Diversity of algae and cyanobacteria growing on building façades in France

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 %).Fil: Barberousse, Hélène. Museum National D'histoire Naturelle; Francia. Centre Scientifique et Technique du Bâtiment; FranciaFil: Tell, Hector Guillermo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Laboratorio de Limnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Yéprémian, Claude. Museum National D'histoire Naturelle; FranciaFil: Couté, Alain. Museum National D'histoire Naturelle; Franci

Ecotoxicological Studies of ZnO and CdS Nanoparticles on Chlorella vulgaris Photosynthetic Microorganism in Seine River Water

International audienceSeine river water was used as natural environmental medium to study the ecotoxicological impact of ZnO and CdS nanoparticles and Zn 2+ and Cd 2+ free ions using Chlorella vulgaris as a biological target. It was demonstrated by viability tests and photosynthetic activity measurements that free Zn 2+ (IC 50 = 2.7 × 10 −4 M) is less toxic than free Cd 2+ and ZnO nanoparticles (IC 50 = 1.4 × 10 −4 M). In the case of cadmium species, free Cd 2+ (IC 50 = 3.5 × 10 −5 M) was similar to CdS nanoparticles (CdS-1: IC 50 = 1.9 × 10 −5 M and CdS-2: IC 50 = 1.9 × 10 −5 M), as follows: CdS > Cd 2+ > ZnO > Zn 2+. Adenosine-5'-triphosphate (ATP) assay and superoxide dismutase (SOD) enzymatic activity confirmed these results. Transmission electron microscopy (TEM), coupled with energy-dispersive X-ray spectroscopy (EDS), confirmed the internalization of CdS-1 nanoparticles after 48 h of contact with Chlorella vulgaris at 10 −3 M. With a higher concentration of nanoparticles (10 −2 M), ZnO and CdS-2 were also localized inside cells

Effects of microcystin-producing and microcystin-free strains of

The effects of cyanobacterial toxins on herbivorous zooplankton depend on cyanobacterial strains, zooplankton species and environmental conditions. To explore the relationship between zooplankton and cyanobacteria, we investigated the effects of Planktothrix agardhii extracts on Daphnia magna population dynamics. We designed an experiment where individuals were grown in the presence of extracts of two P. agardhii strains. We monitored daily life-history parameters of D. magna individuals subjected to microcystin-RR (MC-RR), intracellular and extracellular extracts of a microcystin-producing strain (MC-strain, PMC 75.02) and a microcystin-free strain (MC-free strain, PMC 87.02) of P. agardhii. Measured life-history parameters of D. magna were used to build population dynamics models and compute expected population growth rate, replacement rate, generation time and proportion of adult and juveniles at demographic equilibrium. Results show that MC-RR tends to slow the life history (reduced growth rate and larger proportion of adults). In contrast, intracellular extracts of the two strains tend to accelerate the life history (increased growth rate, decreased generation time and lower proportion of adults). Extracellular extracts produce the same trends as the intracellular extracts but to a lesser extent. However, the MC-strain has stronger effects than the MC-free strain. Interestingly, extracellular extracts of the MC-free strain may have effects comparable to pure MC-RR. Moreover, in the presence of MC-RR and both cyanobacterial extracts, the daily fecundities present a cyclic pattern. These results suggest that MC-RR and unknown metabolites of cyanobacterial extracts have negative effects on D. magna reproduction processes such as those observed with endocrine-disruptive molecules

To flee or not to flee: detection, avoidance and attraction of profitable resources by Daphnia magna studied with olfactometer

<p><em>The cladoceran herbivore </em>Daphnia magna <em>is a major consumer of phytoplankton in lakes. Therefore, this organism may control the phytoplankton community and the proliferation of some algae or cyanobacteria. Cladoceran behaviour and migration in relation to temperature, light or presence of planktivorous fishes have been well studied. In particular, it is known that the detection of kairomones produced by predators may induce avoidance. Avoidance could also occur with other semiochemicals such as cyanotoxins. In order to explore this hypothesis, we used an olfactometer to observe and measure the exploratory behaviour of </em>D. magna <em>individuals based on the motivation for food. Daphnids were allowed to choose between different compounds: water, a pure cyanotoxin, </em>i.e. <em>the microcystin-RR [(MC)-RR], extracts of one MC-producing strain (PMC 75.02) and one MC-free strain (PMC 87.02) of </em>Planktothrix agardhii<em>, or a green algae </em>Scenedesmus obliquus<em>. With this experimental design, we observed that i) cladocerans are able to detect resources with different qualities, ii) they can explore before exhibiting preferences, and iii) daphnids are able to avoid compounds that are potentially toxic (</em>e.g., <em>microcystins). First, daphnids explored the environment, subsequently (after about 1.5 h), they showed a significant tendency to stay where there is a profitable resource such as </em>S. obliquus<em>. These results also suggest that specimens of </em>D. magna <em>cannot detect MC compounds from </em>P. agardhii<em>, but they respond to it as a food resource. The study of zooplankton ability to explore the environment when exposed to semiochemicals needs further investigation</em>.</p><p> </p

