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See detailCyanobacteria from benthic mats of Antarctic lakes as a source of new bioactivities
Biondi, Natascia; Tredici, Mario; Taton, Arnaud et al

in Journal of Applied Microbiology (2008), 105(1), 105-115

Aims: To exploit the cyanobacterial diversity of microbial mats growing in the benthic environment of Antarctic lakes for the discovery of novel antibiotic and antitumour activities. Methods and results ... [more ▼]

Aims: To exploit the cyanobacterial diversity of microbial mats growing in the benthic environment of Antarctic lakes for the discovery of novel antibiotic and antitumour activities. Methods and results: In all, 51 Antarctic cyanobacteria isolated from benthic mats were cultivated in the laboratory by optimizing temperature, irradiance and mixing. Productivity was generally very low (£60 mg l)1 d)1) with growth rates (l) in the range of 0Æ02–0Æ44 d)1. Growth rates were limited by photosensitivity, sensitivity to air bubbling, polysaccharide production or cell aggregation. Despite this, 126 extracts were prepared from 48 strains and screened for antimicrobial and cytotoxic activities. Seventeen cyanobacteria showed antimicrobial activity (against the Gram-positive Staphylococcus aureus, the filamentous fungus Aspergillus fumigatus or the yeast Cryptococcus neoformans), and 25 were cytotoxic. The bioactivities were not in accordance with the phylogenetic grouping, but rather strain-specific. One active strain was cultivated in a 10-l photobioreactor. Conclusions: Isolation and mass cultivation of Antarctic cyanobacteria and LCMS (liquid chromatography ⁄ mass spectrometry) fractionation of extracts from a subset of those strains (hits) that exhibited relatively potent antibacterial and ⁄ or antifungal activities, evidenced a chemical novelty worthy of further investigation. Significance and impact of the study: Development of isolation, cultivation and screening methods for Antarctic cyanobacteria has led to the discovery of strains endowed with interesting antimicrobial and antitumour activities. [less ▲]

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See detailDiversity of planktonic cyanobacteria and microcystin occurrence in Polish water bodies investigated using a polyphasic approach
Boutte, Christophe; Mankiewicz-Boczek, Joanna; Komarkova, Jarka et al

in Aquatic Microbial Ecology (2008), 51

Microscopic measurements of fresh biomass and 16S rRNA gene sequences from clone libraries and denaturing gradient gel electrophoresis (DGGE) were used to investigate cyanobacterial diversity in Polish ... [more ▼]

Microscopic measurements of fresh biomass and 16S rRNA gene sequences from clone libraries and denaturing gradient gel electrophoresis (DGGE) were used to investigate cyanobacterial diversity in Polish water bodies in 2002. In addition, measurements of microcystin (MC) concentrations were made. Thirty water samples were taken from 11 water bodies; of these samples, 18 were obtained from the Sulejow Reservoir during regular monitoring from June to October. Intraand extracellular MC concentrations in Sulejow samples were measured by high performance liquid chromatography (HPLC). The extracellular MC concentration was assessed using a protein phosphatase inhibition assay (PPIA) in additional lakes. Additionally, physicochemical parameters were measured (total nitrogen [TN], total phosphorus [TP], TN:TP ratio, chlorophyll a concentration, temperature). In Sulejow, high intracellular MC concentrations corresponded to large cyanobacterial biovolumes and to low TN:TP ratios. In the other lakes, extracellular MCs were not linked to any measured parameters. The combination of the microscopic and molecular data showed that Aphanizomenon and Microcystis were the dominant genera during the summer period in the Sulejow Reservoir. At the genetic level, there was a succession of 2 different operational taxonomic units (OTUs) belonging to the lineage Anabaena/Aphanizomenon. In the other water bodies, the most frequent populations were Aphanizomenon, Anabaena, Microcystis and Planktothrix. Small populations of Romeria, Snowella, Woronichinia, Limnothrix and Pseudanabaena were observed, and an enigmatic cluster affiliated with Prochlorothrix was genetically retrieved. Anabaena and Microcystis were presumed to be the main genera responsible for the MC production. [less ▲]

