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Protists
Kinds of Protists Terms modified by Protists Selected AbstractsMorphological and molecular analysis of bromeliad-inhabiting ciliates in EcuadorTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005MICAH SAUL DUNTHORN The microbial inhabitants of Neotropical forests are poorly known. According to Finlay (2002, Science, 296:1061,1063) the majority of taxa in tropical forests should be previously described elsewhere. Conversely, Foissner (1999, Protist, 150:363,368) points to examples of endemic protists, and states that while we can identify the common species there are few trained taxonomists to identify the rare ones in large sampling investigations. To test these hypotheses, I am following up on an initial study of Foissner et al. (2003, Europ. J. Protistol., 39:365,372) of the ciliates inhabiting waters in canopy, sub-canopy and terrestrial bromeliad tanks in two Ecuadorian forests. Using morphological (protargol, silver nitrate, and silver carbonate stains; scanning electron micrographs) and molecular methods (SSU and ITS sequencing) I will concentrate my investigations on the colpodid taxa found free-living in the bromeliad tanks in two Ecuadorian forests. If I find many new taxa, Finlay's hypothesis may not be applicable to atleast bromeliad-inhabiting ciliates. [source] Protists with different feeding modes change biofilm morphologyFEMS MICROBIOLOGY ECOLOGY, Issue 2 2009Anne Böhme Abstract The effect of Dexiostoma (filter feeder), Vannella, Chilodonella (raptorial feeders), Spumella, and Neobodo (direct interception feeders) on the morphology of multispecies bacterial biofilms was investigated in small flow cells. The filter feeder Dexiostoma campylum did not alter biofilm volume and porosity but stimulated the formation of larger microcolonies compared with ungrazed biofilms. In contrast, the raptorial feeder Vannella sp. efficiently grazed bacteria from the biofilm surface, leading to smaller microcolonies and lower maximal and basal layer thickness compared with ungrazed biofilms. Microcolony formation was not stimulated in the presence of the sessile Spumella sp. Chilodonella uncinata rasped bacteria from the outer surface leading to mushroom-shaped microcolonies. In the presence of C. uncinata and Spumella sp., the biofilm volume was 2.5,6.3 times lower compared with ungrazed biofilms. However, the biofilm porosity and the ratio of biofilm surface area to biofilm volume were 1.5,3.7 and 1.2,1.8 times higher, respectively. Thus, exchange of nutrients and gases between the biofilm and its surrounding fluid should also be improved in deeper biofilm layers, hence accelerating microbial growth. [source] Ontogenetic Shifts in the Ability of the Cladoceran, Moina macrocopa Straus and Ceriodaphnia cornuta Sars to Utilize Ciliated Protists as Food SourceINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2008Ram Kumar Abstract The ontogenetic diet shifts and age specific ability of the two cladoceran species Moina macrocopa and Ceriodaphnia cornuta to derive energy from ciliated protists have been investigated in laboratory. The postembryonic developmental rates and life table demography (longevity, age and size at first reproduction, fecundity and intrinsic rate of natural increase) of the cladocerans have been elucidated on algae (Chlorella vulgaris) and the ciliated protists (Tetrahymena pyriformis, Colpoda (c.f.) steini) as food. For either of the cladoceran, the somatic growth rate and average body size at first reproduction were higher with algal diet. During initial stages of development (0,5 days), either cladoceran realized higher rate of somatic growth on algal diet, subsequently ciliated protists supported significantly higher growth rate than the alga. Algal and ciliate diets did not differ in maximum body size (C. cornuta: 539,554 ,m; M. macrocopa: 1274.8,1309 ,m) reached by either of the cladocerans. The maximum body sizes were larger than size at first reproduction with either of the ciliated protists, however, with algal diet the maximum body sizes did not differ from the size at first reproduction in each case. In case of C. cornuta the generation time (20.5 ± 0.3 days on ciliate; 15.6 ± 0.17 days on algal diet), reproductive rates (net reproductive rate: 20.05 ± 3.2 on ciliate; 15.5 ± 1.2 on algal diet), and average life expectancy at hatching (27 ± 0.8 days on ciliate; 22.7 ± 0.71 days on alga) were higher, whereas the size at first reproduction (482 ,m on ciliate; 521 ,m on alga) was smaller with the ciliate than with an algal diet. The algal and the ciliate diets did not differ in survival (life expectancy at hatching: 9.2 ± 0.7 days) and fecundity (NRR: 23.6 ± 2.4) for M. macrocopa. The two ciliates used in the experiment did not differ in their performance as food source for either cladoceran species. Our results suggest that both the cladoceran species are able to utilize smaller ciliate (e.g., T. pyriformis, C. (c.f.) steini) as food; however with differential ability to derive energy from the ciliate diet and this ability is size and age structured in both cases. