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1
Jing, H., E. Rocke, L. Kong, X. Xia, H. Liu, and M. R. Landry. "Protist communities in a marine oxygen minimum zone off Costa Rica by 454 pyrosequencing." Biogeosciences Discussions 12, no. 16 (August 20, 2015): 13483–509. http://dx.doi.org/10.5194/bgd-12-13483-2015.
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Abstract. Marine planktonic protists, including microalgae and protistan grazers, are an important contributor to global primary production and carbon and mineral cycles, however, little is known about their population shifts along the oxic-anoxic gradient in the water column. We used 454 pyrosequencing of the 18S rRNA gene and gene transcripts to study the community composition of whole and active protists throughout a water column in the Costa Rica Dome, where a stable oxygen minimum zone (OMZ) exists at a depth of 400~700 m. A clear shift of protist composition from photosynthetic Dinoflagellates in the surface to potential parasitic Dinoflagellates and Ciliates in the deeper water was revealed along the vertical profile at both rRNA and rDNA levels. Those protist groups recovered only at the rDNA level represent either lysed aggregates sinking from the upper waters or potential hosts for parasitic groups. UPGMA clustering demonstrated that total and active protists in the anoxic core of OMZ (550 m) were distinct from those in other water depths. The reduced community diversity and presence of a parasitic/symbiotic trophic lifestyle in the OMZ, especially the anoxic core, suggests that OMZs can exert a selective pressure on protist communities. Such changes in community structure and a shift in trophic lifestyle could result in a modulation of the microbial loop and associated biogeochemical cycling.
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Andersen, Robert A. "What to do with protists?" Australian Systematic Botany 11, no. 2 (1998): 185. http://dx.doi.org/10.1071/sb97011.
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The definition of ‘protists’ has changed over time, once including all living organisms which were neither plant nor animal, now including a multitude of organisms that cannot be assembled into a monophyletic group. Protists were once subdivided into algae, fungi and protozoa, based upon mode of nutrition, and further subdivided based upon the dominate life history stage (e.g. flagellate, amoeboid, coccoid), however, studies during the past 40 years have shown that these divisions are artificial. Electron microscopic studies, as well as a revival of the Endosymbiotic Theory for the origin of organelles, have caused a demolition of classical protistan taxonomy. Numerous new higher level taxa were described. Molecular studies, especially nucleotide sequence comparisons, have provided a new means for determining phylogenetic relationships. Although these molecular studies have not succeeded in providing an overall consensus classification for the protists, many advances have been made. It now appears that the protists are, at best, a grade, not a clade, and they do not form a monophyletic taxon (i.e. the Kingdom Protista cannot be recognised as a natural group). Despite this taxonomic limitation, there are advantages to maintaining the protists as an assemblage for ecological, biomedical or economic reasons. The biodiversity of protists is discussed along with remarks on their ecological and economic significance.
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Klepka, Verônica, Maria Julia Corazza, and Fagner De Souza. "John Hogg (1800-1869) e a descrição do quarto reino natural: Primigenum." História da Ciência e Ensino: construindo interfaces 18 (November 28, 2018): 125–39. http://dx.doi.org/10.23925/2178-2911.2018v18p125-139.
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ResumoAté o século XIX, organismos que, por indefinição ou por falta de caracteres distintivos claros, compartilhavam características com as plantas e/ou com os animais estavam distribuídos nos reinos vegetal ou animal. Novos conhecimentos tornaram necessária a criação de um agrupamento separado. Em 1860, o naturalista John Hogg revisa a separação feita pelo paleontólogo Richard Owen propondo modificações e a criação do quarto reino da natureza: o Primigenum, foco de debates conceituais ao longo de todo século XX até chegar ao que hoje conhecemos como Reino Protista. A tradução do trabalho de Hogg, lido para a Associação Britânica, em Oxford, no dia 28 de junho de 1860, é aqui apresentada. Palavras-Chave: Classificação biológica; Protistas; Seres Vivos.AbstractUntil the nineteenth century, organisms, of indefiniteness or lack of clear distinctive characters, shared features with the plants and / or animals were distributed in the plant and animal kingdom. New knowledge made necessary the creation of a separate grouping. In 1860, naturalist John Hogg review the separation maked for paleontologist Richard Owen proposing modifications and the creation of the fourth kingdom of nature: the Primigenum, focus of conceptual debates throughout the twentieth century to get to what we know today as the Kingdom Protist. The translation of Hogg, work read to British Association, in Oxford, on June 28, 1860, is presented here.Keywords: Biologic classification; Protists; Living Beings
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Zou, Songbao, Qianqian Zhang, and Jun Gong. "Comparative Transcriptomics Reveals Distinct Gene Expressions of a Model Ciliated Protozoan Feeding on Bacteria-Free Medium, Digestible, and Digestion-Resistant Bacteria." Microorganisms 8, no. 4 (April 13, 2020): 559. http://dx.doi.org/10.3390/microorganisms8040559.
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Bacterivory is an important ecological function of protists in natural ecosystems. However, there are diverse bacterial species resistant to protistan digestion, which reduces the carbon flow to higher trophic levels. So far, a molecular biological view of metabolic processes in heterotrophic protists during predation of bacterial preys of different digestibility is still lacking. In this study, we investigated the growth performance a ciliated protozoan Tetrahymena thermophila cultivated in a bacteria-free Super Proteose Peptone (SPP) medium (control), and in the media mixed with either a digestion-resistant bacterial species (DRB) or a digestible strain of E. coli (ECO). We found the protist population grew fastest in the SPP and slowest in the DRB treatment. Fluorescence in situ hybridization confirmed that there were indeed non-digested, viable bacteria in the ciliate cells fed with DRB, but none in other treatments. Comparative analysis of RNA-seq data showed that, relative to the control, 637 and 511 genes in T. thermophila were significantly and differentially expressed in the DRB and ECO treatments, respectively. The protistan expression of lysosomal proteases (especially papain-like cysteine proteinases), GH18 chitinases, and an isocitrate lyase were upregulated in both bacterial treatments. The genes encoding protease, glycosidase and involving glycolysis, TCA and glyoxylate cycles of carbon metabolic processes were higher expressed in the DRB treatment when compared with the ECO. Nevertheless, the genes for glutathione metabolism were more upregulated in the control than those in both bacterial treatments, regardless of the digestibility of the bacteria. The results of this study indicate that not only bacterial food but also digestibility of bacterial taxa modulate multiple metabolic processes in heterotrophic protists, which contribute to a better understanding of protistan bacterivory and bacteria-protists interactions on a molecular basis.
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Chauvier, G., and J. Mortier-Gabet. "Culture d’un Protiste pathogène isolé du système génital et de divers organes de Primates." Annales de Parasitologie Humaine et Comparée 62, no. 4 (1987): 294–300. http://dx.doi.org/10.1051/parasite/1987624294.
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Oliverio, Angela M., Stefan Geisen, Manuel Delgado-Baquerizo, Fernando T. Maestre, Benjamin L. Turner, and Noah Fierer. "The global-scale distributions of soil protists and their contributions to belowground systems." Science Advances 6, no. 4 (January 2020): eaax8787. http://dx.doi.org/10.1126/sciadv.aax8787.
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Protists are ubiquitous in soil, where they are key contributors to nutrient cycling and energy transfer. However, protists have received far less attention than other components of the soil microbiome. We used amplicon sequencing of soils from 180 locations across six continents to investigate the ecological preferences of protists and their functional contributions to belowground systems. We complemented these analyses with shotgun metagenomic sequencing of 46 soils to validate the identities of the more abundant protist lineages. We found that most soils are dominated by consumers, although parasites and phototrophs are particularly abundant in tropical and arid ecosystems, respectively. The best predictors of protist composition (primarily annual precipitation) are fundamentally distinct from those shaping bacterial and archaeal communities (namely, soil pH). Some protists and bacteria co-occur globally, highlighting the potential importance of these largely undescribed belowground interactions. Together, this study allowed us to identify the most abundant and ubiquitous protists living in soil, with our work providing a cross-ecosystem perspective on the factors structuring soil protist communities and their likely contributions to soil functioning.
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Zölffel, Michael, and Oliver Skibbe. "Rediscovery of the multiflagellated protist Paramastix conifera Skuja 1948 (Protista incertae sedis)." Nova Hedwigia 65, no. 1-4 (May 15, 1997): 443–52. http://dx.doi.org/10.1127/nova.hedwigia/65/1997/443.
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Jagus, Rosemary, Tsvetan R. Bachvaroff, Bhavesh Joshi, and Allen R. Place. "Diversity of Eukaryotic Translational Initiation Factor eIF4E in Protists." Comparative and Functional Genomics 2012 (2012): 1–21. http://dx.doi.org/10.1155/2012/134839.
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The greatest diversity of eukaryotic species is within the microbial eukaryotes, the protists, with plants and fungi/metazoa representing just two of the estimated seventy five lineages of eukaryotes. Protists are a diverse group characterized by unusual genome features and a wide range of genome sizes from 8.2 Mb in the apicomplexan parasiteBabesia bovisto 112,000-220,050 Mb in the dinoflagellateProrocentrum micans. Protists possess numerous cellular, molecular and biochemical traits not observed in “text-book” model organisms. These features challenge some of the concepts and assumptions about the regulation of gene expression in eukaryotes. Like multicellular eukaryotes, many protists encode multiple eIF4Es, but few functional studies have been undertaken except in parasitic species. An earlier phylogenetic analysis of protist eIF4Es indicated that they cannot be grouped within the three classes that describe eIF4E family members from multicellular organisms. Many more protist sequences are now available from which three clades can be recognized that are distinct from the plant/fungi/metazoan classes. Understanding of the protist eIF4Es will be facilitated as more sequences become available particularly for the under-represented opisthokonts and amoebozoa. Similarly, a better understanding of eIF4Es within each clade will develop as more functional studies of protist eIF4Es are completed.