Improvement of kinetics, yield, and colloidal stability of biogenic gold nanoparticles using living cells of Euglena gracilis microalga

International audienceRecent years have witnessed a boom in the biosynthesis of a large variety of nanomaterials using different biological resources among which algae-based entities have been gaining much more attention within the community of material scientists worldwide. In our previously published findings, we explored some factors that governed the biofabrication of gold nanoparticles using living cultures of microalgae, such as the utilized microalgal genera, the phylum they belong to, and the impact of tetrachloroauric acid concentrations on the ability of these strains to perform the biosynthesis of gold nanoparticles once in contact with these cations. As a follow-up, we present in this paper an improvement of the features of bioproduced gold colloids using living cells of Euglena gracilis microalga when this species is grown under either mixotrophic or autotrophic conditions, i.e., exposed to light and grown in an organic carbon-enriched culture medium versus under autotrophic conditions. As an outcome to this alteration, the growth rate of this photosynthetic microorganism is multiplied 7–8 times when grown under mixotrophic conditions compared to autotrophic ones. Therefore, the yield, the kinetics, and the colloidal stability of the biosynthesized gold nanoparticles are dramatically enhanced. Moreover, the shape and the size of the as-produced nano-objects via this biological method are affected. In addition to round-shaped gold nanoparticles, particular shapes, such as triangles and hexagons, appear. These findings add up to the amassed knowledge toward the design of photobioreactors for the scalable and sustainable production of interesting nanomaterials

Drivers and ecological consequences of dominance in periurban phytoplankton communities using networks approaches

International audienceEvaluating the causes and consequences of dominance by a limited number of taxa in phytoplankton communities is of huge importance in the current context of increasing anthropogenic pressures on natural ecosystems. This is of particular concern in densely populated urban areas where usages and impacts of human populations on water ecosystems are strongly interconnected. Microbial biodiversity is commonly used as a bioindicator of environmental quality and ecosystem functioning, but there are few studies at the regional scale that integrate the drivers of dominance in phytoplankton communities and their consequences on the structure and functioning of these communities. Here, we studied the causes and consequences of phytoplankton dominance in 50 environmentally contrasted waterbodies, sampled over four summer campaigns in the highly-populatedÎle-de-France region (IDF). Phytoplankton dominance was observed in 32e52% of the communities and most cases were attributed to Chlorophyta (35.5 e40.6% of cases) and Cyanobacteria (30.3e36.5%). The best predictors of dominance were identified using multinomial logistic regression and included waterbody features (surface, depth and connection to the hydrological network) and water column characteristics (total N, TN:TP ratio, water temperature and stratification). The consequences of dominance were dependent on the identity of the dominant organisms and included modifications of biological attributes (richness, cohesion) and functioning (biomass, RUE) of phytoplankton communities. We constructed co-occurrence networks using high resolution phytoplankton biomass and demonstrated that networks under dominance by Chlorophyta and Cyanobacteria exhibited significantly different structure compared with networks without dominance. Furthermore, dominance by Cyanobacteria was associated with more profound network modifications (e.g. cohesion, size, density, efficiency and proportion of negative links), suggesting a stronger disruption of the structure and functioning of phytoplankton communities in the conditions in which this group dominates. Finally, we provide a synthesis on the relationships between environmental drivers, dominance status, community attributes and network structure

Fate of ZnS:Mn quantum dots in Seine River water and seawater. Ecotoxicological effects on Chlorella Vulgaris microalgae