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See detailAlgal blooms: emerging problem for health and sustainable use of surface waters
Wilmotte, Annick ULg; Descy, Jean-Pierre; Vyverman, Wim

Report (2008)

The BBLOOMS project was a two-year program, which was primarily proposed to make a first assessment of the extent of present cyanobacterial blooms in Belgium and of the potential threat for the surface ... [more ▼]

The BBLOOMS project was a two-year program, which was primarily proposed to make a first assessment of the extent of present cyanobacterial blooms in Belgium and of the potential threat for the surface water resources. In this study, we addressed several aspects: (i) the extent and phenology of nuisance blooms in multiple-use Belgian surface waters, (ii) the taxonomic diversity of bloom-forming cyanobacteria, using traditional and genetic tools, (iii) the use of genetic markers to estimate whether the organisms are potentially toxic, (iv) the measurement of toxin concentration in field samples, and (v) the relationship between environmental variables and nuisance blooms in selected water bodies. Most field samples came from 4 reference lakes (Blaarmeersen lake in Flanders and three pre-dam lakes of Eau d’Heure in Wallonia) that were monitored intensively for 2 years. Twenty-three samples were taken for Blaarmeersen, in a continuous manner. Seventy-three samples were studied for the Eau d’Heure complex, but only when proliferations were observed. Additional samples were provided by summer samplings in a series of small lakes in Flanders carried out by the University of Gent. As this was insufficient to obtain a global view of the phenomenon, we have built BLOOMNET, a network of water managers and users, who received information about cyanobacterial blooms and how to collect them for subsequent analysis. The network contributed about forty samples from all regions. [less ▲]

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See detailDiversité moléculaire des cyanobactéries planctonniques dans les eaux de surface belges
Lara, Yannick ULg; Lambion, Alexandre ULg; Simon, Patricia ULg et al

Poster (2008, April 02)

Les développements massifs de cyanobactéries ou ‘blooms’ sont devenus un phénomène récurrent et de plus en plus important dans les eaux douces du monde entier durant la dernière décennie. Ces ... [more ▼]

Les développements massifs de cyanobactéries ou ‘blooms’ sont devenus un phénomène récurrent et de plus en plus important dans les eaux douces du monde entier durant la dernière décennie. Ces efflorescences présentent des risques potentiels majeurs pour la santé humaine et animale et interfèrent négativement avec l'utilisation des eaux de surface par exemple, pour le captage d'eau potable, les loisirs nautiques, l'irrigation, les exploitations piscicoles. Entre 25 et 70% des blooms sont toxiques. Comme beaucoup de pays la Belgique n'a pas échappé au problème des efflorescences de cyanobactéries toxiques, mais il y a encore relativement peu de données. Durant la dernière décennie, trois projets européens et nationaux (MIDICHIP 1999-2003, B-BLOOMS 2003-2005, B-BLOOMS 2 2007-2011) se sont intéressés à la diversité des cyanobactéries dans les eaux de surfaces belges. Nous présentons ici un arbre phylogénétique élaboré à partir d’ un pool de 249 séquences partielles du gène codant pour l’ARNr 16S obtenu à partir de 31 échantillons d’eaux belges issus de ces projets. Cet arbre représente la mise à jour d’une base de données qui constitue l’inventaire des cyanobactéries d’eaux douces belges. Cette base de données permet le suivi de l’évolution de la diversité observable de ces organismes en Belgique et la surveillance de l’apparition d’espèces tropicales comme conséquence aux changements climatiques globaux. [less ▲]

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See detailAnalyse bioinformatique de différents marqueurs génétiques pour la caractérisation taxonomique et génotypique des algues bleues.
Lara, Yannick ULg; Wilmotte, Annick ULg

Poster (2008, April)

Les cyanobactéries (ou algues bleues) sont des organismes procaryotes photosynthétiques considérés comme les ancêtres des plastes des végétaux eucaryotes. Présentes dans différents types d’habitats ... [more ▼]