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Shimada, Keisuke, Nathan Lo, Osamu Kitade, Akane Wakui, and Kiyoto Maekawa. "Cellulolytic Protist Numbers Rise and Fall Dramatically in Termite Queens and Kings during Colony Foundation." Eukaryotic Cell 12, no. 4 (February 2, 2013): 545–50. http://dx.doi.org/10.1128/ec.00286-12.
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ABSTRACTAmong the best-known examples of mutualistic symbioses is that between lower termites and the cellulolytic flagellate protists in their hindguts. Although the symbiosis in worker termites has attracted much attention, there have been only a few studies of protists in other castes. We have performed the first examination of protist population dynamics in queens and kings during termite colony foundation. Protist numbers, as well as measurements of hindgut and reproductive tissue sizes, were undertaken at five time points over 400 days in incipient colonies ofReticulitermes speratus, as well as in other castes of mature colonies of this species. We found that protist numbers increased dramatically in both queens and kings during the first 50 days of colony foundation but began to decrease by day 100, eventually disappearing by day 400. Hindgut width followed a pattern similar to that of protist numbers, while ovary and testis widths increased significantly only at day 400. Kings were found to contain higher numbers of protists than queens in incipient colonies, which may be linked to higher levels of nutrient transfer from kings to queens than vice versa, as is known in some other termite species. Protists were found to be abundant in soldiers from mature colonies but absent in neotenics. This probably reflects feeding of soldiers by workers via proctodeal trophallaxis and of reproductives via stomodeal trophallaxis. The results reveal the dynamic nature of protist numbers during colony foundation and highlight the trade-offs that exist between reproduction and parental care during this critical phase of the termite life cycle.
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Chauvier, G., and J. Mortier-Gabet. "Découverte d’un Protiste parasite, paraissant apparenté aux Acrasiés, dans l’appareil génital et certains organes de Primates." Annales de Parasitologie Humaine et Comparée 61, no. 4 (1986): 401–10. http://dx.doi.org/10.1051/parasite/1986614401.
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Hu, Sarah K., Erica L. Herrera, Amy R. Smith, Maria G. Pachiadaki, Virginia P. Edgcomb, Sean P. Sylva, Eric W. Chan, Jeffrey S. Seewald, Christopher R. German, and Julie A. Huber. "Protistan grazing impacts microbial communities and carbon cycling at deep-sea hydrothermal vents." Proceedings of the National Academy of Sciences 118, no. 29 (July 15, 2021): e2102674118. http://dx.doi.org/10.1073/pnas.2102674118.
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Microbial eukaryotes (or protists) in marine ecosystems are a link between primary producers and all higher trophic levels, and the rate at which heterotrophic protistan grazers consume microbial prey is a key mechanism for carbon transport and recycling in microbial food webs. At deep-sea hydrothermal vents, chemosynthetic bacteria and archaea form the base of a food web that functions in the absence of sunlight, but the role of protistan grazers in these highly productive ecosystems is largely unexplored. Here, we pair grazing experiments with a molecular survey to quantify protistan grazing and to characterize the composition of vent-associated protists in low-temperature diffuse venting fluids from Gorda Ridge in the northeast Pacific Ocean. Results reveal protists exert higher predation pressure at vents compared to the surrounding deep seawater environment and may account for consuming 28 to 62% of the daily stock of prokaryotic biomass within discharging hydrothermal vent fluids. The vent-associated protistan community was more species rich relative to the background deep sea, and patterns in the distribution and co-occurrence of vent microbes provide additional insights into potential predator–prey interactions. Ciliates, followed by dinoflagellates, Syndiniales, rhizaria, and stramenopiles, dominated the vent protistan community and included bacterivorous species, species known to host symbionts, and parasites. Our findings provide an estimate of protistan grazing pressure within hydrothermal vent food webs, highlighting the important role that diverse protistan communities play in deep-sea carbon cycling.
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Noda, Satoko, Moriya Ohkuma, Akinori Yamada, Yuichi Hongoh, and Toshiaki Kudo. "Phylogenetic Position and In Situ Identification of Ectosymbiotic Spirochetes on Protists in the Termite Gut." Applied and Environmental Microbiology 69, no. 1 (January 2003): 625–33. http://dx.doi.org/10.1128/aem.69.1.625-633.2003.
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ABSTRACT Phylogenetic relationships, diversity, and in situ identification of spirochetes in the gut of the termite Neotermes koshunensis were examined without cultivation, with an emphasis on ectosymbionts attached to flagellated protists. Spirochetes in the gut microbial community investigated so far are related to the genus Treponema and divided into two phylogenetic clusters. In situ hybridizations with a 16S rRNA-targeting consensus oligonucleotide probe for one cluster (known as termite Treponema cluster I) detected both the ectosymbiotic spirochetes on gut protists and the free-swimming spirochetes in the gut fluid of N. koshunensis. The probe for the other cluster (cluster II), which has been identified as ectosymbionts on gut protists of two other termite species, Reticulitermes speratus and Hodotermopsis sjoestedti, failed to detect any spirochete population. The absence of cluster II spirochetes in N. koshunensis was confirmed by intensive 16S ribosomal DNA (rDNA) clone analysis, in which remarkably diverse spirochetes of 45 phylotypes were identified, almost all belonging to cluster I. Ectosymbiotic spirochetes of the three gut protist species Devescovina sp., Stephanonympha sp., and Oxymonas sp. in N. koshunensis were identified by their 16S rDNA and by in situ hybridizations using specific probes. The probes specific for these ectosymbionts did not receive a signal from the free-swimming spirochetes. The ectosymbionts were dispersed in cluster I of the phylogeny, and they formed distinct phylogenetic lineages, suggesting multiple origins of the spirochete attachment. Each single protist cell harbored multiple spirochete species, and some of the spirochetes were common among protist species. The results indicate complex relationships of the ectosymbiotic spirochetes with the gut protists.
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Allen, R., TC Summerfield, K. Currie, PW Dillingham, and LJ Hoffmann. "Distinct processes structure bacterioplankton and protist communities across an oceanic front." Aquatic Microbial Ecology 85 (August 6, 2020): 19–34. http://dx.doi.org/10.3354/ame01938.
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Bacterioplankton and protists fulfil key roles in marine ecosystems. Understanding the abundance and distribution of these organisms through space and time is a central focus of biological oceanographers. The role of oceanographic features, in addition to environmental conditions, in structuring bacterioplankton and protist communities has been increasingly recognised. We investigated patterns in bacterioplankton and protist diversity and community structure across the Southland Front system, a compaction of the subtropical front zone, to the east of New Zealand’s South Island. We collected 24 seawater samples across a ~65 km transect and characterised bacterioplankton and protist community composition using high-throughput sequencing of the 16S and 18S rRNA genes, respectively. We identified frontal waters as a bacterioplankton diversity hotspot relative to neighbouring subtropical and subantarctic waters, but did not find evidence of this effect in protists. Bacterioplankton showed pronounced spatial structuring across the front, with communities closely tracking water type through the region. Protist communities also tracked water type through the region, though this effect was substantially less pronounced. We used an ecological null model approach to demonstrate that protist communities are primarily assembled through stochastic processes, whilst bacterioplankton are primarily assembled through deterministic processes across the Southland Front system. We suggest that this divergence emerges from fundamental differences in the characteristics of bacterioplankton and protist communities. Our findings add to a growing body of literature highlighting the importance of oceanographic features in shaping bacterioplankton and protist communities, promoting the necessity for such features to be considered more explicitly in the future.
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Murase, Jun, Matthias Noll, and Peter Frenzel. "Impact of Protists on the Activity and Structure of the Bacterial Community in a Rice Field Soil." Applied and Environmental Microbiology 72, no. 8 (August 2006): 5436–44. http://dx.doi.org/10.1128/aem.00207-06.
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ABSTRACT Flooded rice fields have become a model system for the study of soil microbial ecology. In Italian rice fields, in particular, aspects from biogeochemistry to molecular ecology have been studied, but the impact of protistan grazing on the structure and function of the prokaryotic community has not been examined yet. We compared an untreated control soil with a γ-radiation-sterilized soil that had been reinoculated with a natural bacterial assemblage. In order to verify that the observed effects were due to protistan grazing and did not result from sterilization, we set up a third set of microcosms containing sterilized soil that had been reinoculated with natural assemblage bacteria plus protists. The spatial and temporal changes in the protistan and prokaryotic communities were examined by denaturing gradient gel electrophoresis (DGGE) and terminal restriction fragment length polymorphism (T-RFLP) analysis, respectively, both based on the small-subunit gene. Sequences retrieved from DGGE bands were preferentially affiliated with Cercozoa and other bacteriovorous flagellates. Without protists, the level of total DNA increased with incubation time, indicating that the level of the microbial biomass was elevated. Betaproteobacteria were preferentially preyed upon, while low-G+C-content gram-positive bacteria became more dominant under grazing pressure. The bacterial diversity detectable by T-RFLP analysis was greater in the presence of protists. The level of extractable NH4 + was lower and the level of extractable SO4 2− was higher without protists, indicating that nitrogen mineralization and SO4 2− reduction were stimulated by protists. Most of these effects were more obvious in the partially oxic surface layer (0 to 3 mm), but they could also be detected in the anoxic subsurface layer (10 to 13 mm). Our observations fit well into the overall framework developed for protistan grazing, but with some modifications pertinent to the wetland situation: O2 was a major control, and O2 availability may have limited directly and indirectly the development of protists. Although detectable in the lower anoxic layer, grazing effects were much more obvious in the partially oxic surface layer.
