3,234 research outputs found
Photobiont 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
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
Ein Beitrag zur Geschichte der Biologie an der Georgia Augusta Göttingen
No full textSoftcover, 17x24Der aus Westfalen stammende Gottfried Dietrich Wilhelm Berthold (1854-1937) ist als Botaniker des 19. und beginnenden 20. Jahrhunderts eng mit der Geschichte der Georgia Augusta in Göttingen verwoben. Er hatte sich bereits als Student an der Universität Göttingen mit Algen beschäftigt und seine Dissertation dieser Thematik gewidmet. Nach Forschungsaufenthalten an der Zoologischen Station in Neapel, wo er intensiv Untersuchungen an Algen durchführte, habilitierte er sich 1881 in Göttingen bei Johannes Reinke. Später übernahm er dessen Professur für Botanik sowie dessen Direktorat am Pflanzenphysiologischen Institut und widmete sich entwicklungsmechanischen bzw. physiologischen Fragen bei höheren Pflanzen. Die vorliegende Monografie untersucht erstmalig anhand der gegenwärtigen Forschungslage Leben und Wirken Bertholds. Bertholds Lebensgeschichte wird chronologisch und in größtmöglicher Vollständigkeit dargestellt. Bildungsgeschichtliche Akzente, der personelle Konnex zu Johannes Reinke und der Einfluss der Zoologischen Station Neapel finden hier ebenso Platz wie die Rekonstruktion der Lehr- und Forschungstätigkeiten und der familiären Verhältnisse. Da Berthold vorrangig als Phykologe, also Algenkundler anzusehen ist, widmet sich der zweite Teil dem Forschungsschwerpunkt Algen. Dabei werden vor allem die meeresbiologischen Aspekte seiner Forschung am Golf von Neapel untersucht. Bertholds unterschiedliche Lebensstationen können in Zusammenhang mit seinen Publikationen betrachtet werden, dieser Teil untersucht daher das wissenschaftliche Wirken Bertholds. Anhand der aktuellen Quellenlage wird der Bestand seiner Werke aufgearbeitet und katalogisiert. Die vollständige Bibliografie ermöglicht die Bestimmung von Schwerpunkten in Bertholds wissenschaftlichen Untersuchungen. So bietet diese erste Monografie über Gottfried D. W. Berthold ein Fundament für die Beurteilung seines OEuvres und seiner Wirkung auf die Phykologie bzw. die Botanik. Sie ist eine angemessene Erinnerung an ihn und ermöglicht eine gebührende Würdigung seines Wirkens. Die vorliegende Studie ist ein Beitrag zur Universitäts- und Wissenschaftsgeschichte der Georgia Augusta.Gottfried Dietrich Wilhelm Berthold (1854-1937) was one the foremost botanists and phycologists at the end of the 19th century. Born and educated in Westphalia, he enrolled at the Georgia Augusta to study plant sciences and focused on algae. After research stays at the Zoological Station at Naples he succeeded his mentor Johannes Reinke on his chair at the Institute of Plant Physiology at the Georgia Augusta Göttingen until 1923. In this study we focus on the biography of Berthold, his private and scientific life, interaction with J. Reinke and other topics related to the life of Berthold. In a second part we highlight his research on algae at the Gulf of Naples. We conclude with an evaluation of his scientific work in the light of the different phases in his life including a full bibliography of his scientific publications. Our study contributes to history of science at the Georgia Augusta
Phylogenetic relationships of the Physciaceae inferred from rDNA sequence data and selected phenotypic characters
No full textThe monophyletic origin of the ascomycete family Physciaceae, its position within the Lecanorales and the phylogenetic structure within the family were investigated using nuclear rDNA sequence analyses. The common origin of the Caliciaceae and Physciaceae as previously shown (Wedin et al 2000) was confirmed. Further it could be shown that the Caliciaceae are nested within the Physciaceae. A unique region in loop 37 of the SSU rRNA secondary structure model was identified, which characterizes the Physciaceae/Caliciaceae. The SSU rDNA sequence data did not support a particular relationship with any other Lecanoralean family. Analyses of ITS rDNA sequences revealed a bifurcation of the Physciaceae/Caliciaceae clade, which was found to be congruent with the distribution of certain morphological characters. The congruence with the ITS phylogeny demonstrated the phylogenetic significance of ascus type, hypothecium pigmentation, ascospore characters and excipulum type. Fine-structure details of ascospores and the structure of excipula were found to be important in the recognition of convergences in these traits. Other previously used characters, i.e., growth habit, certain ascospore types or structure of the upper cortex, were found to be of multiple origins within the Physciaceae. All monophyletic lineages of noncrustose growth habit exhibit uniform ascospore types, indicating a higher evolutionary age of ascospore types than foliose growth habit. The taxonomic segregation of the Physciaceae into the Physciaceae and Caliciaceae is proposed here
Chroococcidiopsis and Heterocyst-Differentiating Cyanobacteria Are Each Other's Closest Living Relatives
No full textMany filamentous cyanobacteria reduce atmospheric nitrogen in specialized differentiated cells called heterocysts. Here we present evidence that shows that members of the unicellular non-heterocyst-differentiating genus Chroococcidiopsis and the filamentous heterocyst-differentiating cyanobacteria are each other's closest living relatives. Distance, maximum-parsimony, and maximum-likelihood analyses of complete small subunit ribosomal RNA gene sequences yielded highly congruent support for the monophyly of Chroococcidiopsis and the heterocyst-differentiating cyanobacteria. Our results demonstrate that the order Pleurocapsales, which traditionally contains Chroococcidiopsis, is a polyphyletic assemblage with the ability to reproduce by multiple fission having arisen independently at least twice during the cyanobacterial radiation. Our data also reject Myxosarcina as a sister taxon to Chroococcidiopsis, indicating that the numerous presumed shared derived characters thought to unite the two genera evolved independently. The sequence divergence within the Chroococcidiopsis lineage is comparable to and probably exceeds that in the entire heterocyst-differentiating lineage. Chroococcidiopsis forms unique survival cells under nitrogen-limiting conditions, and the sister group relationship with the heterocystous cyanobacteria shown here suggests that differentiation of these cells and heterocysts may be related processes. (C) 2002 Elsevier Science (USA)
CHANGES IN SOIL ALGAL COMMUNITIES WITH LAND USE AND MANAGEMENT INTENSITY: A CULTURAL APPROACH
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