Les cyanobactéries (ou algues bleues) sont des organismes procaryotes photosynthétiques considérés comme les ancêtres des plastes des végétaux eucaryotes. Présentes dans différents types d’habitats terrestres ou aquatiques, elles peuvent produire des composés bioactifs d’intérêt pour des industries pharmaceutiques, ou encore des toxines présentant un risque potentiel pour la santé humaine et animale. Il est donc important de pouvoir caractériser différentes espèces et différents génotypes de ces organismes de manière indubitable pour pouvoir détecter leur présence/absence, évaluer leur rôle au sein de leur écosystème, ainsi que l’influence des facteurs environnementaux sur leur cycle de vie. La caractérisation taxonomique des cyanobactéries a longtemps été réalisée par l’étude des critères morphologiques. Cependant cette approche s’avère délicate quand ces critères peuvent être altérés par la mise en culture. De plus, cette approche requiert une expérience importante et ne permet pas de différencier des génotypes toxiques. La séquence du gène codant pour l’ARN ribosomique 16S est utilisée pour différencier les cyanobactéries jusqu’au genre et parfois jusqu’à l’espèce. Mais, dans certains cas, elle ne coïncide ni avec la description morphologique spécifique, ni avec la production de certaines toxines. Dans le cadre de cette étude, nous proposons d’évaluer l’information taxonomique et génotypique de marqueurs génétiques singuliers présents dans les génomes de cyanobactéries séquencés d la base de données Genbank. Les distances génétiques entre les parties de 32 génomes suffisamment conservées pour être alignées ont été mesurées. Ces distances ont ensuite été comparées par régression linéaire aux distances génétiques de différents loci précis (ARNr 16S, kaiC, lexA, rpoC1, recA). Les résultats préliminaires montrent un R2 de 0,9141 pour la régression linéaire entre les distances génétiques du gène recA et des régions conservées des génomes séquencés appartenant au genre Prochlorococcus. Ce résultat suggère que recA serait potentiellement un bon marqueur pour génotyper des organismes du genre Prochlorococcus. [less ▲]

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See detailAbundance and diversity of picocyanobacteria in High Arctic lakes and fjords
Van Hove, Patrick; Vincent, Warwick; Galland, Pierre et al

in Algological Studies (2008), 168

A series of meromictic lakes, stratified fjords and freshwater lakes at the northern limit of the Canadian High Arctic (northern coastline of Ellesmere Island, Nunavut) were sampled at different depths to ... [more ▼]

A series of meromictic lakes, stratified fjords and freshwater lakes at the northern limit of the Canadian High Arctic (northern coastline of Ellesmere Island, Nunavut) were sampled at different depths to quantify the presence of cyanobacteria and to describe their molecular diversity. The sampled ecosystems spanned a wide span of physico-chemical conditions, with conductivities ranging from freshwater (0.2 mS·cm−1) to seawater (48 mS·cm−1) and temperatures ranging from - 1.91 to 12°C. Fluorescence microscopy cell counts showed that picocyanobacteria occurred in high concentrations (103 to 2.5 × 104 cells·ml−1) in the oxic and suboxic zones of all of these waters. Molecular analysis of the 16S rRNA gene using Denaturating Gradient Gel Electrophoresis (DGGE) and clone libraries of samples from 8 different lakes and fjords revealed a low diversity of picocyanobacteria affiliated to the genus Synechococcus. In total, 132 short sequences from DGGE bands, clones and strains were obtained. Most of the sequences (83 %) clustered in two closely related groups that tend to separate according to saline or freshwater conditions. However, some representatives of each OTU were found in different types of habitat, suggesting some degree of tolerance. These results show that picocyanobacteria are widely distributed under a broad range of physical and chemical conditions in the Arctic environment, and that some genotypes may be specialists that occupy specific habitat types [less ▲]

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See detailCyanobacteria in microbial mats of Antarctic lakes (East Antarctica) - A microscopical approach
Taton, Arnaud; Hoffmann, Lucien; Wilmotte, Annick ULg

in Algological Studies (2008), 168

The cyanobacterial diversity in microbial mats of 56 lakes located in the Larsemann Hills and Bølingen Islands (East Antarctica) was studied by light microscopy. Thirty taxa belonging to 13 genera of ... [more ▼]