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] From the Editors: Describing New Taxa of Unicellular ProtistsTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 5 2009DENIS H. LYNN EDITOR-IN-CHIEF [source] The Role of Acidocalcisomes in Parasitic Protists,THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 3 2009SILVIA N. J. MORENO ABSTRACT. Acidocalcisomes are acidic organelles with a high concentration of phosphorus present as pyrophosphate (PPi) and polyphosphate (poly P) complexed with calcium and other cations. The acidocalcisome membrane contains a number of pumps (Ca2+ -ATPase, V-H+ -ATPase, H+ -PPase), exchangers (Na+/H+, Ca2+/H+), and channels (aquaporins), while its matrix contains enzymes related to PPi and poly P metabolism. Acidocalcisomes have been observed in pathogenic, as well as non-pathogenic prokaryotes and eukaryotes, e.g. Chlamydomonas reinhardtii, and Dictyostelium discoideum. Some of the potential functions of the acidocalcisome are the storage of cations and phosphorus, the participation of phosphorus in PPi and poly P metabolism, calcium homeostasis, maintenance of intracellular pH homeostasis, and osmoregulation. In addition, acidocalcisomes resemble lysosome-related organelles (LRO) from mammalian cells in many of their properties. For example, we found that platelet dense granules, which are LROs, are very similar to acidocalcisomes. They share a similar size, acidic properties, and both contain PPi, poly P, and calcium. Recent work that indicates that they also share the system for targeting of their membrane proteins through adaptor protein 3 reinforces this concept. The fact that acidocalcisomes interact with other organelles in parasitic protists, e.g. the contractile vacuole in Trypanosoma cruzi, and other vacuoles observed in Toxoplasma gondii, suggests that these cellular compartments may be associated with the endosomal/lysosomal pathway. [source] The Role of Amoeboid Protists and the Microbial Community in Moss-Rich Terrestrial Ecosystems: Biogeochemical Implications for the Carbon Budget and Carbon Cycle, Especially at Higher Latitudes,THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 3 2008O. ROGER ANDERSON ABSTRACT. Moss-rich terrestrial communities are widely distributed in low- and high-latitude environments, covering vast surface areas in the boreal forests and tundra. The microbial biota in these organic-rich communities may contribute substantially to the carbon budget of terrestrial communities and the carbon cycle on a global scale. Recent research is reported on the carbon content of microbial communities in some temperate and high-latitude moss communities. The total carbon content and potential respiratory carbon dioxide (CO2) efflux is reported for bacteria, microflagellates, naked amoebae, and testate amoebae within sampling sites at a northeastern forest and the tundra at Toolik, Alaska. Quantitative models of the predicted total CO2 efflux from the microbes, based on microscopic observations and enumeration of the microbiota in samples from the research sites, are described and predictions are compared with published field-based data of CO2 efflux. The significance of the predictions for climate change and global warming are discussed. [source] The International Workshops on Opportunistic ProtistsTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2006EDNA S. KANESHIRO [source] A Java Applet for Exploring the New Higher Level Classification of Eukaryotes with Emphasis on the Taxonomy of ProtistsTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 5 2006MATTHIAS WOLF ABSTRACT. We have converted the hierarchically organized new higher level classification of eukaryotes with emphasis on the taxonomy of protists proposed by Adl et al. into an interactive and dynamic Java applet. The current version of the applet can be accessed via http://phylogenetics.bioapps.biozentrum.uni-wuerzburg.de/etv. We use the layout from a Degree-of-Interest tree (DOITree) that effectively displays all the taxonomic information as well as the phylogenetic relationships described in the original article by Adl et al. The tree was made using the Prefuse Toolkit for interactive information visualization. All browsers capable of using Java applets will be able to view the tree. The applet is freely available for scientists, teachers, and students. [source] The New Higher Level Classification of Eukaryotes with Emphasis on the Taxonomy of ProtistsTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 5 2005SINA M. ADL Abstract. This revision of the classification of unicellular eukaryotes updates that of Levine et al. (1980) for the protozoa and expands it to include other protists. Whereas the previous revision was primarily to incorporate the results of ultrastructural studies, this revision incorporates results from both ultrastructural research since 1980 and molecular phylogenetic studies. We propose a scheme that is based on nameless ranked systematics. The vocabulary of the taxonomy is updated, particularly to clarify the naming of groups that have been repositioned. We recognize six clusters of eukaryotes that may represent the basic groupings similar to traditional "kingdoms." The multicellular lineages emerged from within monophyletic protist lineages: animals and fungi from Opisthokonta, plants from Archaeplastida, and brown algae from Stramenopiles. [source] Introductory Remarks: Advances In The Molecular Ecology of Protists,THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005DAVID A. CARON No abstract is available for this article. [source] Effects of Xenobiotic Compounds on Cell Activities in Euplotes crassusTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005FRANCESCA TRIELLI It is now widely accepted that Protists are relevant bioassays to be exploited for the study of environmental modifications due to the presence of xenobiotic compounds. In this work, we evaluated the possibility of utilizing Euplotes crassus, an