Testate Amoeba (Arcellinida,Euglyphida) Ecology along a Poor‐Rich Gradient in Fens of Western Poland

We investigated the relationships between testate amoebae (Arcellinida, Euglyphida), vegetation and water chemistry along environmental gradients in minerotrophic peatlands (fens) in western Poland. We hypothesized that: a) hydrochemistry significantly influences structure of testate amoeba communities, and b) testate amoeba communities are more closely correlated with the hydrochemical variables (environment) than with the vegetation data. Testate amoeba communities and vegetation from 71 sample plots were investigated together with the hydro‐chemistry and hydrology based on 16 environmental variables and vegetation composition. Testate amoeba communities revealed a distinctive poor‐rich gradient in analysed fens. Mineral‐rich habitats, which were dominated by brown mosses, were preferred by a higher number of taxa than acidic habitats, which were dominated by Sphagnum. We recorded a total of 107 testate amoebae taxa. The average species richness of testate amoebae for brown mosses was higher (20) than for Sphagnum (13). We found that testate amoebae communities were similarly correlated with vascular plants, mosses and environmental parameters. Results of direct ordination demonstrate that hydrology, pH, Mg²⁺ and sodium remain the most important environmental control for the entire data set. CCA showed that in case of brown mosses hydrology, sodium and oxygen affect testate amoeba communities significantly whereas in Sphagnum only sodium emerge as most significant determining testate amoeba assemblages. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Gas Vacuoles and Flotation in the Testate Amoeba Arcella discoides

The natural formation of gas vacuoles as a method of movement is described for the testate amoeba Arcella discoides. These vacuoles are used to float the organism from the substrate to the surface in an inverted position.     

Fine-Scale Horizontal and Vertical Micro-distribution Patterns of Testate Amoebae Along a Narrow Fen/Bog Gradient

The ecology of peatland testate amoebae is well studied along broad gradient from very wet (pool) to dry (hummock) micro-sites where testate amoebae are often found to respond primarily to the depth to water table (DWT). Much less is known on their responses to finer-scale gradients, and nothing is known of their possible response to phenolic compounds, which play a key role in carbon storage in peatlands. We studied the vertical (0–3, 3–6, and 6–9 cm sampling depths) micro-distribution patterns of testate amoebae in the same microhabitat (Sphagnum fallax lawn) along a narrow ecological gradient between a poor fen with an almost flat and homogeneous Sphagnum carpet (fen) and a “young bog” (bog) with more marked micro-topography and mosaic of poor fen and bog vegetation. We analyzed the relationships between the testate amoeba data and three sets of variables (1) “chemical” (pH, Eh potential, and conductivity), (2) “physical” (water temperature, altitude, i.e., Sphagnum mat micro-topography, and DWT), and (3) phenolic compounds in/from Sphagnum (water-soluble and primarily bound phenolics) as well as the habitat (fen/bog) and the sampling depth. Testate amoeba Shannon H′ diversity, equitability J of communities, and total density peaked in lower parts of Sphagnum, but the patterns differed between the fen and bog micro-sites. Redundancy analyses revealed that testate amoeba communities differed significantly in relation to Eh, conductivity, water temperature, altitude, water-soluble phenolics, habitat, and sampling depth, but not to DWT, pH, or primarily bound phenolics. The sensitivity of testate amoebae to weak environmental gradients makes them particularly good integrators of micro-environmental variations and has implications for their use in paleoecology and environmental monitoring. The correlation between testate amoeba communities and the concentration of water-soluble phenolic suggests direct (e.g., physiological) and/or indirect (e.g., through impact on prey organisms) effects on testate amoebae, which requires further research.     

Vernalophrys algivore gen. nov., sp. nov. (Rhizaria: Cercozoa: Vampyrellida), a New Algal Predator Isolated from Outdoor Mass Culture of Scenedesmus dimorphus

Microbial contamination is the main cause of loss of biomass yield in microalgal cultures, especially under outdoor environmental conditions. Little is known about the identities of microbial contaminants in outdoor mass algal cultures. In this study, a new genus and species of vampyrellid amoeba, Vernalophrys algivore, is described from cultures of Scenedesmus dimorphus in open raceway ponds and outdoor flat-panel photobioreactors. This vampyrellid amoeba was a significant grazer of Scenedesmus and was frequently associated with a very rapid decline in algal numbers. We report on the morphology, subcellular structure, feeding behavior, molecular phylogeny, and life cycle. The new amoeba resembles Leptophrys in the shape of trophozoites and pseudopodia and in the mechanism of feeding (mainly by engulfment). It possesses two distinctive regions in helix E10_1 (nucleotides 117 to 119, CAA) and E23_1 (nucleotides 522 and 523, AG) of the 18S rRNA gene. It did not form a monophyletic group with Leptophrys in molecular phylogenetic trees. We establish a new genus, Vernalophrys, with the type species Vernalophrys algivore. The occurrence, impact of the amoeba on mass culture of S. dimorphus, and means to reduce vampyrellid amoeba contamination in Scenedesmus cultures are addressed. The information obtained from this study will be useful for developing an early warning system and control measures for preventing or treating this contaminant in microalgal mass cultures.     