The cyanobacterial diversity in microbial mats of 56 lakes located in the Larsemann Hills and Bølingen Islands (East Antarctica) was studied by light microscopy. Thirty taxa belonging to 13 genera of Chroococcales, Oscillatoriales and Nostocales were described. Photomicrographs of the different taxa are provided and their taxonomical assignment as well as their ecology and distribution are discussed. In addition, a semi-quantitative estimation of the abundance of the different morphotypes in the samples was realized and correlated with the mat physiognomy. [less ▲]

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See detailCovariation between zooplankton community composition and cyanobacterial community dynamics in Lake Blaarmeersen (Belgium)
van Gremberghe, Ineke; Van Wichelen, Jeroen; Van der Gucht, Kathleen et al

in FEMS Microbiology Ecology (2008), 63

The cyanobacterial community composition in the mesotrophic Lake Blaarmeersen was determined by denaturing gradient gel electrophoresis (DGGE) of PCRamplified 16S rRNA gene fragments during two ... [more ▼]

The cyanobacterial community composition in the mesotrophic Lake Blaarmeersen was determined by denaturing gradient gel electrophoresis (DGGE) of PCRamplified 16S rRNA gene fragments during two consecutive years to assess the importance of different classes of explanatory variables (bottom-up and top-down factors, physical variables and phytoplankton) in cyanobacterial community dynamics. The most dominant cyanobacteria in Lake Blaarmeersen were Synechococcus (three genotypes), Limnothrix redekei and Anabaena/Aphanizomenon. Analyses of Similarity revealed that the cyanobacterial community in Lake Blaarmeersen differed significantly between the growing season and the winter season as well as between the epilimnion and hypolimnion during the stratified periods. Mantel tests revealed significant correlations between the DGGE data and bottom-up factors, physical variables, the phytoplankton community composition and, interestingly, the zooplankton community composition. In general, the zooplankton community composition (especially the cladoceran community) was more important in structuring the cyanobacterial community than the total zooplankton biomass. This study shows that grazing zooplankton communities can have a relatively strong impact on the cyanobacterial community dynamics and that this impact can be equally important as bottom-up processes regulated by nutrient concentrations and/or physical variables. [less ▲]

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See detailMicrobial communities and carbon fluxes
Warwick, Vincent F; Pedro-Alios, Carlos; Curtis, Suttle et al

in Barber, David; Michaud, Josée; Fortier, Louis (Eds.) On thin ice: a synthesis of the Canadian Arctic Shelf Exchange Study (CASES) (2008)

The CASES program has provided a remarkable opportunity to examine the community structure and seasonal dynamics of microbial communities within coastal Arctic Ocean waters. Through the microbial ... [more ▼]

The CASES program has provided a remarkable opportunity to examine the community structure and seasonal dynamics of microbial communities within coastal Arctic Ocean waters. Through the microbial component of this program, we were able to study the diversity and activities of many forms of microscopic life, including viruses, Archea and Bacteria (known collectively as prokaryotes), and Eukarya (single-celled members, also known as protists). [less ▲]

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See detailDIVERSITY AND HOST SPECIFICITY OF AZOLLA CYANOBIONTS
Papaefthimiou, Dimitra; Van Hove, Charles; Lejeune, André et al

in Journal of Phycology (2008), 44

A unique, hereditary symbiosis exists between the water fern Azolla and cyanobacteria that reside within a cavity in the dorsal leaf-lobe of the plant. This association has been studied extensively, and ... [more ▼]