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WEEDALL, GARETH D., and NEIL HALL. "Sexual reproduction and genetic exchange in parasitic protists." Parasitology 142, S1 (December 22, 2014): S120—S127. http://dx.doi.org/10.1017/s0031182014001693.
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SUMMARYA key part of the life cycle of an organism is reproduction. For a number of important protist parasites that cause human and animal disease, their sexuality has been a topic of debate for many years. Traditionally, protists were considered to be primitive relatives of the ‘higher’ eukaryotes, which may have diverged prior to the evolution of sex and to reproduce by binary fission. More recent views of eukaryotic evolution suggest that sex, and meiosis, evolved early, possibly in the common ancestor of all eukaryotes. However, detecting sex in these parasites is not straightforward. Recent advances, particularly in genome sequencing technology, have allowed new insights into parasite reproduction. Here, we review the evidence on reproduction in parasitic protists. We discuss protist reproduction in the light of parasitic life cycles and routes of transmission among hosts.
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Jousset, Alexandre, Enrique Lara, Luis G. Wall, and Claudio Valverde. "Secondary Metabolites Help Biocontrol Strain Pseudomonas fluorescens CHA0 To Escape Protozoan Grazing." Applied and Environmental Microbiology 72, no. 11 (November 2006): 7083–90. http://dx.doi.org/10.1128/aem.00557-06.
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ABSTRACT In soil ecosystems, bacteria must cope with predation activity, which is attributed mainly to protists. The development of antipredation strategies may help bacteria maintain higher populations and persist longer in the soil. We analyzed the interaction between the root-colonizing and biocontrol strain Pseudomonas fluorescens CHA0 and three different protist isolates (an amoeba, a flagellate, and a ciliate). CHA0 produces a set of antibiotics, HCN, and an exoprotease. We observed that protists cannot grow on CHA0 but can multiply on isogenic regulatory mutants that do not produce the extracellular metabolites. The in vitro responses to CHA0 cells and its exoproducts included growth inhibition, encystation, paralysis, and cell lysis. By analyzing the responses of protists to bacterial supernatants obtained from different isogenic mutants whose production of one or more exometabolites was affected and also to culture extracts with antibiotic enrichment, we observed different contributions of the phenolic antifungal compound 2,4-diacetylphloroglucinol (DAPG) and the extracellular protease AprA to CHA0 toxicity for protists and to the encystation-reactivation cycle. The grazing pressure artificially produced by a mixture of the three protists in a microcosm system resulted in reduced colonization of cucumber roots by a regulatory isogenic CHA0 mutant unable to produce toxins. These results suggest that exometabolite production in biocontrol strain CHA0 may contribute to avoidance of protist grazing and help sustain higher populations in the rhizosphere, which may be a desirable and advantageous trait for competition with other bacteria for available resources.
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Mignot, Par J. P., and A. Molina. "Etude ultrastructurale de Protoopalina saturnalis (Léger et Duboscq 1904) Metcalf 1918, protiste parasite du poisson marin Box boops L." Archiv für Protistenkunde 135, no. 1-4 (January 1988): 255–70. http://dx.doi.org/10.1016/s0003-9365(88)80074-5.
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Cunningham, Joseph J., Nancy E. Kinner, and Maureen Lewis. "Protistan Predation Affects Trichloroethene Biodegradation in a Bedrock Aquifer." Applied and Environmental Microbiology 75, no. 24 (October 9, 2009): 7588–93. http://dx.doi.org/10.1128/aem.01820-09.
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ABSTRACT Despite extensive research on the bottom-up force of resource availability (e.g., electron donors and acceptors), slow biodegradation rates and stalling at cis-dichloroethene (cDCE) and vinyl chloride continue to be observed in aquifers contaminated with trichloroethene (TCE). The objective of this research was to gauge the impact of the top-down force of protistan predation on TCE biodegradation in laboratory microcosms. When indigenous bacteria from an electron donor-limited TCE-contaminated bedrock aquifer were present, the indigenous protists inhibited reductive dechlorination altogether. The presence of protists during organic carbon-amended conditions caused the bacteria to elongate (length:width, ≥10:1), but reductive dechlorination was still inhibited. When a commercially available dechlorinating bacterial culture and an organic carbon amendment were added in he presence of protists, the elongated bacteria predominated and reductive dechlorination stalled at cDCE. When protists were removed under organic carbon-amended conditions, reductive dechlorination stalled at cDCE, whereas in the presence organic carbon and bacterial amendments, the total chlorinated ethene concentration decreased, indicating TCE was converted to ethene and/or CO2. The data suggested that indigenous protists grazed dechlorinators to extremely low levels, inhibiting dechlorination altogether. Hence, in situ bioremediation/bioaugmentation may not be successful in mineralizing TCE unless the top-down force of protistan predation is inhibited.
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Kuppardt, Steffen, Antonis Chatzinotas, and Matthias Kästner. "Development of a Fatty Acid and RNA Stable Isotope Probing-Based Method for Tracking Protist Grazing on Bacteria in Wastewater." Applied and Environmental Microbiology 76, no. 24 (October 29, 2010): 8222–30. http://dx.doi.org/10.1128/aem.01632-10.
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ABSTRACT Removal of potential pathogenic bacteria, for example, during wastewater treatment, is effected by sorption, filtration, natural die-off, lysis by viruses, and grazing by protists, but the actual contribution of grazing has never been assessed quantitatively. A methodical approach for analyzing the grazing of protists on 13C-labeled prey bacteria was developed which enables mass balances of the carbon turnover to be drawn, including yield estimation. Model experiments for validating the approach were performed in closed microcosms with the ciliate Uronema sp. and 13C-labeled Escherichia coli as model prey. The transfer of bacterial 13C into grazing protist biomass was investigated by fatty acid (FA) and RNA stable isotope probing (SIP). Uronema sp. showed ingestion rates of ∼390 bacteria protist−1 h−1, and the temporal patterns of 13C assimilation from the prey bacteria to the protist FA were identified. Nine fatty acids specific for Uronema sp. were found (20:0, i20:0, 22:0, 24:0, 20:1ω9c, 20:1ω9t, 22:1ω9c, 22:1ω9t, and 24:1). Four of these fatty acids (22:0, 20:1ω9t, 22:1ω9c, and 22:1ω9t) were enriched very rapidly after 3 h, indicating grazing on bacteria without concomitant cell division. Other fatty acids (20:0, i20:0, and 20:1ω9c) were found to be indicative of growth with cell division. The fatty acids were found to be labeled with a percentage of labeled carbon (atoms percent [atom%]) up to 50. Eighteen percent of the E. coli-derived 13C was incorporated into Uronema biomass, whereas 11% was mineralized. Around 5 mol bacterial carbon was necessary in order to produce 1 mol protist carbon (yx / s ≈ 0.2), and the temporal pattern of 13C labeling of protist rRNA was also shown. A consumption of around 1,000 prey bacteria (∼98 atom% 13C) per protist cell appears to be sufficient to provide detectable amounts of label in the protist RNA. The large shift in the buoyant density fraction of 13C-labeled protist RNA demonstrated a high incorporation of 13C, and reverse transcription-real-time PCR (RT-qPCR) confirmed that protist rRNA increasingly dominated in the heavy RNA fraction.
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Li, Ran, Chen Hu, Jianning Wang, Jun Sun, Ying Wang, Nianzhi Jiao, and Dapeng Xu. "Biogeographical Distribution and Community Assembly of Active Protistan Assemblages along an Estuary to a Basin Transect of the Northern South China Sea." Microorganisms 9, no. 2 (February 10, 2021): 351. http://dx.doi.org/10.3390/microorganisms9020351.
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Marine protists are essential for globally critical biological processes, including the biogeochemical cycles of matter and energy. However, compared with their prokaryotic counterpart, it remains largely unclear how environmental factors determine the diversity and distribution of the active protistan communities on the regional scale. In the present study, the biodiversity, community composition, and potential drivers of the total, abundant, and rare protistan groups were studied using high throughput sequencing on the V9 hyper-variable regions of the small subunit ribosomal RNA (SSU rRNA) along an estuary to basin transect in the northern South China Sea. Overall, Bacillariophyta and Cercozoa were abundant in the surface water; heterotrophic protists including Spirotrichea and marine stramenopiles 3 (MAST-3) were more abundant in the subsurface waters near the heavily urbanized Pearl River estuary; Chlorophyta and Pelagophyceae were abundant at the deep chlorophyll maximum depth, while Hacrobia, Radiolaria, and Excavata were the abundant groups in the deep water. Salinity, followed by water depth, temperature, and other biological factors, were the primary factors controlling the distinct vertical and horizontal distribution of the total and abundant protists. Rare taxa were driven by water depth, followed by temperature, salinity, and the concentrations of PO43−. The active protistan communities were mainly driven by dispersal limitation, followed by drift and other ecological processes.
