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Victor Smetacek
Terrestrial ecologists and biogeochemists are in direct contact with their objects of study via sense organs evolved in those environments; they hence share a common awareness because they can all see the whole elephant, as in the ancient Indian parable. Pelagic ecologists and biogeochemists on the other hand are the blind men groping different parts of the elephant - the protist-dominated biome of the planet - in attempts to understand its structure and functioning in terms of organism life cycles and the biogenic elements of which they are made...
August 27, 2018: Protist
Gabriel A Schuler, Alexander K Tice, Rebecca A Pearce, Emily Foreman, Jared Stone, Sarah Gammill, John D Willson, Chris Reading, Jeffrey D Silberman, Matthew W Brown
Sainouroidea is a molecularly diverse clade of cercozoan flagellates and amoebae in the eukaryotic supergroup Rhizaria. Previous 18S rDNA environmental sequencing of globally collected fecal and soil samples revealed great diversity and high sequence divergence in the Sainouroidea. However, a very limited amount of this diversity has been observed or described. The two described genera of amoebae in this clade are Guttulinopsis, which displays aggregative multicellularity, and Rosculus, which does not. Although the identity of Guttulinopsis is straightforward due to the multicellular fruiting bodies they form, the same is not true for Rosculus, and the actual identity of the original isolate is unclear...
August 22, 2018: Protist
Scott R Santos, Mary Alice Coffroth
No abstract text is available yet for this article.
November 2018: Protist
Sebastian C Treitli, Michael Kotyk, Naoji Yubuki, Eliška Jirounková, Jitka Vlasáková, Pavla Smejkalová, Petr Šípek, Ivan Čepička, Vladimír Hampl
Oxymonads are a group of flagellates living as gut symbionts of insects or vertebrates. They have several unique features, one of them being the absence of mitochondria. Diversity of this group is seriously understudied, which is particularly true for small species from the family Polymastigidae. We isolated 34 strains of oxymonads with Polymastigidae-like morphology from 24 host species and unused cesspits and sequenced the SSU rRNA gene. Our strains formed two clades in the phylogenetic tree with Streblomastix strix branching between them...
November 2018: Protist
Timur G Simdyanov, Gita G Paskerova, Andrea Valigurová, Andrei Diakin, Magdaléna Kováčiková, Joseph Schrével, Laure Guillou, Andrej A Dobrovolskij, Vladimir V Aleoshin
Blastogregarines are poorly studied parasites of polychaetes superficially resembling gregarines, but lacking syzygy and gametocyst stages in the life cycle. Furthermore, their permanent multinuclearity and gametogenesis by means of budding considerably distinguish them from other parasitic Apicomplexa such as coccidians and hematozoans. The affiliation of blastogregarines has been uncertain: different authors considered them highly modified gregarines, an intermediate apicomplexan lineage between gregarines and coccidians, or an isolated group of eukaryotes altogether...
November 2018: Protist
Yegor Shɨshkin, Daria Drachko, Vladimir I Klimov, Vasily V Zlatogursky
Two closely related new species of centrohelid heliozoans with unusual morphology were studied with light and electron microscopy. Sequences of the 18S rRNA gene were also obtained and secondary structure of 18S rRNA molecule reconstructed. The cells, covered with inner siliceous plate scales formed colonies. The entire colony was surrounded with a thick layer of external scales. Inner scales were tabulate and had a patternless surface, except for the presence of an axial rib. Outer scales had a boat-like (Yogsothoth knorrus gen...
November 2018: Protist
Kerstin Hoef-Emden
For years the genus Chroomonas was defined as being a cryptophyte with rectangular periplast plates, with a gullet and with biliprotein types PC 630 or 645. In phylogenetic trees the genus proved to be paraphyletic. Moreover, cells with hexagonal periplast plates were found in an SEM preparation from material of the type species C. nordstedtii. In this study, material of Hansgirg's C. nordstedtii was subjected to PCR and to sequencing of two short DNA tags. These tags allowed for an unambiguous identification of the real C...