Description of the marine predator Sericomyxa perlucida gen. et sp. nov., a cultivated representative of the deepest branching lineage of vampyrellid amoebae (Vampyrellida,Rhizaria)

The vampyrellids (Vampyrellida, Rhizaria) are naked amoebae of considerable genetic diversity. Three families have been well-defined (Vampyrellidae, Leptophryidae, and Placopodidae), but most vampyrellid lineages detected by environmental sequencing are poorly known or completely uncharacterized. In the brackish sediment of Lake Bras D’Or, Nova Scotia, Canada, we discovered an amoeba with a vampyrellid-like life history that was morphologically dissimilar from previously known vampyrellid taxa. We established a culture of this amoeba, studied its feeding behavior and prey range specificity, and characterized it with molecular phylogenetic methods and light and electron microscopy. The amoeba was a generalist predator (i.e. eukaryotroph), devouring a range of marine microalgae, with a strong affinity for some benthic diatoms and Chroomonas. Interestingly, the amoeba varied its feeding strategy depending on the prey species. Small diatoms were engulfed whole, while larger species were fed on through extraction with an invading pseudopodium. The SSU rRNA gene phylogenies robustly placed the amoeba in the most basal, poorly described lineage (“clade C”) of the Vampyrellida. Based on the phylogenetic position and the distinct morphology of the studied amoeba, we here describe it as Sericomyxa perlucida gen. et sp. nov., and establish the new vampyrellid family Sericomyxidae for “clade C.”     

Transfer of the Thecate Amoeba Lecythium mutabilis to a Novel Genus Omnivora (Fiscullidae,Thecofilosea, Cercozoa)

Thecofilosea is a class in Cercozoa (Rhizaria) comprising mainly freshwater‐inhabiting algivores. Recently, numerous isolates of thecofilosean amoebae have been cultured and were characterized by an integrated morphological and molecular approach. As attempts to establish a culture of Lecythium mutabilis repeatedly failed, it was not yet investigated by molecular means. We isolated single cells of L. mutabilis directly from their habitat and successfully sequenced the V4 region of their SSU rDNA. Phylogenetic analyses showed that L. mutabilis is not directly related to the genus Lecythium and instead branches within the Fiscullidae (Tectofilosida, Thecofilosea). Accordingly, we transfer the species L. mutabilis to a novel genus Omnivora gen. nov.     

Pathogenicity, Morphology, and Differentiation of Acanthamoeba

Acanthamoeba keratitis is sight threatening corneal infection caused by pathogenic Acanthamoeba. Previous studies have shown the genotypic differences between pathogenic and non-pathogenic species/strains of Acanthamoeba. In this study, we examined the morphological differences between pathogenic and non-pathogenic species/strains using scanning electron microscopy. Pathogenic Acanthamoeba exhibited higher number of acanthopodia (structures associated with the binding of amoeba to the target cells) as compared to non-pathogens. In addition, interactions of amoeba with the corneal epithelial cells were studied. Only pathogenic amoeba exhibited adhesion to epithelial cells. Further results indicated that phagocytosis occurs in the pathogenic amoeba by the formation of amoebastome (characteristic of amoeba phagocyte). This study showed that Acanthamoeba phagocytosis may be both an efficient means of obtaining nutrients for the amoeba and a significant factor in the pathogenesis of Acanthamoeba infections. Received: 2 April 2001 / Accepted: 12 April 2001     

Primary and Secondary Structure of the Small-Subunit Ribosomal RNA of the Naked, Marine Amoeba Vannella anglica: Phylogenetic Implications

The primary and secondary structure of the small-subunit ribosomal RNA (ssrRNA) gene from the naked, marine amoeba, Vannella anglica (subclass Gymnamoebia), was determined. The ssrRNA is 1962 nucleotides in length, with a low G+C content of 37.1%. The ssrRNA is composed of several uncommon secondary structure features including helix E8-1, which may be a useful target for rRNA probes for the direct identification of isolates in mixed culture. Phylogenetic analysis of sequence data showed that V. anglica branched prior to the rapid diversification of the eukaryotes. It did not associate with the other naked, lobose amoebae represented by Acanthamoeba and Hartmannella, indicating that Vannella represents a separate amoeboid lineage and the subclass Gymnamoebia is polyphyletic. Received: 9 July 1998 / Accepted: 16 November 1998     

