[show abstract][hide abstract] 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 08/2013; 14(6). · 2.18 Impact Factor
[show abstract][hide abstract] ABSTRACT: The intracellular biosynthesis of superparamagnetic (blocking temperature 5.6K) 2-lines ferrihydrite (Fh2L) nanoparticles was observed within living Euglena gracilis microalgae.
[show abstract][hide abstract] 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
[show abstract][hide abstract] 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
[show abstract][hide abstract] 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
[show abstract][hide abstract] 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.
[show abstract][hide abstract] 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
[show abstract][hide abstract] 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 .
[show abstract][hide abstract] 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. · 1.60 Impact Factor
[show abstract][hide abstract] 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.
[show abstract][hide abstract] ABSTRACT: Common Anabaena, Calothrix, and Leptolyngbya cyanobacteria are shown to form Au, Ag, Pd, and Pt nanoparticles of well-controlled size. These nanoparticles are synthesized intra-cellularly, and naturally released in the culture medium, where they are stabilized by algal polysaccharides, allowing their easy recovery. The size of the recovered particles as well as the reaction yield is shown to depend on the cyanobacteria genus. Investigations of nanoparticle formation indicate that the intracellular nitrogenase enzyme is responsible for the metal reduction but that the cellular environment is involved in the colloid growth process.
Journal of Nanoscience and Nanotechnology 09/2007; 7(8):2696-708. · 1.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: This paper deals with the taxonomic and nomenclatural revision of some species and infraspecific taxa of the genus Trachelomonas (Euglenophyceae). Twelve changes are suggested. Among them, we propose new synonyms for the following four taxa: Trachelomonas acanthophora var. minor Balech et Dastugue, T. acanthophora var. speciosa (Defl.) Balech, T. hispida (Perty) Stein emend. Defl. and T. superba var. swirenkiana Defl.; the identification of an unnamed but previously illustrated and described individual: T. amphoriformis var. granulosa Couté et Iltis; a new variety: T. megalacantha da Cunha var. paucispina Couté et Tell, and five new status and new combinations: T. crateriphora (Conforti et Ruiz) Couté et Tell, T. duplex (Defl.) Couté et Tell, T. rugulosa var. paralella fo. paralella (Tell et Zalocar) Couté et Tell and T. rugulosa var. paralella fo. minima (Conforti et Ruiz) Couté et Tell.
[show abstract][hide abstract] ABSTRACT: Algae and cyanobacteria in biofilms cause discolouration of the building surfaces they colonise. In France, no comprehensive study of the diversity of the species involved in this phenomenon has up to now been undertaken. 71 samples were therefore collected all over France and analysed for their micro-organisms composition. Green algae were the most frequent organisms encountered, with Klebsormidium flaccidum (55 %), Trebouxia spp. (49 %), Stichococcus bacillaris (46 %), Chlorosarcinopsis minor (28 %) and Chlorella cf. mirabilis (27 %) being the most abundant ones. Colonial cyanobacteria were then mainly represented by Cyanosarcina parthenonensis (28 %), Chroococcus lithophilus (21 %), Gloeocapsa sanguinea (15 %) and filamentous cyanobacteria by Calothrix pulvinata (21 %), Leptolyngbya foveolarum (18 %) and Phormidium corium (13 %).
[show abstract][hide abstract] ABSTRACT: Algae and cyanobacteria are colonisers of building façades. A multivariate analysis of data gathered during a sampling campaign around France proved that precipitation, hygrometry, thermal amplitude, distance from the sea and proximity to vegetation were environmental parameters influencing this colonisation. Other influencing factors could be attributed to the nature of the façade coating, mineral substrata being more frequently colonised, and to the architecture, favouring in some cases the formation of damp conditions and thus the colonisation of the building envelope.