November 2018: Protist
Izumi Iwata, Daiske Honda
Thraustochytrid cells attach to their food via ectoplasmic nets (ENs). Here, we analyzed the cause and effect relationship between the various forms and functions of ENs of Schizochytrium aggregatum. The ENs spread out over a large area forming a fine network to efficiently search for the experimental food source. After recognizing the experimental food source, the ENs that attached to the food source became thicker, and net elements developed. The thick ENs on the surface at the attachment site were enveloped in dense materials (fibrous materials), which were visualized as fibrous layers under a transmission electron microscope...
November 2018: Protist
Alexis D Fischer, Michael L Brosnahan, Donald M Anderson
Many dinoflagellate cysts experience dormancy, a reversible state that prevents germination during unfavorable periods. Several of these species also cause harmful algal blooms (HABs), so a quantitative understanding of dormancy cycling is desired for better prediction and mitigation of bloom impacts. This study examines the effect of cold exposure on the duration of dormancy in Alexandrium catenella, a HAB dinoflagellate that causes paralytic shellfish poisoning (PSP). Mature, dormant cysts from Nauset Marsh (Cape Cod, MA USA) were stored at low but above freezing temperatures for up to six months...
November 2018: Protist
Pooja Potdar, Patricia Pinto, Nicole D'Souza, Prajakta Joshi, Akshay Malwade, Subhojit Sen
To circumvent nuclei isolation for nucleosomal mapping of wild-type (cell walled) algal cells, we developed a quick and versatile methodology, by abrasion of whole cells (Chlamydomonas, Scenedesmus and yeast), allowing Micrococcal Nuclease (MNase) direct access to nuclear chromatin, in situ. Varying parameters such as bead abrasion, vortex and incubation conditions, we optimized capture of an 'early digest' which may probe chromatin differentially, based on nucleosome accessibility. A comparison of such ladders across vegetative cells, gametes and zygotes revealed an increase in the average nucleosomal repeat length (+17-34nt) upon gametogenesis, indicating a trend of chromatin compaction...
November 2018: Protist
Zuo Yi Chen, Nina Lundholm, Øjvind Moestrup, Janina Kownacka, Yang Li
To understand the diversity of the diatom genus Chaetoceros Ehrenberg, the C. lorenzianus complex was previously chosen as a model and three new species were described. In the present study, yet another new species, Chaetoceros pauciramosus sp. nov., was discovered from Chinese tropical waters and the temperate south-eastern Baltic Sea. In the latter locality it has been known since 2003 and identified as C. cf lorenzianus, and now found to comprise a dominating component of the autumn phytoplankton community...
November 2018: Protist
Olga Matantseva, Ilya Pozdnyakov, Maren Voss, Iris Liskow, Sergei Skarlato
The spread of harmful dinoflagellate blooms has been linked to the increasing availability of nitrogen, including its dissolved organic forms. The relationships between organic and inorganic nutrient uptake by dinoflagellates are not completely understood; moreover, it is not clear whether organic substances are used exclusively as nitrogen or also as carbon sources. We used laboratory culture experiments to investigate the concurrent uptake of glycine and nitrate by Prorocentrum minimum and estimate a role of two widespread organic substrates, glycine and urea, as carbon sources...
November 2018: Protist
Thomas A Frankovich, Matt P Ashworth, Michael J Sullivan, Edward C Theriot, Nicole I Stacy
Until now only one group of diatoms, the Bacillariaceae, was known to contain heterotrophic representatives. We show that a second group, represented by species in the genus Tursiocola, has undergone evolutionary loss of photosynthesis within the Bacillariophyta. Heterotrophy was evidenced by the presence of only apochlorotic cells in live and motile specimens. Three species of Tursiocola (T. bondei sp. nov., T. alata sp. nov., and T. gracilis sp. nov.), of which at least two are apochlorotic, are described as new to science from the skin of Florida manatees...