The release of engineered materials into the environment can have detrimental effects on living organisms in ground, rivers, and oceans. Despite the increasing use of nanomaterials, little research is conducted on their degradation. Understanding the biology and environmental consequences of manufactured materials is crucial for preserving the environment and developing more respectful chemistry protocols. Physicochemical studies are essential to understand material behavior and their uptake and distribution within microorganisms. II-VI semiconducting nanocrystals, like ZnS nanoparticles, have emerged due to their quantum confinement, allowing for customization of electronic and optical properties. To assess the toxicity of ZnS QDs doped with Mn2+ and perform ecotoxicological tests, a suitable natural environment and an aquatic model are needed. Microalgae, like Chlorella Vulgaris, offer advantages in ecotoxicology, including environmental relevance, sensitivity, experimental feasibility, ethical considerations, and comparative studies. This paper presents the synthesis of ZnS:Mn NPs with varying concentrations of Mn2+. These NPs induce an antioxidant defense system in algal cells, which may be toxic to Chlorella vulgaris via an oxidative stress mechanism. The toxicity of manganese-doped ZnS nanoparticles does exist but is lower than that induced by a Mn2+ ion concentration of 100 mg L-1

A global approach of the mechanism involved in the biosynthesis of gold colloids using micro-algae

International audienceThe use of micro-algae for the production of noble metal nanoparticles has drawn much attention recently. This paper aims to address some questions raised by our earlier publications and some recent reports from other groups, among which the biological pathways involved in the bioreduction of noble metal cations into nanoparticles and the design of stable colloids. TEM micrographs, taken at the early stage of contact between cells and salt solutions, show undoubtedly that the biomineralization process occurs within the thylakoidal membranes, which are the organelles responsible for photosynthesis. We strongly believe that the available enzymes and their cofactors (enzymatic machinery) are the key molecules that allow such reduction, promoting therefore the formation of nanoparticles. In addition, by comparing the characteristics of gold colloids made by polysaccharides-producing and non-producing micro-algae strains, we demonstrate that the stability of those colloids is ensured predominantly by those biopolymers. These macrobiomolecules control partly the size and the shape of NPs

The physics and chemistry of silica-in-silicates nanocomposite hydrogels and their phycocompatibility

International audienceSilicates-in-silica nanocomposite hydrogels obtained from sodium silicates/colloidal silica mixtures have previously been found to be useful for bacterial encapsulation. However the extension of synthesis conditions and the understanding of their impact on the silica matrix would widen the applicability of this process in terms of encapsulated organisms and the host properties. Here the influence of silicates and the colloidal silica concentration as well as pH conditions on the gel time, the optical properties, the structural and mechanical properties of silica matrices was studied. We show that gel formation is driven by silicate condensation but that the aggregation of silica colloids also has a major influence on the transparency and structure of the nanocomposites. Three different photosynthetic organisms, cyanobacteria Anabaena flos-aquae and two microalgae Chorella vulgaris and Euglena gracilis, were used as probes of the phycocompatibility of the process. The three organisms were highly sensitive to the silicate concentration, which impacts both the gelation time and ionic strength conditions. The Ludox content was crucial for cyanobacteria as it strongly impacts the Young's modulus of the matrices. The detrimental effect of acidic pH on cell suspension was compensated by the silica network. Overall, it is now possible to select optimal encapsulation conditions based on the physiology of the targeted cells, opening wide perspectives for the design of biosensors and bioreactors

Identification of Cyanobacteria and Its Potential Toxins in the Joanes I Reservoir, Bahia, Brazil

The Joanes I Reservoir is responsible for 40% of the drinking water supply of the Metropolitan Region of Salvador, Bahia, Brazil. For water sources such as this, there is concern regarding the proliferation of potentially toxin-producing cyanobacteria, which can cause environmental and public health impacts. To evaluate the presence of cyanobacteria and their cyanotoxins in the water of this reservoir, the cyanobacteria were identified by microscopy; the presence of the genes of the cyanotoxin-producing cyanobacteria was detected by molecular methods (polymerase chain reaction (PCR)/sequencing); and the presence of toxins was determined by liquid chromatography with tandem mass spectrometry (LC-MS/MS). The water samples were collected at four sampling points in the Joanes I Reservoir in a monitoring campaign conducted during the occurrence of phytoplankton blooms, and the water quality parameters were also analysed. Ten cyanobacteria species/genera were identified at the monitoring sites, including five potentially cyanotoxin-producing species, such as Cylindrospermopsis raciborskii, Cylindrospermopsis cf. acuminato-crispa, Aphanocapsa sp., Phormidium sp., and Pseudanabaena sp. A positive result for the presence of the cylindrospermopsin toxin was confirmed at two sampling points by LC-MS/MS, which indicated that the populations are actively producing toxins. The analysis of the PCR products using the HEPF/HEPR primer pair for the detection of the microcystin biosynthesis gene mcyE was positive for the analysed samples. The results of this study point to the worrisome condition of this reservoir, from which water is collected for public supply, and indicate the importance of the joint use of different methods for the analysis of cyanobacteria and their toxins in reservoir monitoring