interstitial marine ciliate, for the pre-chemical screening of environmental sites, such as estuarine and coastal sediments. With this aim, we tested the sensitivity of E. crassus to exposure to three classes of pollutants: an organophosphate neurotoxic drug, basudin, largely used for pest control in agricultural sites, a toxic heavy metal, mercury (HgCl2), and an aromatic polycyclic hydrocarbon, benzopyrene (BP). We found a dose-dependent effect of these compounds on cell viability at concentrations ranging from 1/102 v/v to 1/107 v/v for basudin, from 5 ,M to 0.1 ,M for HgCl2, and from 50 ,M to 1 ,M for BP. In particular, 100% mortality was caused by a 1-h exposure to 1/105 v/v basudin, or 2 ,M HgCl2, or 25 ,M BP, and by a 24-h exposure to 1/106 v/v basudin, 0.5 ,M HgCl2, or 5 ,M BP. A significant decrease in the daily mean fission rate (P<0.001) was found after exposure to 1/107 v/v basudin, or 0.25 ,M HgCl2, or 1 ,M BP. Moreover, as it is well known that the inhibition of acetylcholinesterase (AChE) activity represents a specific biomarker for neurotoxic drugs, we first detected this enzyme activity in E. crassus, using cytochemical, spectrophotometric, and electrophoretic methods; then, AChE activity was characterized by its sensitivity to specific AChE inhibitors and to variations in pH and temperature. Like AChE present in higher organisms, the AChE activity detected in E. crassus was inhibited by exposure to basudin. Conversely, exposure to HgCl2, or PB did not inhibit AChE activity, but caused a significant reduction in lysosomal membrane stability. [source] A Multidisciplinary Approach to Describe Protists: Redescriptions of Novistrombidium testaceum Anigstein 1914 and Strombidium inclinatumMontagnes, Taylor, and Lynn 1990 (Ciliophora, Oligotrichia)THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 3 2003LETIZIA MODEO ABSTRACT. We combined behavioral, morphological (live, stained, scanning and transmission electron-microscope), and molecular data to redescribe two common, intertidal oligotrich ciliates, Novistrombidium testaceum and Strombidium inclinatum. Both species were collected from a rocky shore near Leghorn, Ligurian Sea. A literature review revealed four morphotypes of Novistrombidium testaceum that differ in subtle ways, including oral morphology. These differences may be diagnostic, but we do not consider them sufficient to distinguish different taxa. Although other studies have synonymised Strombidium inclinatum and S. sulcatum, based on oral structures, size, and nuclear structure, there are morphological distinctions between them. In particular, the present study supports a lack of anterior protuberance in both live and preserved S. inclinatum, while S. sulcatum possesses a protuberance. The 18S rDNA molecular data, in accordance with morphological and ultrastructural observations, indicate that the Strombidiida (Oligotrichia) constitute a well-supported clade. The separation of the genera within this clade, even between Novistrombidium and Strombidium, remains unresolved, and the analysis of more species is required. Finally, we recommend that when possible, ecologists, morphological taxon-omists, and molecular biologists combine their expertise to provide comprehensive taxonomic descriptions. [source] Sulfur assimilation by Oxyrrhis marina feeding on a 35S-DMSP-labelled preyENVIRONMENTAL MICROBIOLOGY, Issue 12 2009Violeta Saló Summary A laboratory grazing experiment was conducted with the aim of quantifying the sulfur assimilation by a herbivore protist feeding on a dimethylsulfoniopropionate (DMSP)-containing phytoplankter. When supplied with dissolved 35S-DMSP, cultures of an axenic strain of the diatom Thalassiosira pseudonana took up 60,95% of the added radioisotope and accumulated it untransformed in the cytoplasm. Radiolabelled diatom cells were offered as prey to the heterotrophic dinoflagellate Oxyrrhis marina. After 32 h in the dark, all the prey had been grazed and digested, leaving only radiolabelled O. marina in the grazing bottles and thus providing an estimate of the percentage of DMSP-sulfur retained by the predator. Subsequent precipitation with cold trichloroacetic acid (TCA) provided the fraction of retained DMSP-S that had been assimilated into the micrograzer macromolecules. In parallel incubations with predator and dissolved 35S-DMSP only (no prey), O. marina (and their closely associated bacteria) took up the radiolabelled substrate osmotrophically to an activity of 0.04 dpm cell,1 and assimilated it all into macromolecules. By correcting grazing 35S-DMSP assimilation for osmotrophic 35S-DMSP assimilation, and comparing it with the ingested radioisotope, the percentage of ingested DMSP-sulfur retained and assimilated by the predator was determined to be 32 ± 4%. This is the first study that provides direct evidence that ingestion of a DMSP-containing prey supplies structural sulfur to a herbivore protist and that quantifies this assimilative supply at one-third of ingested DMSP. [source] Ecological niche partitioning in the picoplanktonic green alga Micromonas pusilla: evidence from environmental surveys using phylogenetic probesENVIRONMENTAL MICROBIOLOGY, Issue 9 2008Elodie Foulon Summary Very few studies have analysed the niches of pelagic protist in details. This is because for most protists, both an accurate species definition and methods for routine detection and quantification of cells are lacking. The morphospecies Micromonas pusilla, a marine unicellular green alga, is the most ubiquitous and cosmopolitan picoeukaryote