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Nowack, Eva C. M., and Michael Melkonian. "Endosymbiotic associations within protists." Philosophical Transactions of the Royal Society B: Biological Sciences 365, no. 1541 (March 12, 2010): 699–712. http://dx.doi.org/10.1098/rstb.2009.0188.
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The establishment of an endosymbiotic relationship typically seems to be driven through complementation of the host's limited metabolic capabilities by the biochemical versatility of the endosymbiont. The most significant examples of endosymbiosis are represented by the endosymbiotic acquisition of plastids and mitochondria, introducing photosynthesis and respiration to eukaryotes. However, there are numerous other endosymbioses that evolved more recently and repeatedly across the tree of life. Recent advances in genome sequencing technology have led to a better understanding of the physiological basis of many endosymbiotic associations. This review focuses on endosymbionts in protists (unicellular eukaryotes). Selected examples illustrate the incorporation of various new biochemical functions, such as photosynthesis, nitrogen fixation and recycling, and methanogenesis, into protist hosts by prokaryotic endosymbionts. Furthermore, photosynthetic eukaryotic endosymbionts display a great diversity of modes of integration into different protist hosts. In conclusion, endosymbiosis seems to represent a general evolutionary strategy of protists to acquire novel biochemical functions and is thus an important source of genetic innovation.
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Nayduch, Dana. "Temporal Progression of Herpetomonas muscarum Leidy (Kinetoplastida: Trypanosomatidae) in the Midgut of Musca domestica L. (Diptera: Muscidae)." Journal of Entomological Science 44, no. 2 (April 1, 2009): 141–48. http://dx.doi.org/10.18474/0749-8004-44.2.141.
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Herpetomonas muscarum Leidy (Kinetoplastida: Trypanosomatidae) is a protistan symbiont that colonizes the hindgut of the housefly, Musca domestica L. (Diptera: Muscidae). The temporal location and transition of this symbiont within the fly has been understudied. In this study, the progression of Herpetomonas within the mid and hindgut with reference to the peritrophic matrix (PM) was examined microscopically and was compared with the fate of a bacterium (GFP-tagged E. coli). The housefly PM is a double-layered, open-ended physical barrier that separates ingested substances from the midgut epithelium and terminates near the hindgut. In the midgut, bacteria were confined within the inner PM, lysed by digestive enzymes, and compacted into fecal pellets within 12 h. In contrast, Herpetomonas initially resided within the inner PM, but many protists moved to the interPM space within a few hours. Additionally, protists rapidly progressed to the open end of the PM at the midgut/hindgut junction, in as little as 4–6 h postingestion, entering the ectoperitrophic space and attaching to the hindgut epithelium. Unlike bacteria, Herpetomonas demonstrated a hastened progression to the hindgut and avoided being immobilized, lysed and enclosed in a fecal pellet by the inner PM. Thus, whereas flies do not have permanent bacterial “flora” (because bacteria cannot escape the PM and are trapped and lysed), this protist has found a way to circumvent this fate and establish as a permanent hindgut symbiont. These results have applicable relevance to human-parasitic trypanosomatids that use stercorarian (posterior station) transmission from vectoring insects, such as Trypanosoma cruzi Chagas in triatomine bugs.
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Collier, Jackie L., and Joshua S. Rest. "Swimming, gliding, and rolling toward the mainstream: cell biology of marine protists." Molecular Biology of the Cell 30, no. 11 (May 15, 2019): 1245–48. http://dx.doi.org/10.1091/mbc.e18-11-0724.
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Marine protists are a polyphyletic group of organisms playing major roles in the ecology and biogeochemistry of the oceans, including performing much of Earth’s photosynthesis and driving the carbon, nitrogen, and silicon cycles. In addition, marine protists occupy key positions in the tree of life, including as the closest relatives of metazoans. Despite all the reasons to better understand them, knowledge of the cell biology of most marine protist lineages is sparse. This is beginning to change thanks to vibrant growth in the development of new model organisms. Here, we survey some recent advances in studying the cell biology of marine protists toward understanding the functional basis of their unique features, gaining new perspectives on universal eukaryotic biology, and for understanding homologous biology within metazoans and the evolution of metazoan traits.
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Gast, Rebecca J., Mark R. Dennett, and David A. Caron. "Characterization of Protistan Assemblages in the Ross Sea, Antarctica, by Denaturing Gradient Gel Electrophoresis." Applied and Environmental Microbiology 70, no. 4 (April 2004): 2028–37. http://dx.doi.org/10.1128/aem.70.4.2028-2037.2004.
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ABSTRACT The diversity of protistan assemblages has traditionally been studied using microscopy and morphological characterization, but these methods are often inadequate for ecological studies of these communities because most small protists inherently lack adequate taxonomic characters to facilitate their identification at the species level and many protistan species also do not preserve well. We have therefore used a culture-independent approach (denaturing gradient gel electrophoresis [DGGE]) to obtain an assessment of the genetic composition and distribution of protists within different microhabitats (seawater, meltwater or slush on sea-ice floes, and ice) of the Ross Sea, Antarctica. Samples of the same type (e.g., water) shared more of the same bands than samples of different types (e.g., ice versus water), despite being collected from different sites. These findings imply that samples from the same environment have a similar protistan species composition and that the type of microenvironment significantly influences the protistan species composition of these Antarctic assemblages. It should be noted that a large number of bands among the samples within each microhabitat were distinct, indicating the potential presence of significant genetic diversity within each microenvironment. Sequence analysis of selected DGGE bands revealed sequences that represent diatoms, dinoflagellates, ciliates, flagellates, and several unidentified eukaryotes.
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Thomas, Matthew C., L. Brent Selinger, and G. Douglas Inglis. "Seasonal Diversity of Planktonic Protists in Southwestern Alberta Rivers over a 1-Year Period as Revealed by Terminal Restriction Fragment Length Polymorphism and 18S rRNA Gene Library Analyses." Applied and Environmental Microbiology 78, no. 16 (June 8, 2012): 5653–60. http://dx.doi.org/10.1128/aem.00237-12.
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ABSTRACTThe temporal dynamics of planktonic protists in river water have received limited attention despite their ecological significance and recent studies linking phagotrophic protists to the persistence of human-pathogenic bacteria. Using molecular-based techniques targeting the 18S rRNA gene, we studied the seasonal diversity of planktonic protists in Southwestern Alberta rivers (Oldman River Basin) over a 1-year period. Nonmetric multidimensional scaling analysis of terminal restriction fragment length polymorphism (T-RFLP) data revealed distinct shifts in protistan community profiles that corresponded to season rather than geographical location. Community structures were examined by using clone library analysis; HaeIII restriction profiles of 18S rRNA gene amplicons were used to remove prevalent solanaceous plant clones prior to sequencing. Sanger sequencing of the V1-to-V3 region of the 18S rRNA gene libraries from spring, summer, fall, and winter supported the T-RFLP results and showed marked seasonal differences in the protistan community structure. The spring library was dominated by Chloroplastidae (29.8%), Centrohelida (28.1%), and Alveolata (25.5%), while the summer and fall libraries contained primarily fungal clones (83.0% and 88.0%, respectively). Alveolata (35.6%), Euglenozoa (24.4%), Chloroplastida (15.6%), and Fungi (15.6%) dominated the winter library. These data demonstrate that planktonic protists, including protozoa, are abundant in river water in Southwestern Alberta and that conspicuous seasonal shifts occur in the community structure.
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Majda, Stephan, Jens Boenigk, and Daniela Beisser. "Intraspecific Variation in Protists: Clues for Microevolution from Poteriospumella lacustris (Chrysophyceae)." Genome Biology and Evolution 11, no. 9 (August 6, 2019): 2492–504. http://dx.doi.org/10.1093/gbe/evz171.
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Abstract Species delimitation in protists is still a challenge, attributable to the fact that protists are small, difficult to observe and many taxa are poor in morphological characters, whereas most current phylogenetic approaches only use few marker genes to measure genetic diversity. To address this problem, we assess genome-level divergence and microevolution in strains of the protist Poteriospumella lacustris, one of the first free-living, nonmodel organisms to study genome-wide intraspecific variation. Poteriospumella lacustris is a freshwater protist belonging to the Chrysophyceae with an assumed worldwide distribution. We examined three strains from different geographic regions (New Zealand, China, and Austria) by sequencing their genomes with the Illumina and PacBio platforms. The assembled genomes were small with 49–55 Mb but gene-rich with 16,000–19,000 genes, of which ∼8,000 genes could be assigned to functional categories. At least 68% of these genes were shared by all three species. Genetic variation occurred predominantly in genes presumably involved in ecological niche adaptation. Most surprisingly, we detected differences in genome ploidy between the strains (diploidy, triploidy, and tetraploidy). In analyzing intraspecific variation, several mechanisms of diversification were identified including SNPs, change of ploidy and genome size reduction.
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González, Juan M. "Bacterivory Rate Estimates and Fraction of Active Bacterivores in Natural Protist Assemblages from Aquatic Systems." Applied and Environmental Microbiology 65, no. 4 (April 1, 1999): 1463–69. http://dx.doi.org/10.1128/aem.65.4.1463-1469.1999.
