anabaena flos-aquae .
    Langmuir 03/2010; 26(9):6522-8. · 4.38 Impact Factor
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    ABSTRACT: Common Anabaena cyanobacteria are shown to form intra-cellularly akaganeite β-FeOOH nanorods of well-controlled size and unusual morphology at room temperature. High-resolution transmission electron microscopy showed that these nanorods present a complex arrangement of pores forming a spongelike structure. These hybrid akaganeite-cyanobacteria were used to form “one-pot” hybrid biofilms. The hybrid biofilm presents higher coercivity (Hc=44.6kAm−1 (560Oe)) when compared to lyophilized akaganeite-cyanobacteria powder (Hc=0.8kAm−1 (10Oe)) due to the quasi-assembly of the cells on the glass substrate compared to the lyophilized randomly akaganeite-cyanobacteria powder.
    Thin Solid Films 01/2010; 518(19):5432-5436. · 1.87 Impact Factor
  • 28eme colloque de l'ADLAF, Banyuls; 09/2009
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    ABSTRACT: Common Anabaena and Calothrix cyanobacteria and Klebsormidium green algae are shown to form intracellularly akaganeite beta-FeOOH nanorods of well-controlled size and unusual morphology at room temperature. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy X-ray energy dispersive spectrometry (SEM-EDS) analyses are used to investigate particle structure, size, and morphology. A mechanism involving iron-siderophore complex formation is proposed and compared with iron biomineralization in magnetotactic bacteria.
    Langmuir 08/2009; 25(17):10062-7. · 4.38 Impact Factor
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    ABSTRACT: Micro-organisms living in extreme environments are captivating in the peculiar survival processes they have developed. Deinococcus radiodurans is probably the most famous radio-resistant bacteria. Similarly, a specific ecosystem has grown in a research reactor storage pool, and has selected organisms which may sustain radiative stress. An original green micro-alga which was never studied for its high tolerance to radiations has been isolated. It is the only autotrophic eukaryote that develops in this pool, although contamination possibilities coming from outside are not unusual. Studying what could explain this irradiation tolerance is consequently very interesting. An integrative study of the effects of irradiation on the micro-algae physiology, metabolism, internal dynamics, and genomics was initiated. In the work presented here, micro-algae were stressed with irradiation doses up to 20 kGy (2 Mrad), and studied by means of nuclear magnetic resonance, looking for modifications in the metabolism, and on the IN13 neutron backscattering instrument at the ILL, looking for both dynamics and structural macromolecular changes in the cells.
    Journal of Physics Condensed Matter 02/2008; · 2.22 Impact Factor

Publication Stats

677 Citations
126.16 Total Impact Points

Institutions

  • 1978–2013
    • Muséum National d'Histoire Naturelle
      Lutetia Parisorum, Île-de-France, France
  • 2007–2012
    • Paris Diderot University
      • Interfaces, Traitements, Organisation et Dynamique des Systèmes (ITODYS) UMR 7086
      Lutetia Parisorum, Île-de-France, France
  • 2006–2012
    • Muséum d’Histoire Naturelle de Toulon et du Var
      Toulon-sur-Mer, Provence-Alpes-Côte d'Azur, France
    • Centre Scientifique et Technique du Bâtiment
      Lutetia Parisorum, Île-de-France, France
  • 2001
    • French National Institute for Agricultural Research
      Lutetia Parisorum, Île-de-France, France
  • 1999
    • Université d'Orléans
      • Institut des Sciences de la Terre d'Orléans (ISTO)
      Orléans, Centre, France