described to date. This species comprises several independent genetic lineages or clades, which are not currently distinguishable based on comparison of their morphology or biogeographical distribution. Molecular probes were used to detect and quantify the genetic clades of M. pusilla in samples from temperate, polar and tropical environments in order to assess potential ecological niche partitioning. The three clades were detected in all biogeographical regions studied and were commonly found in sympatry. Cell abundances recorded for clades A and B were high, especially at coastal stations. Clade C, when detected, was always at low abundances and is suggested to be a low-light clade. Shifts in the contribution of clades to total M. pusilla abundance were observed along environmental gradients, both at local and basin-wide scales. This suggests that the phylogenetic clades occupy specific niches and confirms the existence of cryptic species within the morphospecies M. pusilla. Parameters which can precisely explain the distribution of these cryptic species remain to be elucidated. [source] Recent evolutionary diversification of a protist lineageENVIRONMENTAL MICROBIOLOGY, Issue 5 2008Ramiro Logares Summary Here, we have identified a protist (dinoflagellate) lineage that has diversified recently in evolutionary terms. The species members of this lineage inhabit cold-water marine and lacustrine habitats, which are distributed along a broad range of salinities (0,32) and geographic distances (0,18 000 km). Moreover, the species present different degrees of morphological and sometimes physiological variability. Altogether, we analysed 30 strains, generating 55 new DNA sequences. The nuclear ribosomal DNA (nrDNA) sequences (including rapidly evolving introns) were very similar or identical among all the analysed isolates. This very low nrDNA differentiation was contrasted by a relatively high cytochrome b (COB) mitochondrial DNA (mtDNA) polymorphism, even though the COB evolves very slowly in dinoflagellates. The 16 Maximum Likelihood and Bayesian phylogenies constructed using nr/mtDNA indicated that the studied cold-water dinoflagellates constitute a monophyletic group (supported also by the morphological analyses), which appears to be evolutionary related to marine-brackish and sometimes toxic Pfiesteria species. We conclude that the studied dinoflagellates belong to a lineage which has diversified recently and spread, sometimes over long distances, across low-temperature environments which differ markedly in ecology (marine versus lacustrine communities) and salinity. Probably, this evolutionary diversification was promoted by the variety of natural selection regimes encountered in the different environments. [source] Identification and characterization of ectosymbionts of distinct lineages in Bacteroidales attached to flagellated protists in the gut of termites and a wood-feeding cockroachENVIRONMENTAL MICROBIOLOGY, Issue 1 2006Satoko Noda Summary Bacterial attachments to nearly the entire surface of flagellated protists in the guts of termites and the wood-feeding cockroach Cryptocercus are often observed. Based on the polymerase chain reaction-amplified 16S rRNA gene sequences, we investigated the phylogenetic relationships of the rod-shaped, attached bacteria (ectosymbionts) of several protist species from five host taxa and confirmed their identity by fluorescence in situ hybridizations. These ectosymbionts are affiliated with the order Bacteroidales but formed three distinct lineages, each of which may represent novel bacterial genera. One lineage consisted of the closely related ectosymbionts of two species of the protist genus Devescovina (Cristamonadida). The second lineage comprised three phylotypes identified from the protist Streblomastix sp. (Oxymonadida). The third lineage included ectosymbionts of the three protist genera Hoplonympha, Barbulanympha and Urinympha in the family Hoplonymphidae (Trichonymphida). The ultrastructural observations indicated that these rod-shaped ectosymbionts share morphological similarities of their cell walls and their point of attachment with the protist but differ in shape. Elongated forms of the ectosymbionts appeared in all the three lineages. The protist cells Streblomastix sp. and Hoplonympha sp. display deep furrows and vane-like structures, but these impressive structures are probably evolutionarily convergent because both the host protists and their ectosymbionts are distantly related. [source] Bacterivorous grazers facilitate organic matter decomposition: a stoichiometric modeling approachFEMS MICROBIOLOGY ECOLOGY, Issue 2 2009Hao Wang Abstract There is widespread empirical evidence that protist grazing on bacteria reduces bacterial abundances but increases bacteria-mediated decomposition of organic matter. This paradox has been noted repeatedly in the microbiology literature but lacks a generally accepted mechanistic explanation. To explain this paradox quantitatively, we develop a bacteria-grazer model of organic matter decomposition that incorporates protozoa-driven nutrient recycling and stoichiometry. Unlike previous efforts, the current model includes explicit limitation, via Liebig's law of minimum, by two possible factors, nutrient and carbon densities, as well as their relative ratios in bacteria and grazers. Our model shows two principal results: (1) when the environment is carbon limiting, organic matter can always be decomposed completely, regardless of the presence/absence of grazers; (2) when the