Trophic coupling of a testate amoeba and <Emphasis Type="Italic">Microcystis</Emphasis> species in a hypertrophic pond

Seasonal changes in abundance of the testate amoeba Penardochlamys sp. and its food vacuole contents were investigated in relation to blooms of the cyanobacteria Microcystis spp. in a hypertrophic pond from April 1999 to March 2000. The behavior of the amoeba feeding on M. aeruginosa and M. wesenbergii was also observed in the laboratory. The amoeba was detectable from late May to November 1999 during the blooms of Microcystis spp. Cell densities of the amoeba fluctuated between 1.4 and 350 cells ml^–1 with some sporadic peaks, which did not coincide with rapid decreases in the abundance of Microcystis spp. Food vacuoles contained only Microcystis cells; other prey items were not found, suggesting that this amoeba utilized only the cyanobacteria as food. The amoeba was frequently found attached to Microcystis colonies, but was not associated with other suspended particles. Observation of the amoeba feeding revealed the feeding mechanism and that the amoeba was able to graze on both species of Microcystis. These results suggest that the trophic coupling of these organisms is substantial, although grazing by the amoeba is not sufficient to regulate the dynamics of Microcystis populations in this hypertrophic pond.     

Ciliates from Antarctic sea ice

Five ciliates, Chlamydonella prostomata nov. sp., Paractedoctema acruosa nov. gen., nov. sp., Urocyclon ovatum nov. gen., nov. sp., Porpostoma grassei (Corliss and Snyder 1986) and Cytharoides balechi Tuffrau 1974, collected from sea ice in the Weddell Sea, Antarctica were morphologically and taxonomically investigated. The new genus Paractedoctema is characterized as: Cyclidiidae with naked snout-like apical end and three well-developed membranelles which are multi-rowed in structure and closely apposed one to another; paroral membrane extending anteriorly to about mid-level of M1; one caudal cilium; and silverline system Cyclidium-like. Since Urocyclon Small and Lynn 1985 is a nomen nudum because no type species has been fixed, we re-establish the genus and give a revised definition: uronematids mostly with inverted pear-shaped body and subequatorially positioned cytostome; apical plate dominant; membranelle 1 highly reduced; and paroral membrane extending anteriorly to about mid-level of membrane 2. Based on this new definition, a new combination is suggested: Homalogastra cymruensis (Pérez-Uz and Hope 1997) comb. nov. (formerly Urocyclon cymruensis Pérez-Uz and Hope 1997). For the well-known genus Chlamydonella, an improved diagnosis has been given according to our observations and the data obtained: Lynchellidae without plasmatic protrusions on ventral side; several to many somatic kineties making no noticeable naked gap between left and right areas; perioral kineties continuous or slightly fragmented with leftmost rows parallel to each other, which are arched transversely; and cytopharyngeal rods (nematodesmata) toothed. Macronucleus usually dimorphic. Regarding the related genus Lynchella Kahl 1933, we suggest that the original diagnosis by Kahl should be maintained. Thus, the genus diagnosis is re-provided: Lynchellidae with plasmatic protrusions on ventral side; several to many somatic kineties making no noticeable naked gap between left and right areas; perioral kineties continuous or fragmented with some rows parallel to each other; cytopharyngeal rods toothed; macronucleus generally dimorphic. In the light of the redefinition, a new combination has been made: Chlamydonella nordica (Jankowski 1968) comb. nov. (formerly Lynchella nordica Jankowski 1968). Accepted: 10 October 1999     

Diverse Legionella‐Like Bacteria Associated with Testate Amoebae of the Genus Arcella (Arcellinida: Amoebozoa)

Diverse species of Legionella and Legionella‐like amoebal pathogens (LLAPs) have been identified as intracellular bacteria in many amoeboid protists. There are, however, other amoeboid groups such as testate amoeba for which we know little about their potential to host such bacteria. In this study, we assessed the occurrence and diversity of Legionella spp. in cultures and environmental isolates of freshwater arcellinid testate amoebae species, Arcella hemispherica, Arcella intermedia, and Arcella vulgaris, via 16S rRNA gene sequence analyses and fluorescent in situ hybridization (FISH). Analysis of the 16S rRNA gene sequences indicated that A. hemispherica, A. intermedia, and A. vulgaris host Legionella‐like bacteria with 94–98% identity to other Legionella spp. based on NCBI BLAST search. Phylogenetic analysis placed Legionella‐like Arcella‐associated bacteria (LLAB) in three different clusters within a tree containing all other members of Legionella and LLAPs. The intracellular localization of the Legionella within Arcella hosts was confirmed using FISH with a Legionella‐specific probe. This study demonstrates that the host range of Legionella and Legionella‐like bacteria in the Amoebozoa extends beyond members of “naked” amoebae species, with members of the testate amoebae potentially serving an ecological role in the dispersal, protection, and replication of Legionella spp. in natural environments.     

