1,721,141 research outputs found
The Culture Collection of Algae at Göttingen University (SAG): A Biological Resource for Biotechnological and Biodiversity Research
No full textAbstractThe SAG is one of the most comprehensive resources of microalgal cultures (www.epsag.uni-goettingen.de). It is supporting research in biotechnology and biodiversity through ex situ conservation of algae and expert knowledge on identifying and isolating. Multiple strains proven to represent the same microalgal species exhibit extensive genotypic diversity interesting for further exploitation. Cryopreservation is well suited to circumvent problems associated with perpetual maintenance, but needs optimization to ensure genetic stability. To ensure the SAG's reliability, primary goals are correctly identified strains as references for DNA sequence comparisons. Novel isolates from unusual terrestrial habitats worth further biotechnological exploitation are being developed
Phylogenetic relationships of green algae assigned to the genus Planophila (Chlorophyta): evidence from 18S rDNA sequence data and ultrastructure
No full textPhylogenetic analyses, based upon nuclear small-subunit ribosomal RNA gene sequences, of four 'chlorosarcinoid' species referred to Planophila Gerneck show that the genus is polyphyletic. The type species, P. laetevirens Gerneck, is closely related to species in the Ulotrichales, Ulvophyceae. The monotypic sarcinoid genus Pseudendocloniopsis is the closest relative of Planophila; the two genera represent the addition of a new morphological type to the Ulotrichales. Planophila microcystis (Dangeard) Kornmann & Sahling forms a clade at the base of the Ulvophyceae with Oltmannsiellopsis, and thus belongs to the Oltmannsiellopsidales. This result is also supported by the Oltmannsiellopsis-like ultrastructure of P. microcystis zoospores. Planophila sp. B from Antarctica, which has Trehouxia-like pyrenoid structure, is a trebouxiophyte closely related to Chlorella-like unicellular coccoids, Stichococcus bacillaris and Prasiola species. This is the first robustly supported molecular phylogenetic analysis that places Prasiola in the Trebouxiophyceae. As shown previously, P. terrestris Groover & Hofstetter belongs to the Chaetopeltidales, Chlorophyceae. Dangemannia gen. nov. (type species: D. microcystis (Dangeard) comb. nov.), Floydiella gen. nov. (type species: F. terrestris (Groover & Hofstetter) comb. nov.) and Pabia gen. nov. (type: P. signiensis sp. nov.) are proposed
CHANGES IN SOIL ALGAL COMMUNITIES WITH LAND USE AND MANAGEMENT INTENSITY: A CULTURAL APPROACH
No full textPhotobiont selectivity in the epiphytic lichens Hypogymnia physodes and Lecanora conizaeoides
No full textIn two lichen species, Hypogymnia physodes and Lecanora conizaeoides, often used as model organisms for pollution-sensitive and pollution-tolerant epiphytic lichens, respectively, the hypothesis was tested that the toxitolerance of the Trebouxia photobiont limits the tolerance of the entire lichen symbiosis. Being lecanoralean-trebouxioid associations, H. physodes and L. conizaeoides represent the most common type of lichens. Photobionts of both lichen species deriving from microhabitats with varying supply of S and heavy metals were identified using nuclear ITS nrDNA sequencing. The photobiont of L. conizaeoides was identified as T. simplex, whereas the photobiont of H. physodes belongs to an undescribed Trebouxia species, related to T. jamesii subsp. angustilobata and provisionally named as T. hypogymniae Hauck & Friedl ined. Since T. hypogymniae ined. is also known from Lecidea silacea, which is characteristic of rock and slag with high heavy metal content, a high sensitivity of this alga to pollutants is unlikely to be a key factor for the relatively low toxitolerance of H. physodes. Furthermore, the photobiont cannot be crucial for the extremely high toxitolerance of L. conizaeoides, as T simplex is also known from pollution-sensitive lichens of the fruticose genus Pseudevernia. These findings suggest that the photobiont is not generally a key factor determining pollution sensitivity in the most common type of lichen symbiosis. The high specificity for T. simplex in L. conizaeoides in existing populations of L. conizaeoides suggest that already established thalli could be a source of photobiont cells for re-lichenization
Vertical evolution and intragenic spread of lichen-fungal group I introns
No full textOne family within the Euascomycetes (Ascomycota), the lichen-forming Physciaceae, is particularly rich in nuclear ribosomal [r]DNA group I introns. We used phylogenetic analyses of group I introns and lichen-fungal host cells to address four questions about group I intron evolution in lichens, and generally in all eukaryotes: 1) Is intron spread in the lichens associated with the intimate association of the fungal and photosynthetic cells that make Lip the lichen thallus? 2) Are the Multiple group I introns in the lichen-fungi of independent origins, or have existing introns spread into novel sites in the rDNA? 3) If introns have moved to novel sites, then does the exon context of these sites provide insights into the mechanism of intron spread? and 4) What is the pattern of intron loss in the small subunit rDNA gene of lichen-fungi? Our analyses show that group I introns in the lichen-fungi and in the lichen-algae (and lichenized cyanobacteria) do not share a close evolutionary relationship, suggesting that these introns do not move between the symbionts. Many group I introns appear to have originated in the common ancestor of the Lecanorales, whereas others have spread within this lineage (particularly in the Physciaceae) putatively through reverse-splicing into novel rRNA sites. We suggest that the evolutionary history of most lichen-fungal group I introns is characterized by rare gains followed by extensive losses in descendants, resulting in a sporadic intron distribution. Detailed phylogenetic analyses of the introns and host cells are required, therefore, to distinguish this scenario from the alternative hypothesis of widespread and independent intron gains in the different lichen-fungal lineages
CHANGES IN SOIL ALGAL COMMUNITIES WITH LAND USE AND MANAGEMENT INTENSITY: A CULTURAL APPROACH
No full textIdentification of photobionts from the lichen family Physciaceae using algal-specific ITS rDNA sequencing
No full textThe identity of photobionts from 20 species of the Physciaceae from different habitats and geographical regions has been determined by ITS rDNA sequence comparisons in order to estimate the diversity of photobionts within that lichen group, to detect patterns of specificity of mycobionts towards their photobionts and as a part of an ongoing study to investigate possible parallel cladogenesis of both symbionts. Algal-specific PCR primers have been used to determine the ITS rDNA sequences from DNA extractions of dried lichens that were up to 5 years old. Direct comparisons and phylogenetic analyses allowed the assignment of Physciaceae photobionts to four distinct clades in the photobiont ITS rDNA phylogeny. The results indicate a diversity within the genus Trebouxia Puymaly and Physciaceae photobionts that is higher than expected on the basis of morphology alone. Physciaceae photobionts belonged to 12 different ITS lineages of which nine could unambiguously be assigned to six morphospecies of Trebouxia. The identity of the remaining three sequences was not clarified; they may represent new species. Specificity at the generic level was low as a whole range of photobiont species were found within a genus of Physciaceae and different ranges were detected. The photobionts of Physcia (Schreb.) Michaux were closely related and represented one morphospecies of Trebouxia, whereas the algal partners of Buellia De Not and Rinodina (Ach.) S. Gray were in distant lineages of the ITS phylogeny and from several Trebouxia morphospecies. Photobiont variation within a genus of Physciaceae may be due to phylogeny, geographical distance or because photobionts from neighbouring lichens were taken ('algal sharing'). At the species level Physciaceae mycobionts seem to be rather selective and contained photobionts that were very closely related within one morphospecies of Trebouxia. (C) 2001 The British Lichen Society
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