environment is nutrient (such as nitrogen) limiting, it is possible for organic matter to be completely decomposed in the presence, but not absence, of grazers. Grazers facilitate decomposition by releasing nutrients back into the environment, which would otherwise be limiting, while preying upon bacteria. Model analysis reveals that facilitation of organic matter decomposition by grazers is positively related to the stoichiometric difference between bacteria and grazers. In addition, we predict the existence of an optimal density range of introduced grazers, which maximally facilitate the decomposition of organic matter in a fixed time period. This optimal range reflects a trade-off between grazer-induced nutrient recycling and grazer-induced mortality of bacteria. [source] Spatial variation in population growth rate and community structure affects local and regional dynamicsJOURNAL OF ANIMAL ECOLOGY, Issue 6 2008M. Kurtis Trzcinski Summary 1Theory predicting that populations with high maximum rates of increase (rmax) will be less stable, and that metapopulations with high average rmax will be less synchronous, was tested using a small protist, Bodo, that inhabits pitcher plant leaves (Sarracenia purpurea L.). The effects of predators and resources on these relationships were also determined. 2Abundance data collected for a total of 60 populations of Bodo, over a period of 3 months, at six sites in three bogs in eastern Canada, were used to test these predictions. Mosquitoes were manipulated in half the leaves partway through the season to increase the range of predation rates. 3Dynamics differed greatly among leaves and sites, but most populations exhibited one or more episodes of rapid increase followed by a population crash. Estimates of rmax obtained using a linear mixed-effects model, ranged from 1·5 to 2·7 per day. Resource levels (captured insect) and midge abundances affected rmax. 4Higher rmax was associated with greater temporal variability and lower synchrony as predicted. However, in contrast to expectations, populations with higher rmax also had lower mean abundance and were more suppressed by predators. 5This study demonstrates that the link between rmax and temporal variability is key to understanding the dynamics of populations that spend little time near equilibrium, and to predicting and interpreting the effects of community structure on the dynamics of such populations. [source] Factors Affecting Preference Responses of the Freshwater Ciliate Uronema nigricans to Bacterial PreyTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2009BEGOÑA AYO ABSTRACT. To enhance our understanding of the factors affecting feeding selectivity of bacterivorous protists in aquatic systems, we examined the preference responses of the freshwater ciliate Uronema nigricans towards three bacterial prey taxa, Pseudomonas luteola, Serratia rubidaea, and Aeromonas hydrophila. Potential factors influencing the predator,prey contact rate included the previous feeding history of the ciliate and physiological state of bacteria. Preference indexes were obtained from multiple-choice mazes in which ciliates moved preferentially towards alternative bacteria or the prey species on which they had been feeding. Uronema nigricans showed differential attraction towards the offered prey types, and these preferences varied as a function of the ciliate feeding history: U. nigricans growing on P. luteola showed lower preference responses towards the offered bacteria than U. nigricans growing on S. rubidaea. The bacteria in stationary phase elicited a higher degree of attraction than bacteria in exponential phase, probably due to a higher concentration of carbohydrates in the former. Therefore, this protist will preferentially swim towards bacteria in stationary growth phase, although the degree of this response will be affected by the recent feeding history of the ciliate. [source] In Vitro Culture of the Obligate Parasite Spongospora subterranea (Cercozoa; Plasmodiophorida) Associated with Root-Inducing Transferred-DNA Transformed Potato Hairy RootsTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 6 2007XINSHUN QU ABSTRACT. Spongospora subterranea is a soil-borne, obligate parasitic protist that causes powdery scab of potatoes. In this study, an in vitro culture system was developed for the maintenance and proliferation of the protist in potato hairy roots. The hairy roots of potato were induced in vitro with Agrobacterium rhizogenes. Cystosori of S. subterranea from potato scab lesions were surface disinfested and used to inoculate potato hairy roots. Plasmodia, zoosporangia, and cystosori were observed microscopically in the hairy roots within 6 wk after inoculation, indicating the completion of the life cycle of S. subterranea in vitro. This is the first in vitro culture system for S. subterranea, and will be a valuable tool to study fundamental and practical aspects of the biology of the parasite. [source] There are High Levels of Functional and Genetic Diversity in Oxyrrhis marinaTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 3 2005CHRIS D. LOWE Abstract. Oxyrrhis marina, a widely distributed marine protist, is used to model heterotrophic flagellate responses in microbial food webs. Although clonal variability occurs in protists, assessments of intraspecific diversity are rare; such assessments are critical, particularly where species are used as models in ecological studies. To address the extent of intraspecific variation within O. marina, we assessed diversity among 11 strains using 5.8S rDNA and ITS sequences. The 5.8S rDNA and ITS regions revealed high divergence between strains: 63.1% between the most diverse. To compare O. marina diversity relative to other alveolates, 18S rDNA sequences for five strains were analysed with sequences from representatives of the major alveolate groups. 