A unique, hereditary symbiosis exists between the water fern Azolla and cyanobacteria that reside within a cavity in the dorsal leaf-lobe of the plant. This association has been studied extensively, and questions have frequently been raised regarding the number and diversity of cyanobionts (cyanobacterial symbionts) among the different Azolla strains and species. In this work, denaturating gradient gel electrophoresis (DGGE) and a clone library based on the 16S rRNA gene were used to study the genetic diversity and host specificity of the cyanobionts in 35 Azolla strains covering a wide taxonomic and geographic range. DNA was extracted directly from the cyanobacterial packets, isolated after enzymatic digestion of the Azolla leaves. Our results indicated the existence of different cyanobiont strains among Azolla species, and diversity within a single Azolla species, independent of the geographic origin of the host. Furthermore, the cyanobiont exhibited host-species specificity and showed most divergence between the two sections of genus Azolla, Azolla and Rhizosperma. These findings are in agreement with the recent redefinition of the taxon Azolla cristata within the section Azolla. With regard to the taxonomic status of the cyanobiont, the genus Anabaena of the Nostocaceae family was identified as the closest relative by this work. [less ▲]

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See detailAstrobiologie
Javaux, Emmanuelle ULg; Claeys, Philippe; Dehant, Véronique et al

Learning material (2008)

powerpoint sur MyULg, notes partielles imprimées

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See detailAllochthonous inputs of riverine picocyanobacteria to coastal waters in the Arctic Ocean
Waleron, M.; Waleron, Krzysztof ULg; Vincent, W. F. et al

in FEMS Microbiology Ecology (2007), 59(2), 356-365

The observed onset of climate change at high northern latitudes has highlighted the need to establish current baseline conditions in the Arctic Ocean, and has raised concern about the potential for the ... [more ▼]

The observed onset of climate change at high northern latitudes has highlighted the need to establish current baseline conditions in the Arctic Ocean, and has raised concern about the potential for the invasion and growth of biota that have warm temperature optima, such as cyanobacteria. In this study, we used 16S rRNA gene sequences as a molecular marker to evaluate the hypothesis that Arctic rivers provide a major inoculum of cyanobacteria into the coastal Arctic Ocean. Surface samples were collected along a transect extending from the Mackenzie River (Northwest Territories, Canada), across its estuary, to 200 km offshore at the edge of the perennial Arctic pack ice (Beaufort Sea). The highest picocyanobacteria concentrations occurred in the river, with concentrations an order of magnitude lower at offshore marine stations. The 16S rRNA gene clone libraries of five surface samples and five strains along this gradient showed that the cyanobacterial sequences were divided into eight operational taxonomic units (OTUs), six OTUs closely related to freshwater and brackish Synechococcus and two OTUs of filamentous cyanobacteria. No typically marine Synechococcus sequences and no Prochlorococcus sequences were recovered. These results are consistent with the hypothesis of an allochthonous origin of picocyanobacteria in the coastal Arctic Ocean, and imply survival but little net growth of picocyanobacteria under the present conditions in northern high-latitude seas. [less ▲]

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See detailCyanobacteria in cold environments
Zakhia, Frederic; Jungblut, Anne-Dorothee; Taton, Arnaud et al

in Margesin, Rosi; Schinner, Frederic; Marx, Jean-Claude (Eds.) et al 'Psychrophiles: from Biodiversity to Biotechnology (2007)

Cyanobacteria evolved under the harsh conditions of the Precambrian and their modern representatives retain a remarkable ability to adapt to and survive within extreme conditions. They dominate ... [more ▼]

Cyanobacteria evolved under the harsh conditions of the Precambrian and their modern representatives retain a remarkable ability to adapt to and survive within extreme conditions. They dominate terrestrial and freshwater cold ecosystems of the Arctic, Antarctic and alpine regions, even though they do not seem to be specifically adapted to optimal growth at low temperatures. They play a major ecological role as they often are primary colonisers of substrates and major primary producers in these ecosystems. The application of molecular tools in combination with classic morphological techniques has begun to provide new insights into the real diversity of cyanobacteria and their biogeographical distribution in cold environments. Our survey of recent studies suggests complex distributional patterns of cyanobacteria, with cosmopolitan, endemic, and habitat-specific genotypes. This ongoing research will help to identify specific geographical areas that have unique microbial communities. However, many more studies are needed to unravel the enormous diversity of cyanobacteria and to better define their biogeographical patterns in cold environments. This is an urgent task in view of the climatic changes that will undoubtedly alter the structure and functioning of microbial communities in polar and alpine ecosystems. [less ▲]