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ABSTRACT Unlike the fraction of active bacterioplankton, the fraction of active bacterivores (i.e., those involved in grazing) during a specified time period has not been studied yet. Fractions of protists actively involved in bacterivory were estimated assuming that the distributions of bacteria and fluorescently labeled bacteria (FLB) ingested by protists follow Poisson distributions. Estimates were compared with experimental data obtained from FLB uptake experiments. The percentages of protists with ingested FLB (experimental) and the estimates obtained from Poisson distributions were similar for both flagellates and ciliates. Thus, the fraction of protists actively grazing on natural bacteria during a given time period could be estimated. The fraction of protists with ingested bacteria depends on the incubation time and reaches a saturating value. Aquatic systems with very different characteristics were analyzed; estimates of the fraction of protists actively grazing on bacteria ranged from 7 to 100% in the studied samples. Some nanoflagellates appeared to be grazing on specific bacterial sizes. Evidence indicated that there was no discrimination for or against bacterial surrogates (i.e., FLB); also, bacteria were randomly encountered by bacterivorous protists during these short-term uptake experiments. These analyses made it possible to estimate the ingestion rates from FLB uptake experiments by counting the number of flagellates containing ingested FLB. These results represent the first reported estimates of active bacterivores in natural aquatic systems; also, a proposed protocol for estimating in situ ingestion rates by protists represents a significant improvement and simplification to the current protocol and avoids the tedious work of counting the number of ingested FLB per protist.
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Levin, Lisa A., Andrew J. Gooday, and David W. James. "Dressing up for the deep: agglutinated protists adorn an irregular urchin." Journal of the Marine Biological Association of the United Kingdom 81, no. 5 (October 2001): 881–82. http://dx.doi.org/10.1017/s0025315401004738.
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A specimen of the deep-water, spatangoid urchin, Cystochinus loveni, wearing a costume of agglutinated protists, was collected from 3088 m in the Gulf of Alaska, north-east Pacific. Over 24 putative taxa of living and dead foraminiferans and xenophyophores, as well as a sipunculan, polychaete, tanaid, and two isopods, were collected from the dorsal surface of this single individual. This is the first report of a deep-sea urchin using rhizopod protists and it is proposed that the urchin acquires camouflage or benefits from increased specific gravity associated with the protistan cloak.
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Li, Wei, Mircea Podar, and Rachael M. Morgan-Kiss. "Ultrastructural and Single-Cell-Level Characterization Reveals Metabolic Versatility in a Microbial Eukaryote Community from an Ice-Covered Antarctic Lake." Applied and Environmental Microbiology 82, no. 12 (April 15, 2016): 3659–70. http://dx.doi.org/10.1128/aem.00478-16.
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ABSTRACTThe McMurdo Dry Valleys (MCM) of southern Victoria Land, Antarctica, harbor numerous ice-covered bodies of water that provide year-round liquid water oases for isolated food webs dominated by the microbial loop. Single-cell microbial eukaryotes (protists) occupy major trophic positions within this truncated food web, ranging from primary producers (e.g., chlorophytes, haptophytes, and cryptophytes) to tertiary predators (e.g., ciliates, dinoflagellates, and choanoflagellates). To advance the understanding of MCM protist ecology and the roles of MCM protists in nutrient and energy cycling, we investigated potential metabolic strategies and microbial interactions of key MCM protists isolated from a well-described lake (Lake Bonney). Fluorescence-activated cell sorting (FACS) of enrichment cultures, combined with single amplified genome/amplicon sequencing and fluorescence microscopy, revealed that MCM protists possess diverse potential metabolic capabilities and interactions. Two metabolically distinct bacterial clades (FlavobacteriaandMethylobacteriaceae) were independently associated with two key MCM lake microalgae (IsochrysisandChlamydomonas, respectively). We also report on the discovery of two heterotrophic nanoflagellates belonging to the Stramenopila supergroup, one of which lives as a parasite ofChlamydomonas, a dominate primary producer in the shallow, nutrient-poor layers of the lake.IMPORTANCESingle-cell eukaryotes called protists play critical roles in the cycling of organic matter in aquatic environments. In the ice-covered lakes of Antarctica, protists play key roles in the aquatic food web, providing the majority of organic carbon to the rest of the food web (photosynthetic protists) and acting as the major consumers at the top of the food web (predatory protists). In this study, we utilized a combination of techniques (microscopy, cell sorting, and genomic analysis) to describe the trophic abilities of Antarctic lake protists and their potential interactions with other microbes. Our work reveals that Antarctic lake protists rely on metabolic versatility for their energy and nutrient requirements in this unique and isolated environment.
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Patterson, David J., Kari Nygaard, Gero Steinberg, and Carol M. Turley. "Heterotrophic flagellates and other protists associated with oceanic detritus throughout the water column in the mid North Atlantic." Journal of the Marine Biological Association of the United Kingdom 73, no. 1 (February 1993): 67–95. http://dx.doi.org/10.1017/s0025315400032653.
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Heterotrophic protists, mostly flagellates, encountered in association with marine detritus from various collections in the mid North Atlantic are described. About 40 species have been identified and are reported. Taxa reported here for the first time are: Caecitellus gen. nov. (Protista incertae sedis) and Ministeria marisola gen. nov., sp. nov. (Protista incertae sedis). The flagellates form a subset of the community of heterotrophic marine flagellates encountered in more productive marine sites. Most species are bacterivorous and small. The community extends to the ocean floor but the diversity is reduced in samples taken from greater depths. The decline in species diversity is linked also to a decline in numbers of individuals. We discuss these changes in relation to food supply and pressure effects.
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Metfies, Katja, Friedhelm Schroeder, Johanna Hessel, Jochen Wollschläger, Sebastian Micheller, Christian Wolf, Estelle Kilias, et al. "High-resolution monitoring of marine protists based on an observation strategy integrating automated on-board filtration and molecular analyses." Ocean Science 12, no. 6 (November 22, 2016): 1237–47. http://dx.doi.org/10.5194/os-12-1237-2016.
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Abstract. Information on recent biomass distribution and biogeography of photosynthetic marine protists with adequate temporal and spatial resolution is urgently needed to better understand the consequences of environmental change for marine ecosystems. Here we introduce and review a molecular-based observation strategy for high-resolution assessment of these protists in space and time. It is the result of extensive technology developments, adaptations and evaluations which are documented in a number of different publications, and the results of the recently completed field testing which are introduced in this paper. The observation strategy is organized at four different levels. At level 1, samples are collected at high spatiotemporal resolution using the remotely controlled automated filtration system AUTOFIM. Resulting samples can either be preserved for later laboratory analyses, or directly subjected to molecular surveillance of key species aboard the ship via an automated biosensor system or quantitative polymerase chain reaction (level 2). Preserved samples are analyzed at the next observational levels in the laboratory (levels 3 and 4). At level 3 this involves molecular fingerprinting methods for a quick and reliable overview of differences in protist community composition. Finally, selected samples can be used to generate a detailed analysis of taxonomic protist composition via the latest next generation sequencing technology (NGS) at level 4. An overall integrated dataset of the results based on the different analyses provides comprehensive information on the diversity and biogeography of protists, including all related size classes. At the same time the cost of the observation is optimized with respect to analysis effort and time.
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Putri, Rossanita Truelovin Hadi, Raharjo Raharjo, and Fida Racmadiarti. "Practicing creative thinking skills: Inquiry base activity sheets development in protists learning material." JPBIO (Jurnal Pendidikan Biologi) 6, no. 1 (April 29, 2021): 1–11. http://dx.doi.org/10.31932/jpbio.v6i1.847.
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Protist learning materials have been developed by many researchers, but no one has developed learning tools by training students' creative thinking skills. This study aims to produce LKPD based inquiry on protist material and to train creative thinking skills, by describing the validity and effectiveness of LKPD on protist material. The LKPD developed refers to the 4D model which consists of the stages of define, design, develop, and disseminate. The research design used was the One-Group Pretest-Posttest Design. LKPD was tried out on 12 students of class XI MIPA SMA. After using LKPD, the validity and effectiveness data were analyzed descriptively quantitatively. The validity of the LKPD is measured based on the assessment of the education expert lecturers and materials. The effectiveness of protist LKPD is measured based on the learning outcomes of students and students' responses. The results showed the validity of the LKPD was 99.4% with the very valid category. The effectiveness based on the learning outcomes of students was 92% with the category very effective and the response of students was 99%. Based on the results of this assessment, it can be concluded that LKPD based on the inquiry on protist material to train creative thinking skills is declared valid and effective.Keywords: Activity sheets, inquiry learning, creative thinking, protists
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Xu, Henglong, Weibo Song, Alan Warren, Khaled A. S. Al-Rasheid, Saleh A. Al-Farraj, Jun Gong, and Xiaozhong Hu. "Planktonic protist communities in a semi-enclosed mariculture pond: structural variation and correlation with environmental conditions." Journal of the Marine Biological Association of the United Kingdom 88, no. 7 (July 22, 2008): 1353–62. http://dx.doi.org/10.1017/s0025315408002129.