August 2018: Protist
Irena Kaczmarska, James M Ehrman, Nickolai A Davidovich, Olga I Davidovich, Yulia A Podunay
Reproductive development in Ardissonea crystallina revealed a unique mode of enlargement involving a combination of novel and known structures. In light microscopy, auxospores of this elongated polar centric diatom were superficially similar to the auxospores of pennates. With SEM we found three different components in the auxospore wall. In the youngest, nearly spherical cell-stage, the wall consisted only of a delicate veil containing minute siliceous spherules. Incunabular elements developed underneath this layer...
August 2018: Protist
Konstanze Kobel-Höller, Kevin Gley, Janina Jochinke, Kristina Heider, Verena Nadin Fritsch, Ha Viet Duc Nguyen, Timo Lischke, Renate Radek, Ria Baumgrass, Rupert Mutzel, Sascha Thewes
Calcineurin is involved in development and cell differentiation of the social amoeba Dictyostelium discoideum. However, since knockouts of the calcineurin-encoding genes are not possible in D. discoideum it is assumed that the phosphatase also plays a crucial role during vegetative growth of the amoebae. Therefore, we investigated the role of calcineurin during vegetative growth in D. discoideum. RNAi-silenced calcineurin mutants showed cellular alterations with an abnormal morphology of mitochondria and had increased content of mitochondrial DNA (mtDNA)...
August 2018: Protist
William Bourland, Johana Rotterová, Xiaotian Luo, Ivan Čepička
Class Armophorea Lynn, 2004 includes two orders of mainly free-living anaerobic ciliates, Armophorida Jankowski, 1980 and Metopida Jankowski, 1980 and, a third, the exclusively endosymbiotic Clevelandellida. Kahl described the majority of free-living metopid species early in the 20th century. Excepting Jankowski in the 1960's, little further interest was shown in this group. Metopus turbo Dragesco and Dragesco-Kernéis, 1986, from a West African pond, was more recently described. Although not explicitly described as endemic, Dragesco believed in some degree of endemism of sub-Saharan ciliates...
August 2018: Protist
Paul Christiaan Venter, Frank Nitsche, Anja Scherwass, Hartmut Arndt
By measuring the change in soil protist communities, the effect of human land use on grasslands can be monitored to promote sustainable ecosystem functioning. Protists form the active link in the rhizosphere between the plant roots and higher trophic organisms; however, only few morphological species and their ecological values have yet been described in this context. To investigate the communicability between morphological and molecular databases used in the molecular barcoding of protists and in the biomonitoring of grassland soil, the present high-throughput sequencing (HTS) study (N=150) covered the area of central Europe (mesoscale) known to be well studied for ciliated protists...
August 2018: Protist
Anna Ronikier, Adam T Halamski
Myxomycetes is one of the largest groups of protists belonging to Amoebozoa, with ca 1,000 species recognised and more than 4,000 names in use. Historically, myxomycetes were considered fungi or protozoans which, however, fell under the provisions of the former International Code of Botanical Nomenclature (ICBN), currently the International Code of Nomenclature for algae, fungi, and plants (ICN). Attempts to apply the International Code of Zoological Nomenclature (ICZN) to myxomycetes were rare and inconsistent; thus, we argue that Myxomycetes is not a truly ambiregnal group (i...
August 2018: Protist
Kensuke Seto, Yousuke Degawa
Chytrids are early diverging lineages of true fungi that reproduce with posteriorly uniflagellate zoospores. In aquatic ecosystems, parasitic chytrids of algae have important ecological roles by influencing the population dynamics of phytoplankton and transferring nutrients and energy from inedible algae to zooplankton via zoospores. Despite their ecological importance, information on parasitic chytrids is lacking in the current systematics of chytrids. Here, we investigated a novel chytrid culture KS100 that parasitizes the green alga, Microglena coccifera (Volvocales)...
August 2018: Protist
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