Marinamoeba thermophila, a new marine heterolobosean amoeba growing at 50 °C

Two amoeba strains were isolated from marine sediment taken at the same place with 18 months interval from a region of the sea floor heated by extended submarine hot springs and fumaroles. These thermophilic amoebae grow at temperatures up to 50 °C. Sequences of the internal transcribed spacer demonstrated that the two strains belong to the same species and are different from any genus for which sequences are known. Phylogeny using small subunit ribosomal RNA places the amoeba in the Heterolobosea. Their closest relatives are the hypersaline flagellate Pleurostomum flabellatum and the hypersaline amoeba Tulamoeba peronaphora. The freshwater amoeboflagellate genera Naegleria and Willaertia belong to the same phylogenetic clade in the Vahlkampfiidae. The new marine species does not transform into flagellates. It forms cysts, which are round to ellipsoidal with few pores. Because of their unique place in the molecular phylogenetic tree, and because there is no morphologically identical species found in the literature, these isolates are considered to be a new species and a new genus, Marinamoeba thermophila.     

Structure of filose amoeba <Emphasis Type="Italic">Rhogostoma minus</Emphasis> Belar 1921 (Cryomonadida,Cercozoa) cell

The structure of the unicellular cell of filose amoeba, Rhogostoma minus Belar, 1921, is studied. Zoospores, cysts, and multinuclear plasmodia have not been found. The cell is covered by a thin shell made out of organic matter. Narrow and branched pseudopodia arise from the pseudostome. The vesicle-shaped nucleus, endoplasmic reticulum, microbodies, and Golgi apparatus are of a usual structure. The oval-shaped mitochondria carry tubular cristae. No flagellar apparatus, fibrillar structures, or extrusive organelles have been found. The amoeba feeds on bacteria. The phylogeny of R. minus in regard to other filose amoebas and flagellates is discussed.     

Testate amoeba records indicate regional 20th‐century lowering of water tables in ombrotrophic peatlands in central‐northern Alberta,Canada

Testate amoebae are abundant in the surface layers of northern peatlands. Analysis of their fossilized shell (test) assemblages allows for reconstructions of local water‐table depths (WTD). We have reconstructed WTD dynamics for five peat cores from peatlands ranging in distance from the Athabasca bituminous sands (ABS) region in western Canada. Amoeba assemblages were combined with plant macrofossil records, acid‐insoluble ash (AIA) fluxes and instrumental climate data to identify drivers for environmental change. Two functional traits of testate amoebae, mixotrophy and the tendency to integrate xenogenic mineral matter in test construction, were quantified to infer possible effects of AIA flux on testate amoeba presence. Age–depth models showed the cores each covered at least the last ~315 years, with some spanning the last millennium. Testate amoeba assemblages were likely affected by permafrost development in two of the peatlands, yet the most important shift in assemblages was detected after 1960 CE. This shift represents a significant apparent lowering of water tables in four out of five cores, with a mean drop of ~15 cm. Over the last 50 years, assemblages shifted towards more xerophilous taxa, a trend which was best explained by increasing Sphagnum s. Acutifolia and, to a lesser extent, mean summer temperature. This trend was most evident in the two cores from the sites located farthest away from the ABS region. AIA flux variations did not show a clear effect on mineral‐agglutinating taxa, nor on S. s. Acutifolia presence. We therefore suggest the drying trend was forced by the establishment of S. s. Acutifolia, driven by enhanced productivity following regional warming. Such recent apparent drying of peatlands, which may only be reconstructed by appropriate indicators combined with high chronological control, may affect vulnerability to future burning and promote emissions of CO₂.     