18S rDNA also revealed high divergence in O. marina. Additionally, consistent with phylogenies based on protein coding genes, maximum likelihood analysis indicated that O. marina was monophyletic and ancestral to the dinoflagellates. To assess ecophysiological differences, growth rates of seven O. marina strains were measured at 10 salinities (10,55,). Two salinity responses occurred: one group achieved highest growth rates at high salinities; the other grew best at low salinities. There was no clear correlation between molecular, ecophysiological, or geographical differences. However, salinity tolerance was associated with habitat type: intertidal strains grew best at high salinities; open-water strains grew best at low salinities. These data indicate the need to examine many strains of a species in both phylogenetic and ecological studies, especially where key-species are used to model ecological processes. [source] Growth of the vacuoleless mutant of Tetrahymena thermophila NP1 in phytateTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005SAMANTHA WEBB Phytate, the salt form of phytic acid, is the major store of phosphate in seeds and grain. Since non-ruminant farm animals poorly digest phytate, it is also a source of environmental phosphate contamination in agricultural areas. We are using Tetrahymena, a ciliated protist with multiple routes for nutrient assimilation, as a model to investigate the contribution of heterotrophic protists to the environmental cycling of phosphate from phytate. This ciliate has the ability to grow on phytate as the sole phosphate source (Ziemkiewicz, H. T., Johnson, M. D. & Smith-Somerville, H. E. 2002. J. Eukaryot. Microbiol., 49:428). Tetrahymena thermophila NP1, a temperature-sensitive vacuoleless mutant (ATCC #50202), provides a way to separate membrane transport from uptake through phagosomes, and to assess the importance of each mechanism. This cell grows equally well at the permissive and non-permissive temperatures with either phytate or inorganic phosphate as the phosphate source. Our results demonstrate that phagosomes are not required to use the phosphate from phytate. [source] The response of protist and metazoan communities in permeable pavement structures to high oil loadingsTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005S. J. COUPE Permeable pavement structures (PPS) have been demonstrated to provide an efficient and sustainable method of controlling urban derived hydrocarbon contamination. Until recently, laboratory PPS mesocosm models have used crushed granite as the load bearing sub-base material. However, the use of virgin stone may not be the optimal choice of substrate, as this is not necessarily sustainable or cost effective in the long term when compared to the use of recycled materials. However, recycled materials such as waste concrete may change the environmental conditions in PPS mesocosms, and the characteristics of the eukaryotic community may become different from those which have been previously described. In the current experiment, granite and recycled concrete sub-base materials were compared for their ability to retain 900 g/m2 of clean mineral oil applied to the mesocosm surface. It was observed that, even at this very high oil loading, 99.95% of the applied oil was retained within granite and concrete-based structures, but the effluent was two pH units more alkaline in concrete mesocosms than granite. The eukaryotic microfauna in the effluent from both mesocosm types showed a ten-fold increase in protist abundance, and a doubling in the number of protist genera, compared with earlier work using only 18 g/m2 of applied oil. Five genera of testate amoebae not previously recorded in PPS were identified, these included Arcella, Assulina, Cryptodifflugia, Cyclopyxis and Difflugia in addition to the three genera observed previously using the lower oil application. Metazoan abundances increased from 1.5 × 101 organisms per ml using the lower oil loadings to 2.0 × 103/ml in the current experiment. Rotifers and nematodes were the most numerous, but tardigrades were also observed in both concrete and granite-based mesocosms. Despite the differences in effluent pH, it was apparent that there were only marginal differences in the eukaryotic microbiology of the two mesocosm types. This was thought to be due to the layered structural arrangement of the pavement and the location of the highly oil-retentive polypropylene geotextile and extensive biofilm layer positioned above the concrete sub-base. Work is now underway to find oil loadings that will adversely affect the abundance and diversity of eukaryotic organisms in PPS mesocosms. [source] An insider's guide to the microtubule cytoskeleton of GiardiaCELLULAR MICROBIOLOGY, Issue 5 2010Scott C. Dawson Summary Giardia intestinalis is a zoonotic, parasitic protist with a complex microtubule cytoskeleton critical for motility, attachment, intracellular transport, cell division and transitioning between its two life cycle stages , the cyst and the trophozoite. This review focuses on the structures of the primary elements of the microtubule cytoskeleton and cytoskeletal dynamics throughout this complex giardial life cycle. The giardial cytoskeleton