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See detailMorphological and molecular characterization of planktonic cyanobacteria from Belgium and Luxembourg
Willame, R.; Boutte, C.; Grubisic, Stana ULg et al

in Journal of Phycology (2006), 42(6), 1312-1332

For the first time in Belgium and Luxembourg, the diversity and taxonomy of 95 cyanobacterial strains isolated from freshwater blooms were assessed by the comparison of phenotypes and partial 16S rRNA ... [more ▼]

For the first time in Belgium and Luxembourg, the diversity and taxonomy of 95 cyanobacterial strains isolated from freshwater blooms were assessed by the comparison of phenotypes and partial 16S rRNA gene sequences. The results showed the high diversity of nanoplanktonic, picoplanktonic, and benthic-periphytic cyanobacteria accompanying the main bloom-forming taxa. Indeed, besides 15 morphotypes of bloom-forming taxa, seven non-bloom-forming planktonic morphotypes and 11 morphotypes from benthic-periphytic taxa were isolated in culture from the plankton samples of 35 water bodies. The bloom-forming strains belonged to the genera Microcystis, Woronichinia, Planktothrix, Anabaena, and Aphanizomenon, whereas the other strains isolated from the same samples were assigned to the nanoplanktonic Aphanocapsa, Aphanothece, Snowella, and Pseudanabaena; to the picoplanktonic Cyanobium; and to the benthic periphytic Geitlerinema, Komvophoron, Leptolyngbya, Lyngbya, Phormidium, Calothrix, Nostoc, and Trichormus. The results supported both the polyphyletism of genera such as Aphanocapsa, Aphanothece, Leptolyngbya, Geitlerinema, Anabaena, and Aphanizomenon as well as the validity of genera such as Microcystis, Planktothrix, and Pseudanabaena with gas vesicles and cells constricted at the cross wall. The results obtained showed the close relationship between Snowella and Woronichinia for which very few sequences exist. The first sequence of Komvophoron appeared poorly related to other available cyanobacterial sequences. Although in a few cases a good agreement existed between phenotypic and genotypic features, there was generally a discrepancy. Strains with identical morphotypes show small differences in the 16S rRNA sequences, which might be related to the different chemical properties of their habitats. The results showed the importance of the polyphasic approach in order to improve the taxonomy of cyanobacteria. [less ▲]

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See detailPolyphasic study of Antarctic cyanobacterial strains
Taton, A.; Grubisic, Stana ULg; Ertz, D. et al

in Journal of Phycology (2006), 42(6), 1257-1270

We isolated 59 strains of cyanobacteria from the benthic microbial mats of 23 Antarctic lakes, from five locations in two regions, in order to characterize their morphological and genotypic diversity. On ... [more ▼]

We isolated 59 strains of cyanobacteria from the benthic microbial mats of 23 Antarctic lakes, from five locations in two regions, in order to characterize their morphological and genotypic diversity. On the basis of their morphology, the cyanobacteria were assigned to 12 species that included four Antarctic endemic taxa. Sequences of the ribosomal RNA gene were determined for 56 strains. In general, the strains closely related at the 16S rRNA gene level belonged to the same morphospecies. Nevertheless, divergences were observed concerning the diversity in terms of species richness, novelty, and geographical distribution. For the 56 strains, 21 operational taxonomic units (OTUs, defined as groups of partial 16S rRNA gene sequences with more than 97.5% similarity) were found, including nine novel and three exclusively Antarctic OTUs. Sequences of Petalonema cf. involvens and Chondrocystis sp. were determined for the first time. The internally transcribed spacer (ITS) between the 16S and the 23S rRNA genes was sequenced for 33 strains, and similar groupings were observed with the 16S rRNA gene and the ITS, even when the strains were derived from different lakes and regions. In addition, 48 strains were screened for antimicrobial and cytotoxic activities, and 17 strains were bioactive against the gram-positive Staphylococcus aureus, or the fungi Aspergillus fumigatus and Cryptococcus neoformans. The bioactivities were not in coincidence with the phylogenetic relationships, but rather were specific to certain strains. [less ▲]