Effect of Lipopolysaccharide on Progesterone Production during Luteinization of Granulosa and Theca cells In Vitro

The aim of this study is to examine the effect of lipopolysaccharide (LPS) on progesterone production during luteinization of granulosa and theca cells isolated from bovine large follicles. Granulosa and theca cells isolated from large follicles of bovine ovaries were exposed to LPS under appropriate hormone conditions in vitro. Progesterone (P4) production in theca cells, but not granulosa cells, was decreased by long‐term exposure of LPS. Long‐term exposure of LPS suppressed the gene expression of luteinizing hormone receptor in theca cells. Although long‐term exposure of LPS did not affect the expression of steroidogenic acute regulatory protein (StAR) and 3β‐hydroxy‐steroid dehydrogenase (3β‐HSD) genes, it did inhibit the protein expression of StAR and 3β‐HSD in theca cells. These findings suggest that theca cells, rather than granulosa cells, are susceptible to LPS during luteinization and that LPS inhibits P4 production by decreasing protein levels of StAR during luteinization of theca cells.     

Polychaos centronucleolus n. sp. – a new terrestrial species of the genus Polychaos (Amoebozoa,Tubulinea) with nontypical nuclear structure

A new species of the “proteus-type” naked amoebae (large cells with discrete tubular pseudopodia) was isolated from tree bark sample of a birch tree in the surrounding of Kislovodsk town, Russia and named Polychaos centronucleolus n. sp. (Amoebozoa, Tubulinea). Amoebae of this species have a filamentous cell coat and a nucleus with a central compact nucleolus. This type of nucleolar organization has not been previously known for the genus Polychaos. A sequence of the 18S rRNA gene of this strain was obtained using whole genome amplification of DNA from the single amoeba cell, followed by NGS sequencing. The analysis of molecular data robustly groups this species with Polychaos annulatum within the family Hartmannellidae. Our results, together with the results of our previous studies, show that the taxonomic assignment of “proteus-type” amoebae species is becoming increasingly complex, and the taxonomic characters that can be used to classify these organisms are becoming more shadowed.     

Grellamoeba robusta gen. n., sp. n., a possible member of the family Acramoebidae Smirnov,Nassonova et Cavalier-Smith, 2008

A strain of naked amoeba isolated from pikeperch (Sander lucioperca (L.)) kidney tissue has been characterized using light- and transmission electron microscopy. Sequencing of SSU rDNA and phylogenetic analysis based on a broad dataset of sequences completed our study. All data obtained suggest that this strain belongs to a species that has not been described before. As none of the existing genera of amoebae is applicable to this organism, the new genus Grellamoeba is established and the type species Grellamoeba robusta is described. Although the phylogenetic position of the SSU rDNA sequence of the type strain of G. robusta is sensitive to the method of analysis applied, a tendency to group with Acramoeba dendroida Smirnov, Nassonova et Cavalier-Smith, 2008 is evident.     

Description of Phaeobola aeris gen. nov., sp. nov (Rhizaria,Cercozoa, Euglyphida) Sheds Light on Euglyphida’s Dark Matter

The majority of Euglyphida species are characterised by shells with imbricated silica scales. Environmental surveys indicate a large unexplored diversity and recent efforts hinted at a certain diversity of yet undescribed, inconspicuous, scale-lacking Euglyphida. Here we describe Phaeobola aeris gen. nov., sp. nov. that shows a variety of morphological characters typical for the Euglyphida but lacks silica scales-instead, this species bears an agglutinated test. Neither its morphology nor phylogenetic placement allows its assignment to any currently described family. We erected the yet monospecific genus Phaeobola gen. nov., which with yet available data remain Euglyphida incertae sedis.     

Ultrastructure and Ecology of Calycomonas ovalis Wulff, 1919, (Chrysophyceae) and Its Redescription as a Testate Rhizopod,Paulinella ovalis N. Comb. (Filosea: Euglyphina)1

An exceptional bloom (10⁹ cells/liter) of a unicellular alga, Aureococcus anophagefferens, in Narragansett Bay, RI, was accompanied by unusually high numbers (6 times 10⁶ tests/liter) of vase-shaped cells of Calycomonas ovalis Wulff, hitherto considered a flagellated chrysophyte. Phase contrast light microscopy showed the characteristic oval lorica or test of C. ovalis, ca. 3.0 times 4.5 μm. Transmission electron microscopy of thin sections of natural populations revealed, however, that C. ovalis is actually a rhizopod within a test of electron-dense scales. This estuarine, planktonk testacean extends a pseudopodium through a narrow pseudostome and lacks chloroplasts or flagella. It is a bacterivore and feeds primarily on unicellular cyanobacteria. The morphology, ultrastructure, and cell division of C. ovalis are described. These characteristics place C. ovalis with the genus Paulinella (Sarcodina: Filosea: Euglyphina), which at present contains the single species, P. chromatophora Lauterbom. Calycomonas ovalis is thus assigned to Paulinella as P. ovalis n. comb.