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In order to evaluate the environmental status within a mariculture pond, temporal variations of physico-chemical factors, protist community structure and interactions between biota and environmental conditions were investigated during a complete cycle in semi-enclosed shrimp-farming waters near Qingdao, north China. Results revealed that: (1) a total of 54 protist taxa with ten dominant species was present, comprising 4 chlorophyceans, 2 chrysophyceans, 5 cryptophyceans, 10 dinoflagellates, 3 euglenophyceans, 10 diatoms, 18 ciliates and 2 sarcodines; (2) a single peak of protist abundance occurred in October, mainly due to the chlorophyceans, diatoms and chrysophyceans, while the bimodal peaks of biomass in July and October were mainly due to the ciliates, dinoflagellates and diatoms; (3) the succession of protist communities significantly correlated with the changes of nutrients, salinity and temperature, especially phosphate, either alone or in combination with NO3; (4) species diversity and evenness indices were found to be relatively independent of physico-chemical factors, whereas species richness and the ratio of biomass to abundance were strongly correlated with water temperature and abundances of bacteria. It was concluded that planktonic protists are potentially useful bioindicators of water quality in a semi-enclosed mariculture system.
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Yunanda, Intan, Herawati Susilo, and Abdul Ghofur. "Misconceptions identification on biodiversity and protist using multiple choice open reason (mcor)." Biosfer 12, no. 2 (November 18, 2019): 170–81. http://dx.doi.org/10.21009/biosferjpb.v12n2.170-181.
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This research aims to identify misconceptions of Biodiversity and Protist material. This type of research is a quantitative descriptive study. The sampling technique is purposive sampling with the provisions that misconceptions have not been identified, and students have received Biodiversity and protists. The object of the research is the students of class XI SMA Islam Malang, SMAN 1 Trenggalek, MAN 2 Lamongan, and SMAN 1 Pare, each in one class with a total of 127 students. Retrieval of data using a diagnostic instrument in the form of multiple-choice open reason (MCOR) with a total of 15 questions about Biodiversity and 15 questions about Protist. The results showed the average of misconceptions of 22,08% experienced by students on Biodiversity and the mean of misconceptions of 13,25% experienced by students on Protist. The highest misconception occurred in the threat indicator of biodiversity damage that is equal to 35,91%. Whereas for Protist, the highest misconception occurred in the sub-indicator identification of the general characteristics of Protist like an animal that is 26,28%. The conclusion is the misconception on the material of Biodiversity and Protist, including misconception type 2 or Mi-2, that is, students answer incorrectly to the core questions and are accompanied by the right reasons. A suggestion from the research that has been done is that it is necessary to develop a level three diagnostic instrument used by experts to find out students' misconceptions so that the results are more detailed. Besides, it is necessary to identify the causes of misconceptions and identify misconceptions in student handbooks on Biodiversity and Protist.
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Stoecker, Diane K., Mary Putt, and Tiffany Moisan. "Nano- and Microplankton Dynamics during the Spring Phaeocystis Sp. Bloom in McMurdo Sound, Antarctica." Journal of the Marine Biological Association of the United Kingdom 75, no. 4 (November 1995): 815–32. http://dx.doi.org/10.1017/s0025315400038170.
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The seasonal development of the microbial food web in eastern McMurdo Sound, Antarctica, was investigated during and immediately after the 1990–1991 bloom of Phaeocystis sp. (Prymnesiophyceae: Prymnesiales). From 23 November to 7 December, which was before the appearance of macroscopic colonies of Phaeocystis, both phytoplankton and Protozoa were low in abundance. During the Phaeocystis bloom (~10 December to 7 January), phytoplankton biomass was high and was dominated by colonial and singlecelled Phaeocystis, but other phytoplankton taxa, including diatoms and photosynthetic dinoflagellates, co-occurred. Heterotrophic nanoplankton and protozoan microzooplankton increased dramatically in biomass during the bloom. Non-thecate heterotrophic dinoflagellates were the most abundant microzooplankters. There was no evidence for inhibition of the microbial food web by Phaeocystis. By the post-bloom period, macroscopic colonies were rare and phytoplankton biomass had declined markedly. Microzooplankton biomass continued to rise until the end of the sampling period (23 January). Microfaecal pellets (median size range, 10–30 μm) were abundant during the bloom and post-bloom periods. In the post-bloom period, the heterotrophic protistan assemblage became very diverse, with numerous trophic linkages within the microbial food web. The abundance and diversity of the heterotrophic protist assemblage suggests that there was little control of protists by metazoans and that the microbial food web, consisting of bacteria, algae and Protozoa, was poorly coupled to metazoan zooplankton.
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Hwang, S. J., and R. T. Heath. "Bacterial productivity and protistan bacterivory in coastal and offshore communities of Lake Erie." Canadian Journal of Fisheries and Aquatic Sciences 54, no. 4 (April 1, 1997): 788–99. http://dx.doi.org/10.1139/f96-345.
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The importance of protists as bacterivores in a coastal community and an offshore community of Lake Erie was compared during the summer of 1994. Bacterial density, cell size, and empirical conversion factors for bacterial productivity were highly variable at both sites and greater at the coastal site (P < 0.01). Bacterial productivity at the coastal site was 25-50 times higher than at the offshore site. Bacterivory was estimated in situ by fluorescently labeled native bacteria. Per-cell grazing rate and filtering rate for each taxon were routinely determined. Heterotrophic nanoflagellates (HNAN) were the most important protistan bacterivores at the offshore site, while HNAN and ciliates were similarly dominant bacterivores at the coastal site. Mixotrophic bacterivory was important only at the offshore site where Dinobryon was the dominant bacterivore. Bacterial carbon flux through protists was higher at the coastal site by an order of magnitude. Offshore protists grazed virtually the entire bacterial production, while coastal protists usually grazed less than half of the bacterial production. These results suggest that coastal and offshore sites differed fundamentally in the significance of protists to carbon flux through the microbial loop to higher trophic levels.
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Lipps, Jere H. "Major features of protistan evolution: controversies, problems and a few answers." Anuário do Instituto de Geociências 29, no. 1 (January 1, 2006): 55–80. http://dx.doi.org/10.11137/2006_1_55-80.
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The major features of protist evolution are fraught with controversies, problems and few answers, especially in early Earth history. In general they are based on molecular data and fossil evidence that respectively provide a scaffold and details of eukaryotic phylogenetic and ecologic histories. 1. Their origin, inferred from molecular sequences, occurred very early (>;3Ga). They are a chimera of different symbiont-derived organelles, including possibly the nucleus. 2. The initial diversification of eukaryotes may have occurred early in geologic time. Six supergroups exist today, each with fossils known from the Proterozoic and Phanerozoic. 3. Sex, considered an important development, may have been inherited from bacteria. 4. Precambrian protists were largely pelagic cyst-bearing taxa, but benthic forms were probably quite diverse and abundant. 5. Protists gave rise to animals long before 600 Ma through the choanoflagellates, for which no fossil record exists. 6. Acritarchs and skeletonized protists radiated in the Cambrian (544-530 my). From then on, they radiated and became extinct at all the major events recorded in the metazoan fossil record. 7. Protists dominated major environments (shelves and reefs) starting with a significant radiation in the Ordovician, followed by extinctions and other radiations until most died out at the end of the Permian. 8. In the Mesozoic, new planktic protozoa and algae appeared and radiated in pelagic environments. 9. Modern protists are important at all trophic levels in the oceans and a huge number terrestrial, parasitic and symbiotic protists must have existed for much of geologic time as well. 10. The future of protists is likely in jeopardy, just like most reefal, benthic, and planktic metazoans. An urgent need to understand the role of protists in modern threatened oceans should be addressed soon.
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BITENCOURT, JOSÉ A. P., FREDERICO SOBRINHO SILVA, INÁCIO D. DA SILVA-NETO, and MIRIAN A. C. CRAPEZ. "Protists and bacteria interactions in the presence of oil." Anais da Academia Brasileira de Ciências 86, no. 2 (June 2014): 745–54. http://dx.doi.org/10.1590/0001-37652014108012.
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Little is known about the role of protists and bacteria interactions during hydrocarbon biodegradation. This work focused on the effect of oil on protists from three different locations in Guanabara Bay and bacteria from Caulerpa racemosa (BCr), Dictyota menstrualis (BDm) and Laurencia obtusa (BLo) during a 96 h bioassay. Cryptomonadida (site 1, 2 and 3), Scuticociliatida (site 2) and Euplotes sp.1 and Euplotes sp.2 (site 3) appeared after incubation. The highest biomass observed in the controls was as follows: protist site 3 (6.0 µgC.cm–3, 96 h) compared to site 3 with oil (0.7 µgC.cm–3, 96 h); for bacteria, 8.6 µgC.cm–3(BDm, 72 h) and 17.0 µgC.cm–3(BCr with oil, 24 h). After treatment, the highest biomasses were as follows: protists at site 1 and BLo, 6.0 µgC.cm–3 (96 h), compared to site 1 and BLo with oil, 3.31 µgC.cm–3 (96 h); the bacterial biomass was 43.1 µgC.cm–3 at site 2 and BDm (96 h). At site 3 and BLo with oil, the biomass was 18.21 µgC.cm–3 (48 h). The highest biofilm proportions were observed from BCr 1.7 µm (96 h) and BLo with oil 1.8 µm (24 h). BCr, BLo and BDm enhanced biofilm size and reduced the capacity of protists to prey.
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Karlin, Samuel, and Dorit Carmelli. "Codon Signature Extremes In Eukaryote genomes." Israel Journal of Ecology and Evolution 52, no. 3-4 (April 12, 2006): 281–97. http://dx.doi.org/10.1560/ijee_52_3-4_281.
