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Does climate warming stimulate or inhibit soil protist communities? A test on testate amoebae in high-arctic tundra with free-air temperature increase Universiteit Antwerpen

Andrey Tsyganov, Ivan Nijs, Lodewijk Beyens
Soil testate amoebae assemblages in a grassland area at Zackenberg (Northeast Greenland) were subjected to simulated climate-warming during the growing season using the Free-Air Temperature Increase technique. Samples were collected in upper (0 3 cm) and deeper (3 6 cm) soil horizons. Mean temperature elevations at 2.5 and 7.5 cm depth were 2.58 ± SD 1.11 and 2.13 ± SD 0.77 °C, respectively, and did not differ significantly. Soil moisture in the ...

Diversity and dynamics of protist communities in subtidal North Sea sediments in relation to metal pollution and algal bloom deposition Universiteit Gent

Annelies Pede
The Belgian Coastal Zone (BCZ) is heavily polluted by trace metals, that pose a potential threat to the marine ecosystem in the area, including to humans (a.o. via fisheries). Trace metals accumulate in silty, organically enriched sediments and changes in the environment can lead to the resuspension of the metals, with the activity of the benthic microbes as one potential factor influencing the release of TM into the water column. Benthic ...

Catalase compromises the development of the insect and mammalian stages of Trypanosoma brucei Instituut voor Tropische Geneeskunde

Eva Horakova, Drahomira Faktorova, Natalia Kraeva, Binnypreet Kaur, Jan Van Den Abbeele, Vyacheslav Yurchenko, Julius Lukes

Catalase is a widespread heme-containing enzyme, which converts hydrogen peroxide (H2O2) to water and molecular oxygen, thereby protecting cells from the toxic effects of H2O2. Trypanosoma brucei is an aerobic protist, which conspicuously lacks this potent enzyme, present in virtually all organisms exposed to oxidative stress. To uncover the reasons for its absence in T. brucei, we overexpressed different catalases in procyclic and ...

Gamete differentiation : a genetic, biochemical and evolutionary study using Ectocarpus siliculosus Universiteit Gent

Agnieszka Lipinska
Despite its prevalence among eukaryotes, there are still many questions awaiting answers and plenty of discoveries to be made with regard to the mechanisms and maintenance of sexual reproduction. Brown algae (Phaeophyceae) represent a very interesting group to study the evolution of sexual reproduction, owing to the rich variation of life cycles, fertilization modes and sex determination systems displayed by this lineage. Particularly unique are ...

Molecular evidence for distinct Antarctic lineages in the cosmopolitan terrestrial diatoms **Pinnularia borealis** and **Hantzschia amphioxys** Universiteit Antwerpen Plantentuin Meise / Agentschap Plantentuin Meise Universiteit Gent

Caroline Souffreau, Pieter Vanormelingen, Bart Van de Vijver, Tsvetelina Isheva, Elie Verleyen, Koen Sabbe, Wim Vyverman
Recent morphology-based studies indicate that freshwater diatom floras in the Antarctic comprise a significant share of endemics among a majority of apparently cosmopolitan species. Given the widespread (pseudo)cryptic species diversity in diatoms, we assessed the molecular divergence and temperature-dependent growth characteristics between Antarctic and non-Antarctic strains for two presumed species with a cosmopolitan distribution, namely ...

Uncovering the genetic basis for early isogamete differentiation : a case study of Ectocarpus siliculosus Universiteit Gent

Agnieszka Lipinska, Sofie D'Hondt, Els Van Damme, Olivier De Clerck
Background: The phenomenon of sexual reproduction characterizes nearly all eukaryotes, with anisogamy being the most prevalent form of gamete discrimination. Since dimorphic gametes most likely descend from equal-sized specialized germ cells, identifying the genetic bases of the early functional diversification in isogametes can provide better understanding of the evolution of sexual dimorphism. However, despite the potential importance to the ...

An inordinate fondness?: the number, distributions, and origins of diatom species Universiteit Gent

David G Mann, Pieter Vanormelingen
The number of extant species of diatoms is estimated here to be at least 30,000 and probably ca. 100,000, by extrapolation from an eclectic sample of genera and species complexes. Available data, although few, indicate that the pseudocryptic species being discovered in many genera are not functionally equivalent. Molecular sequence data show that some diatom species are ubiquitously dispersed. A good case can be made that at least some diatom ...

**Sphagnum**-dwelling testate amoebae in subarctic bogs are more sensitive to soil warming in the growing season than in winter Universiteit Antwerpen

Andrey Tsyganov, Rien Aerts, Ivan Nijs, Johannes H.C. Cornelissen, Lodewijk Beyens
Sphagnum-dwelling testate amoebae are widely used in paleoclimate reconstructions as a proxy for climate-induced changes in bogs. However, the sensitivity of proxies to seasonal climate components is an important issue when interpreting proxy records. Here, we studied the effects of summer warming, winter snow addition solely and winter snow addition together with spring warming on testate amoeba assemblages after eight years of experimental ...