has both highly dynamic elements and more stable MT structures, including several novel structures like the ventral disc that change conformation via unknown mechanisms. While our knowledge of the giardial cytoskeleton is primarily cytological, the completed Giardia genome and recently developed reverse genetic tools affords an opportunity to uncover the mechanisms of Giardia's cytoskeletal dynamics. Fundamental areas of giardial cytoskeletal biology remain to be explored, including high resolution imaging and compositional characterization of cytoskeletal structures required for elucidating the molecular mechanisms of cytoskeletal functioning. [source] Cross-reactivity of antibodies to actin- depolymerizing factor/cofilin family proteins and identification of the major epitope recognized by a mammalian actin-depolymerizing factor/cofilin antibodyELECTROPHORESIS, Issue 15 2004Alisa E. Shaw Abstract Members of the actin-depolymerizing factor (ADF)/cofilin family of proteins are expressed in all eukaryotic cells. In higher vertebrates, cells often express as many as three different ADF/cofilin genes and each of these proteins may be phosphorylated on serine 3, giving rise to up to six different species. Also, many avian, amphibian, and invertebrate systems have been useful in studying different aspects of ADF/cofilin function. Antibodies have been prepared against different members of the ADF/cofilin family, but no systematic examination of their cross-reactivity has been reported. Although ADF and cofilins within a single vertebrate species have about a 70% sequence homology, antibodies often differentiate between these proteins. Here, Western blotting was used with chemiluminescence substrates of different sensitivities to determine the relative immunoreactivities of different polyclonal rabbit antibodies and a mouse monoclonal antibody to purified ADF/cofilins from plants, protists, nematodes, insects, echinoderms, birds, and mammals. From immunocross-reactivities and sequence alignments, the principal epitope in mammalian ADF and cofilin-1 recognized by an antibody raised against avian ADF was identified. The specificity of an antibody to the phosphopeptide epitope of metazoan ADF/cofilins was confirmed by two-dimensional (2-D) immunoblot analysis. Futhermore, this bank of antibodies was used to identify by Western blotting a putative member of the ADF/cofilin family in the sea slug, Aplysia californica. [source] Use of stable isotope-labelled cells to identify active grazers of picocyanobacteria in ocean surface watersENVIRONMENTAL MICROBIOLOGY, Issue 2 2009Jorge Frias-Lopez Summary Prochlorococcus and Synechococcus are the two most abundant marine cyanobacteria. They represent a significant fraction of the total primary production of the world oceans and comprise a major fraction of the prey biomass available to phagotrophic protists. Despite relatively rapid growth rates, picocyanobacterial cell densities in open-ocean surface waters remain fairly constant, implying steady mortality due to viral infection and consumption by predators. There have been several studies on grazing by specific protists on Prochlorococcus and Synechococcus in culture, and of cell loss rates due to overall grazing in the field. However, the specific sources of mortality of these primary producers in the wild remain unknown. Here, we use a modification of the RNA stable isotope probing technique (RNA-SIP), which involves adding labelled cells to natural seawater, to identify active predators that are specifically consuming Prochlorococcus and Synechococcus in the surface waters of the Pacific Ocean. Four major groups were identified as having their 18S rRNA highly labelled: Prymnesiophyceae (Haptophyta), Dictyochophyceae (Stramenopiles), Bolidomonas (Stramenopiles) and Dinoflagellata (Alveolata). For the first three of these, the closest relative of the sequences identified was a photosynthetic organism, indicating the presence of mixotrophs among picocyanobacterial predators. We conclude that the use of RNA-SIP is a useful method to identity specific predators for picocyanobacteria in situ, and that the method could possibly be used to identify other bacterial predators important in the microbial food-web. [source] Ecological niche partitioning in the picoplanktonic green alga Micromonas pusilla: evidence from environmental surveys using phylogenetic probesENVIRONMENTAL MICROBIOLOGY, Issue 9 2008Elodie Foulon Summary Very few studies have analysed the niches of pelagic protist in details. This is because for most protists, both an accurate species definition and methods for routine detection and quantification of cells are lacking. The morphospecies Micromonas pusilla, a marine unicellular green alga, is the most ubiquitous and cosmopolitan picoeukaryote described to date. This species comprises several independent genetic lineages or clades, which are not currently distinguishable based on comparison of their morphology or biogeographical distribution. Molecular probes were used to detect and quantify the genetic clades of M. pusilla in samples from temperate, polar and tropical environments in order to assess potential ecological niche partitioning. The three clades were detected in all biogeographical regions studied and were commonly found in sympatry. Cell abundances recorded for clades A and B were high, especially at coastal stations. Clade C, when detected, was always at low abundances and is suggested to be a low-light clade. Shifts in the contribution of clades to total M. pusilla