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Twenty-one complete eukaryotic genomes are compared for codon signature biases. The codon signature refers to the dinucleotide relative abundance values at codon sites {1, 2}, {2, 3}, and {3, 4} (4 = 1 of the next codon site). The genomes under study include human, mouse, chicken, three invertebrates, one plant species, eight fungi, and six protists. The dinucleotide CpG is significantly underrepresented at all contiguous codon sites and drastically suppressed in noncoding regions in mammalian species, in yeast-like genomes, in the dicot Arabidopsis thaliana, but not in the filamentous fungi Neurospora crassa and Asperigillus fumigatus, and in the protist Entamoeba histolytica. The dinucleotide TpA, probably due to DNA structural weaknesses, is underrepresented genome-wide and significantly underrepresented in the codon signature for all contiguous codon sites in mammals, inverterbrates, plants, and fungi, but somewhat restricted to codon sites {1, 2} among protists helping in avoidance of stop codons. The amino acid Ser, not of abundance in bacterial genomes, generally ranks among the two most used amino acids among eukaryotes ostensibly resulting from greater activity in the nucleus. The observed differences are linked to specifics of methylation, context-dependent mutation, DNA repair, and replication. For example, the amino acid Leu is broadly abundant in all life domains generally resulting from extra occurrences of the codon TTR, R purine. The malarial protist Plasmodium falciparum shows many codon signature extremes.
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Apple, Jude K., Suzanne L. Strom, Brian Palenik, and Bianca Brahamsha. "Variability in Protist Grazing and Growth on Different Marine Synechococcus Isolates." Applied and Environmental Microbiology 77, no. 9 (March 11, 2011): 3074–84. http://dx.doi.org/10.1128/aem.02241-10.
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ABSTRACTGrazing mortality of the marine phytoplanktonSynechococcusis dominated by planktonic protists, yet rates of consumption and factors regulating grazer-Synechococcusinteractions are poorly understood. One aspect of predator-prey interactions for which little is known are the mechanisms by whichSynechococcusavoids or resists predation and, in turn, how this relates to the ability ofSynechococcusto support growth of protist grazer populations. Grazing experiments conducted with the raptorial dinoflagellateOxyrrhis marinaand phylogenetically diverseSynechococcusisolates (strains WH8102, CC9605, CC9311, and CC9902) revealed marked differences in grazing rates—specifically that WH8102 was grazed at significantly lower rates than all other isolates. Additional experiments using the heterotrophic nanoflagellateGoniomonas pacificaand the filter-feeding tintinnid ciliateEutintinnissp. revealed that this pattern in grazing susceptibility among the isolates transcended feeding guilds and grazer taxon.Synechococcuscell size, elemental ratios, and motility were not able to explain differences in grazing rates, indicating that other features play a primary role in grazing resistance. Growth of heterotrophic protists was poorly coupled to prey ingestion and was influenced by the strain ofSynechococcusbeing consumed. AlthoughSynechococcuswas generally a poor-quality food source, it tended to support higher growth and survival ofG. pacificaandO. marinarelative toEutintinnissp., indicating that suitability ofSynechococcusvaries among grazer taxa and may be a more suitable food source for the smaller protist grazers. This work has developed tractable model systems for further studies of grazer-Synechococcusinteractions in marine microbial food webs.
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Ohkuma, Moriya, Satoko Noda, Satoshi Hattori, Toshiya Iida, Masahiro Yuki, David Starns, Jun-ichi Inoue, Alistair C. Darby, and Yuichi Hongoh. "Acetogenesis from H2plus CO2and nitrogen fixation by an endosymbiotic spirochete of a termite-gut cellulolytic protist." Proceedings of the National Academy of Sciences 112, no. 33 (May 15, 2015): 10224–30. http://dx.doi.org/10.1073/pnas.1423979112.
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Symbiotic associations of cellulolytic eukaryotic protists and diverse bacteria are common in the gut microbial communities of termites. Besides cellulose degradation by the gut protists, reductive acetogenesis from H2plus CO2and nitrogen fixation by gut bacteria play crucial roles in the host termites’ nutrition by contributing to the energy demand of termites and supplying nitrogen poor in their diet, respectively. Fractionation of these activities and the identification of key genes from the gut community of the wood-feeding termiteHodotermopsis sjoestedtirevealed that substantial activities in the gut—nearly 60% of reductive acetogenesis and almost exclusively for nitrogen fixation—were uniquely attributed to the endosymbiotic bacteria of the cellulolytic protist in the genusEucomonympha. The rod-shaped endosymbionts were surprisingly identified as a spirochete species in the genusTreponema, which usually exhibits a characteristic spiral morphology. The endosymbionts likely use H2produced by the protist for these dual functions. Although H2is known to inhibit nitrogen fixation in some bacteria, it seemed to rather stimulate this important mutualistic process. In addition, the single-cell genome analyses revealed the endosymbiont's potentials of the utilization of sugars for its energy requirement, and of the biosynthesis of valuable nutrients such as amino acids from the fixed nitrogen. These metabolic interactions are suitable for the dual functions of the endosymbiont and reconcile its substantial contributions in the gut.
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Finlay, Bland J. "Protist taxonomy: an ecological perspective." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 359, no. 1444 (April 29, 2004): 599–610. http://dx.doi.org/10.1098/rstb.2003.1450.
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This is an exploration of contemporary protist taxonomy within an ecological perspective. As it currently stands, the ‘morphospecies’ does not accommodate the information that might support a truly ecological species concept for the protists. But the ‘morphospecies’ is merely a first step in erecting a taxonomy of the protists, and it is expected to become more meaningful in the light of genetic, physiological and ecological research in the near future. One possible way forward lies in the recognition that sexual and asexual protists may all be subject to forces of cohesion that result in (DNA) sequence–similarity clusters. A starting point would then be the detection of ‘ecotypes’—where genotypic and phenotypic clusters correspond; but for that we need better information regarding the extent of clonality in protists, and better characterization of ecological niches and their boundaries. There is some progress with respect to the latter. Using the example of a community of ciliated protozoa living in the stratified water column of a freshwater pond, it is shown to be possible to gauge the potential of protists to partition their local environment into ecological niches. Around 40 morphospecies can coexist in the superimposed water layers, which presumably represent different ecological niches, but we have yet to discover if these are discrete or continuously variable. It is a myth that taxonomic problems are more severe for protists than for animals and plants. Most of the fundamental problems associated with species concepts (e.g. asexuals, sibling species, phenotypic variation) are distributed across biota in general. The recent history of the status of Pfiesteria provides a model example of an integrated approach to solving what are essentially taxonomic problems.
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Spratt, David M., and Ian Beveridge. "Wildlife parasitology in Australia: past, present and future." Australian Journal of Zoology 66, no. 4 (2018): 286. http://dx.doi.org/10.1071/zo19017.
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Wildlife parasitology is a highly diverse area of research encompassing many fields including taxonomy, ecology, pathology and epidemiology, and with participants from extremely disparate scientific fields. In addition, the organisms studied are highly dissimilar, ranging from platyhelminths, nematodes and acanthocephalans to insects, arachnids, crustaceans and protists. This review of the parasites of wildlife in Australia highlights the advances made to date, focussing on the work, interests and major findings of researchers over the years and identifies current significant gaps that exist in our understanding. The review is divided into three sections covering protist, helminth and arthropod parasites. The challenge to document the diversity of parasites in Australia continues at a traditional level but the advent of molecular methods has heightened the significance of this issue. Modern methods are providing an avenue for major advances in documenting and restructuring the phylogeny of protistan parasites in particular, while facilitating the recognition of species complexes in helminth taxa previously defined by traditional morphological methods. The life cycles, ecology and general biology of most parasites of wildlife in Australia are extremely poorly understood. While the phylogenetic origins of the Australian vertebrate fauna are complex, so too are the likely origins of their parasites, which do not necessarily mirror those of their hosts. This aspect of parasite evolution is a continuing area for research in the case of helminths, but remains to be addressed for many other parasitic groups.
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Annenkova, Nataliia V., Caterina R. Giner, and Ramiro Logares. "Tracing the Origin of Planktonic Protists in an Ancient Lake." Microorganisms 8, no. 4 (April 9, 2020): 543. http://dx.doi.org/10.3390/microorganisms8040543.
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Ancient lakes are among the most interesting models for evolution studies because their biodiversity is the result of a complex combination of migration and speciation. Here, we investigate the origin of single celled planktonic eukaryotes from the oldest lake in the world—Lake Baikal (Russia). By using 18S rDNA metabarcoding, we recovered 1414 Operational Taxonomic Units (OTUs) belonging to protists populating surface waters (1–50 m) and representing pico/nano-sized cells. The recovered communities resembled other lacustrine freshwater assemblages found elsewhere, especially the taxonomically unclassified protists. However, our results suggest that a fraction of Baikal protists could belong to glacial relicts and have close relationships with marine/brackish species. Moreover, our results suggest that rapid radiation may have occurred among some protist taxa, partially mirroring what was already shown for multicellular organisms in Lake Baikal. We found 16% of the OTUs belonging to potential species flocks in Stramenopiles, Alveolata, Opisthokonta, Archaeplastida, Rhizaria, and Hacrobia. Putative flocks predominated in Chrysophytes, which are highly diverse in Lake Baikal. Also, the 18S rDNA of a number of species (7% of the total) differed >10% from other known sequences. These taxa as well as those belonging to the flocks may be endemic to Lake Baikal. Overall, our study points to novel diversity of planktonic protists in Lake Baikal, some of which may have emerged in situ after evolutionary diversification.