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See detailThe cyanophyte Arthrospira fusiformis from Mozambique, Africa: Morphological and molecular characterization
Mussagy, Aidate; Wilmotte, Annick ULg; Cronberg, Gertrud

in Algological Studies (2006), 121

The morphology and the Internally Transcribed Spacer sequences of two Arthrospira (Cyanobacteria) strains with tightly coiled and loosely coiled trichome, isolated from waste water treatment ponds in ... [more ▼]

The morphology and the Internally Transcribed Spacer sequences of two Arthrospira (Cyanobacteria) strains with tightly coiled and loosely coiled trichome, isolated from waste water treatment ponds in Maputo, Mozambique, were investigated. According to the accepted traditional classification the tightly coiled strains were assigned as Arthrospira fusiformis and the loosely coiled as Arthrospira maxima. In both clonal cultures, initiated from a tightly coiled (strain 1) or a loosely coiled trichome (strain 2), different variants arose, in which the tightly coiled forms were more lax than the inoculated cloned trichomes, and loosely coiled forms became tightly coiled. In both cultures, different transient forms appeared, and even straight trichomes were observed. The straight form (variant 1) was isolated and cultivated under different light intensities. After two months, this straight form had not changed into coiled trichomes. However, the trichomes obtained after growth of the hormogonia of the straight trichomes contained a mixture of loosely coiled and straight trichomes.On the basis of the morphological analysis of Arthrospira, it is evident that the degree of coiling is highly variable, which creates uncertainty when used to define the different species. The DNA from the two clonal strains 1 and 2 was isolated and a part of the rRNA operon (including the 3' end of the 16S rRNA gene and the Internally Transcribed Spacer) was determined after amplification by PCR using specific primers. The two ITS sequences were identical and belonged to the subcluster I.A., as defined by Baurain et al. (2002). Variant 1 gave also an identical ITS sequence. A PCR to test the presence of mcyE, a gene involved in the synthesis of the microcystin synthetase, was negative for the two strains and the variant 1. This study showed that for a reliable identification of Arthrospira species, information from specimens collected in the field, cultured strains, developmental stages, and molecular analysis, should be combined. [less ▲]

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See detailBiogeographical distribution and ecological ranges of benthic cyanobacteria in East Antarctic lakes
Taton, A.; Grubisic, Stana ULg; Balthasart, Pierre ULg et al

in FEMS Microbiology Ecology (2006), 57(2), 272-289

For the first time, the cyanobacterial diversity from microbial mats in lakes of Eastern Antarctica was investigated using microscopic and molecular approaches. The present study assessed the ... [more ▼]

For the first time, the cyanobacterial diversity from microbial mats in lakes of Eastern Antarctica was investigated using microscopic and molecular approaches. The present study assessed the biogeographical distribution of cyanobacteria in Antarctica. Five samples were taken from four lakes spanning a range of different ecological environments in Larsemann Hills, Vestfold Hills and Rauer Islands to evaluate the influence of lake characteristics on the cyanobacterial diversity. Seventeen morphospecies and 28 16S rRNA gene-based operational taxonomic units belonging to the Oscillatoriales, Nostocales and Chroococcales were identified. The internal transcribed spacer was evaluated to complement the 16S rRNA gene data and showed similar but more clear-cut tendencies. The molecular approach suggested that potential Antarctic endemic species, including a previously undiscovered diversity, are more abundant than has been estimated by morphological methods. Moreover, operational taxonomic units, also found outside Antarctica, were more widespread over the continent than potential endemics. The cyanobacterial diversity of the most saline lakes was found to differ from the others, and correlations between the sampling depth and the cyanobacterial communities can also be drawn. Comparison with database sequences illustrated the ubiquity of several cyanobacterial operational taxonomic units and their remarkable range of tolerance to harsh environmental conditions. [less ▲]

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