abundance were observed along environmental gradients, both at local and basin-wide scales. This suggests that the phylogenetic clades occupy specific niches and confirms the existence of cryptic species within the morphospecies M. pusilla. Parameters which can precisely explain the distribution of these cryptic species remain to be elucidated. [source] A methane-driven microbial food web in a wetland rice soilENVIRONMENTAL MICROBIOLOGY, Issue 12 2007Jun Murase Summary Methane oxidation is a key process controlling methane emission from anoxic habitats into the atmosphere. Methanotrophs, responsible for aerobic methane oxidation, do not only oxidize but also assimilate methane. Once assimilated, methane carbon may be utilized by other organisms. Here we report on a microbial food web in a rice field soil driven by methane. A thin layer of water-saturated rice field soil was incubated under opposing gradients of oxygen and 13C-labelled methane. Bacterial and eukaryotic communities incorporating methane carbon were analysed by RNA-stable isotope probing (SIP). Terminal restriction fragment length polymorphism (T-RFLP) and cloning showed that methanotrophs were the most prominent group of bacteria incorporating methane carbon. In addition, a few Myxobacteria -related sequences were obtained from the ,heavy' rRNA fraction. Denaturing gradient gel electrophoresis (DGGE) targeting 18S rRNA detected various groups of protists in the ,heavy' rRNA fraction including naked amoeba (Lobosea and Heterolobosea), ciliates (Colpodea) and flagellates (Cercozoa). Incubation of soil under different methane concentrations in air resulted in the development of distinct protozoan communities. These results suggest that methane carbon is incorporated into non-methanotrophic pro- and microeukaryotes probably via grazing, and that methane oxidation is a shaping force of the microeukaryotic community depending on methane availability. [source] Crash of a population of the marine heterotrophic flagellate Cafeteria roenbergensis by viral infectionENVIRONMENTAL MICROBIOLOGY, Issue 11 2007Ramon Massana Summary Viruses are known as important mortality agents of marine microorganisms. Most studies focus on bacterial and algal viruses, and few reports exist on viruses infecting marine heterotrophic protists. Here we show results from several incubations initiated with a microbial assemblage from the central Indian Ocean and amended with different amounts of organic matter. Heterotrophic flagellates developed up to 30 000 cells ml,1 in the most enriched incubation. A 18S rDNA clone library and fluorescent in situ hybridization counts with newly designed probes indicated that the peak was formed by Cafeteria roenbergensis and Caecitellus paraparvulus (90% and 10% of the cells respectively). Both taxa were below detection in the original sample, indicating a strong positive selective bias during the enrichment. During the peak, C. roenbergensis cells were observed with virus-like particles in the cytoplasm, and 4 days later this taxa could not be detected. Transmission electron microscopy confirmed the viral nature of these particles, which were large (280 nm), had double-stranded DNA, and were produced with a burst size of ,70. This virus was specific of C. roenbergensis as neither C. paraparvulus that was never seen infected, nor other flagellate taxa that developed in later stages of the incubation, appeared attacked. This is one of the few reports on a heterotrophic flagellate virus and the implications of this finding in the Indian Ocean are discussed. [source] Vertical distribution of picoeukaryotic diversity in the Sargasso SeaENVIRONMENTAL MICROBIOLOGY, Issue 5 2007Fabrice Not Summary Eukaryotic molecular diversity within the picoplanktonic size-fraction has primarily been studied in marine surface waters. Here, the vertical distribution of picoeukaryotic diversity was investigated in the Sargasso Sea from euphotic to abyssal waters, using size-fractionated samples (< 2 ,m). 18S rRNA gene clone libraries were used to generate sequences from euphotic zone samples (deep chlorophyll maximum to the surface); the permanent thermocline (500 m); and the pelagic deep-sea (3000 m). Euphotic zone and deep-sea data contrasted strongly, the former displaying greater diversity at the first-rank taxon level, based on 232 nearly full-length sequences. Deep-sea sequences belonged almost exclusively to the Alveolata and Radiolaria, while surface samples also contained known and putative photosynthetic groups, such as unique Chlorarachniophyta and Chrysophyceae sequences. Phylogenetic analyses placed most Alveolata and Stramenopile sequences within previously reported ,environmental' clades, i.e. clades within the Novel Alveolate groups I and II (NAI and NAII), or the novel Marine Stramenopiles (MAST). However, some deep-sea NAII formed distinct, bootstrap supported clades. Stramenopiles were recovered from the euphotic zone only, although many MAST are reportedly heterotrophic, making the observed distribution a point for further investigation. An unexpectedly high proportion of radiolarian sequences were recovered. From these, five environmental radiolarian clades, RAD-I to RAD-V, were identified. RAD-IV and RAD-V were composed of Taxopodida-like sequences, with the former solely containing Sargasso Sea sequences, although from all depth zones sampled. Our findings highlight the vast diversity of these protists, most of which remain uncultured and of unknown ecological function. [source] | ||||||||||||||||||||||||||||