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Gooday, Andrew J., Genoveva F. Esteban, and Ken J. Clarke. "Organic and siliceous protistan scales in north-east Atlantic abyssal sediments." Journal of the Marine Biological Association of the United Kingdom 86, no. 4 (June 15, 2006): 679–88. http://dx.doi.org/10.1017/s0025315406013567.
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We report the occurrence of a high diversity of minute (∼1 μm diameter) organic and siliceous protistan scales in small samples (total volume ∼35 μl) of superficial sediment from the Porcupine Abyssal Plain (PAP), north-east Atlantic (4850 m water depth). Many exhibit characters by which they can be identified to species. The organic scales belong to the haptophyte genera Chrysochromulina (8–9 species), Chrysocampanula and Dolichomastix (1 species each). The siliceous scales belong to the chrysophytes Paraphysomonas vestita and Meringosphaera sp. and to the heterotrophic flagellate genus Thaumatomastix (T. dybsoeana, T. formosa, Thaumatomastix sp.). As far as we are aware, this is the first time that non-calcareous protistan scales have been observed in deep-sea sediments (although siliceous skeletal plates and cysts are reported). All scales probably originated from the upper water column and were delivered to the deep-sea floor on rapidly sinking detrital aggregates. However, naked heterotrophic flagellates are known to thrive in abyssal sediment habitats and so the possibility that some scale-bearing protists also live in benthic deep-sea environments cannot be eliminated. Many species identified at the PAP site are common in coastal marine waters around Europe; some occur as far afield as Tasmania and New Zealand. Five Chrysochromulina species are known from central oceanic areas, including parts of the North Atlantic, while another species, C. pringsheimii, is reported from a British freshwater lake. We retrieved ∼15% of the 55 named Chrysochromulina species (∼8% of the estimated total number of species in this diverse group) in the ∼35 μl of abyssal sediment. Because the scales can persist and be identified after cell death, they may provide useful time- and space-averaged information about the distribution of protist species in marine habitats. The long-term fate of the scales on the sea-floor is unknown. It is possible that at least some of the organic scales are preserved as microfossils in deep-sea sediments.
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Bjorbækmo, Marit F. Markussen, Andreas Evenstad, Line Lieblein Røsæg, Anders K. Krabberød, and Ramiro Logares. "The planktonic protist interactome: where do we stand after a century of research?" ISME Journal 14, no. 2 (November 4, 2019): 544–59. http://dx.doi.org/10.1038/s41396-019-0542-5.
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Abstract Microbial interactions are crucial for Earth ecosystem function, but our knowledge about them is limited and has so far mainly existed as scattered records. Here, we have surveyed the literature involving planktonic protist interactions and gathered the information in a manually curated Protist Interaction DAtabase (PIDA). In total, we have registered ~2500 ecological interactions from ~500 publications, spanning the last 150 years. All major protistan lineages were involved in interactions as hosts, symbionts (mutualists and commensalists), parasites, predators, and/or prey. Predation was the most common interaction (39% of all records), followed by symbiosis (29%), parasitism (18%), and ‘unresolved interactions’ (14%, where it is uncertain whether the interaction is beneficial or antagonistic). Using bipartite networks, we found that protist predators seem to be ‘multivorous’ while parasite–host and symbiont–host interactions appear to have moderate degrees of specialization. The SAR supergroup (i.e., Stramenopiles, Alveolata, and Rhizaria) heavily dominated PIDA, and comparisons against a global-ocean molecular survey (TARA Oceans) indicated that several SAR lineages, which are abundant and diverse in the marine realm, were underrepresented among the recorded interactions. Despite historical biases, our work not only unveils large-scale eco-evolutionary trends in the protist interactome, but it also constitutes an expandable resource to investigate protist interactions and to test hypotheses deriving from omics tools.
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Thompson, Andrew R., Andrea J. Roth-Monzón, Zachary T. Aanderud, and Byron J. Adams. "Phagotrophic Protists and Their Associates: Evidence for Preferential Grazing in an Abiotically Driven Soil Ecosystem." Microorganisms 9, no. 8 (July 21, 2021): 1555. http://dx.doi.org/10.3390/microorganisms9081555.
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The complex relationship between ecosystem function and soil food web structure is governed by species interactions, many of which remain unmapped. Phagotrophic protists structure soil food webs by grazing the microbiome, yet their involvement in intraguild competition, susceptibility to predator diversity, and grazing preferences are only vaguely known. These species-dependent interactions are contextualized by adjacent biotic and abiotic processes, and thus obfuscated by typically high soil biodiversity. Such questions may be investigated in the McMurdo Dry Valleys (MDV) of Antarctica because the physical environment strongly filters biodiversity and simplifies the influence of abiotic factors. To detect the potential interactions in the MDV, we analyzed the co-occurrence among shotgun metagenome sequences for associations suggestive of intraguild competition, predation, and preferential grazing. In order to control for confounding abiotic drivers, we tested co-occurrence patterns against various climatic and edaphic factors. Non-random co-occurrence between phagotrophic protists and other soil fauna was biotically driven, but we found no support for competition or predation. However, protists predominately associated with Proteobacteria and avoided Actinobacteria, suggesting grazing preferences were modulated by bacterial cell-wall structure and growth rate. Our study provides a critical starting-point for mapping protist interactions in native soils and highlights key trends for future targeted molecular and culture-based approaches.
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Noda, Satoko, Toshiya Iida, Osamu Kitade, Hideaki Nakajima, Toshiaki Kudo, and Moriya Ohkuma. "Endosymbiotic Bacteroidales Bacteria of the Flagellated Protist Pseudotrichonympha grassii in the Gut of the Termite Coptotermes formosanus." Applied and Environmental Microbiology 71, no. 12 (December 2005): 8811–17. http://dx.doi.org/10.1128/aem.71.12.8811-8817.2005.
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ABSTRACT A unique lineage of bacteria belonging to the order Bacteroidales was identified as an intracellular endosymbiont of the protist Pseudotrichonympha grassii (Parabasalia, Hypermastigea) in the gut of the termite Coptotermes formosanus. We identified the 16S rRNA, gyrB, elongation factor Tu, and groEL gene sequences in the endosymbiont and detected a very low level of sequence divergence (<0.9% of the nucleotides) in the endosymbiont population within and among protist cells. The Bacteroidales endosymbiont sequence was affiliated with a cluster comprising only sequences from termite gut bacteria and was not closely related to sequences identified for members of the Bacteroidales attached to the cell surfaces of other gut protists. Transmission electron microscopy showed that there were numerous rod-shaped bacteria in the cytoplasm of the host protist, and we detected the endosymbiont by fluorescence in situ hybridization (FISH) with an oligonucleotide probe specific for the 16S rRNA gene identified. Quantification of the abundance of the Bacteroidales endosymbiont by sequence-specific cleavage of rRNA with RNase H and FISH cell counting revealed, surprisingly, that the endosymbiont accounted for 82% of the total bacterial rRNA and 71% of the total bacterial cells in the gut community. The genetically nearly homogeneous endosymbionts of Pseudotrichonympha were very abundant in the gut symbiotic community of the termite.
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Šlapeta, Jan, David Moreira, and Purificación López-García. "The extent of protist diversity: insights from molecular ecology of freshwater eukaryotes." Proceedings of the Royal Society B: Biological Sciences 272, no. 1576 (August 17, 2005): 2073–81. http://dx.doi.org/10.1098/rspb.2005.3195.
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Classical studies on protist diversity of freshwater environments worldwide have led to the idea that most species of microbial eukaryotes are known. One exemplary case would be constituted by the ciliates, which have been claimed to encompass a few thousands of ubiquitous species, most of them already described. Recently, molecular methods have revealed an unsuspected protist diversity, especially in oceanic as well as some extreme environments, suggesting the occurrence of a hidden diversity of eukaryotic lineages. In order to test if this holds also for freshwater environments, we have carried out a molecular survey of small subunit ribosomal RNA genes in water and sediment samples of two ponds, one oxic and another suboxic, from the same geographic area. Our results show that protist diversity is very high. The majority of phylotypes affiliated within a few well established eukaryotic kingdoms or phyla, including alveolates, cryptophytes, heterokonts, Cercozoa, Centroheliozoa and haptophytes, although a few sequences did not display a clear taxonomic affiliation. The diversity of sequences within groups was very large, particularly that of ciliates, and a number of them were very divergent from known species, which could define new intra-phylum groups. This suggests that, contrary to current ideas, the diversity of freshwater protists is far from being completely described.
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Anderson, O. Roger. "Living Together in the Plankton: A Survey of Marine Protist Symbioses." Acta Protozoologica 53, no. 1 (2014): 29–38. http://dx.doi.org/10.4467/16890027ap.13.0019.1116.
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Our best evidence is that life arose in the marine environment, and over many millennia of evolutionary proliferation, punctuated by occasional massive extinctions, marine protists have developed remarkably elegant and sometimes complex relationships with prokaryotic and eukaryotic symbionts. Current evidence of the range of marine protist taxa possessing symbionts, including their diversity and physiological functional relationships, is reviewed within an ecological context. Some perspectives are presented on potential opportunities for new avenues of research in unraveling the remarkable adaptive value of two or more genetically diverse marine unicellular organisms living in a close structural and physiological relationship.