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Biological soil crusts (BSC) are associations of different macro and microorganisms and aggregated soil particles located on the surface of soils in many different habitats. BSC harbour a diverse and complex community of ciliates and testate amoebae. These phagotrophic protists play an important role in C and N recycling in soil ecosystems but have not been frequently studied in BSC. In this context, the effects of three increasing N inputs on ciliates and testate amoebae in crusts from a semi-arid Mediterranean ecosystem were evaluated. A field experiment with artificial N-deposition was designed to mimic the effects caused by anthropogenic N depositions. The results have shown that the protist populations of these semi-arid Mediterranean environments have lower species richness than other soil environments. The increase in N produces a net loss of diversity in the populations studied and shifts in the community structure. It has also been shown that some ciliates and testate amoebae, due to their population responses to increased N concentrations, could potentially be used as bio-indicators of N contamination in these BSCs. [ABSTRACT FROM AUTHOR]

Although learning is often viewed as a unique feature of organisms with complex nervous systems, single-celled organisms also demonstrate basic forms of learning. The giant ciliate Stentor coeruleus responds to mechanical stimuli by contracting into a compact shape, presumably as a defense mechanism. When a Stentor cell is repeatedly stimulated at a constant level of force, it will learn to ignore that stimulus but will still respond to stronger stimuli. Prior studies of habituation in Stentor reported a graded response, suggesting that cells transition through a continuous range of response probabilities. By analyzing single cells using an automated apparatus to deliver calibrated stimuli, we find that habituation occurs via a single step-like switch in contraction probability within each cell, with the graded response in a population arising from the random distribution of switching times in individual cells. This step-like response allows Stentor behavior to be represented by a simple two-state model whose parameters can be estimated from experimental measurements. We find that transition rates depend on stimulus force and also on the time between stimuli. The ability to measure the behavior of the same cell to the same stimulus allowed us to quantify the functional heterogeneity among single cells. Together, our results suggest that the behavior of Stentor is governed by a two-state stochastic machine whose transition rates are sensitive to the time series properties of the input stimuli. [Display omitted] • Stentor is a single-celled organism that can learn to ignore repetitive stimuli • Individual cells learn by switching from a responsive to a non-responsive state • Stepwise transitions of individual cells produce a graded response in a population • Transition rates depend on stimulus force as well as the time between stimuli Rajan, Makushok, et al. analyze learning in the unicellular organism Stentor coeruleus , which habituates to mechanical stimuli. A gradually decreasing response in a population of cells is due to step-like transitions in individual cells. Transition rates between the responsive and non-responsive states depend on stimulus intensity and frequency. [ABSTRACT FROM AUTHOR]

Ciliates in the class Prostomatea play an important role in the global microbial loop due to their significant abundances and broad feeding strategies at the foundation of food webs. Despite their importance in ecosystems, the taxonomy and systematics of this group of ciliates has long been poorly understood, with this being especially true for members of the family Lagynusidae. Here we examine four lagynusids collected from sandy beaches in China, using silver-staining and 18S rRNA gene sequencing techniques. These investigations revealed two new genera and two new species and provided details for two little known forms: Penardella marina gen. nov., sp. nov., Apolagynus cucumis (as reported by Penard. Études sur les infusoires d'eau douce. Georg and Cie, Genève, 1922) gen. nov., comb. nov., Lagynus minutus sp. nov., and Lagynus elegans (Engelmann in Z Wiss Zool 11:347-393, 1862) Quennerstedt (Acta Univ Lund 4:1-48, 1867). Penardella gen. nov. can be morphologically distinguished by having more than three dikinetidal perioral kineties. Apolagynus gen. nov. differs from the closely related genus Lagynus in the absence of a conspicuous neck-like region. The ciliature of Apolagynus cucumis is revealed here for the first time, which demonstrates the classification of this species within Lagynusidae. Furthermore, Apolagynus binucleatus (Jiang et al., 2021) comb. nov. is established according to the new finding. The results of our phylogenetic analyses based on the 18S rRNA gene support the establishment of two new genera and indicate that Lagynusidae is monophyletic, which further strengthens its valid taxonomic status., Competing Interests: Conflict of interestAuthors declare that they have no conflict of interest., (© The Author(s) 2023.)

