Laure Guillou

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Syndiniales are a parasitic order within the eukaryotic lineage Dinophyceae (Alveolata). Here, we analysed the taxonomy of this group using 43655 18S rRNA gene sequences obtained either from environmental data sets or cultures, including 6874 environmental sequences from this study derived from Atlantic and Mediterranean waters. A total of 5571 out of the(More)
Culture-independent molecular analyses of open-sea microorganisms have revealed the existence and apparent abundance of novel eukaryotic lineages, opening new avenues for phylogenetic, evolutionary, and ecological research. Novel marine stramenopiles, identified by 18S ribosomal DNA sequences within the basal part of the stramenopile radiation but unrelated(More)
Planktonic picoeukaryotes are important players in coastal marine food webs but little is known about their diversity. Here we report the picoeukaryotic diversity in Blanes Bay (NW Mediterranean) by retrieving environmental 18S rDNA sequences and by obtaining stable cultures. Four genetic libraries (one per season) were constructed and 383 clones analyzed,(More)
Picoplanktonic prasinophytes are well represented in culture collections and marine samples. In order to better characterize this ecologically important group, we compared the phylogenetic diversity of picoplanktonic prasinophyte strains available at the Roscoff Culture Collection (RCC) and that of nuclear SSU rDNA sequences from environmental clone(More)
Despite the fact that the smallest eukaryotes (cells less than 5 micro m in diameter) play key roles in marine food webs, particularly in open oligotrophic areas, the study of their in situ diversity started just one year ago. Perhaps the most remarkable finding of the most recent studies has been the discovery of completely new phylogenetic lineages, such(More)
The marine dinoflagellates commonly responsible for toxic red tides are parasitized by other dinoflagellate species. Using culture-independent environmental ribosomal RNA sequences and fluorescence markers, we identified host-specific infections among several species. Each parasitoid produces 60 to 400 offspring, leading to extraordinarily rapid control of(More)
The objectives of this study were 1) to study the genetic diversity of the Alexandrium, Dinophysis and Karenia genera along the French coasts in order to design probes targeting specific DNA regions, and 2) to apply PCR-based detection to detect these three toxic dinoflagellate genera in natural samples. Genetic diversity of these toxic taxa was first(More)
The importance of the cyanobacteria Prochlorococcus and Synechococcus in marine ecosystems in terms of abundance and primary production can be partially explained by ecotypic differentiation. Despite the dominance of eukaryotes within photosynthetic picoplankton in many areas a similar differentiation has never been evidenced for these organisms. Here we(More)
The genetic diversity of picoplanktonic (i.e. cells that can pass through a 3 mum pore-size filter) green algae was investigated in the Mediterranean Sea in late summer by a culture-independent approach. Genetic libraries of the 18S rRNA gene were constructed using two different primer sets. The first set is commonly used to amplify the majority of(More)
BACKGROUND The deep sea floor is considered one of the most diverse ecosystems on Earth. Recent environmental DNA surveys based on clone libraries of rRNA genes confirm this observation and reveal a high diversity of eukaryotes present in deep-sea sediment samples. However, environmental clone-library surveys yield only a modest number of sequences with(More)