One of the most diverse clades of ciliated protozoa, the class Spirotrichea, displays a series of unique characters in terms of eukaryotic macronuclear (MAC) genome, including high fragmentation that produces nanochromosomes. However, the genomic diversity and evolution of nanochromosomes and gene families for spirotrich MAC genomes are poorly understood. In this study, we assemble the MAC genome of a representative euplotid (a new model organism in Spirotrichea) species, Euplotes aediculatus . Our results indicate that: (a) the MAC genome includes 35,465 contigs with a total length of 97.3 Mb and a contig N50 of 3.4 kb, and contains 13,145 complete nanochromosomes and 43,194 predicted genes, with the majority of these nanochromosomes containing tiny introns and harboring only one gene; (b) genomic comparisons between E. aediculatus and other reported spirotrichs indicate that average GC content and genome fragmentation levels exhibit interspecific variation, and chromosome breaking sites (CBSs) might be lost during evolution, resulting in the increase of multi-gene nanochromosome; (c) gene families associated with chitin metabolism and FoxO signaling pathway are expanded in E. aediculatus , suggesting their potential roles in environment adaptation and survival strategies of E. aediculatus ; and (d) a programmed ribosomal frameshift (PRF) with a conservative motif 5'-AAATAR-3' tends to occur in longer genes with more exons, and PRF genes play an important role in many cellular regulation processes., Supplementary Information: The online version contains supplementary material available at 10.1007/s42995-023-00175-0., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest., (© The Author(s) 2023.)

Protozoal infections are a world-wide problem. The toxicity and somewhat low effectiveness of the existing drugs require the search for new ways of protozoa suppression. Snake venom contains structurally diverse components manifesting antiprotozoal activity; for example, those in cobra venom are cytotoxins. In this work, we aimed to characterize a novel antiprotozoal component(s) in the Bungarus multicinctus krait venom using the ciliate Tetrahymena pyriformis as a model organism. To determine the toxicity of the substances under study, surviving ciliates were registered automatically by an original BioLaT-3.2 instrument. The krait venom was separated by three-step liquid chromatography and the toxicity of the obtained fractions against T. pyriformis was analyzed. As a result, 21 kDa protein toxic to Tetrahymena was isolated and its amino acid sequence was determined by MALDI TOF MS and high-resolution mass spectrometry. It was found that antiprotozoal activity was manifested by β-bungarotoxin (β-Bgt) differing from the known toxins by two amino acid residues. Inactivation of β-Bgt phospholipolytic activity with p -bromophenacyl bromide did not change its antiprotozoal activity. Thus, this is the first demonstration of the antiprotozoal activity of β-Bgt, which is shown to be independent of its phospholipolytic activity.

This review provides background and perspective for the articles contributing to the Special Issue of MDPI Micro-organisms on Paramecium as a Modern Model Organism. The six articles cover a variety of topics, each taking advantage of an important aspect of Paramecium biology: peripheral surface proteins that are developmentally regulated, endosymbiont algae and bacteria, ion channel regulation by calmodulin, regulation of cell mating reactivity and senescence, and the introns that dwell in the large genome. Each article highlights a significant aspect of Paramecium and its versatility.

Our knowledge of ciliate endosymbiont diversity greatly expanded over the past decades due to the development of characterization methods for uncultivable bacteria. Chlamydia-like bacteria have been described as symbionts of free-living amoebae and other phylogenetically diverse eukaryotic hosts. In the present work, a systematic survey of the bacterial diversity associated with the ciliate Euplotes octocarinatus strain Zam5b-1 was performed, using metagenomic screening as well as classical full-cycle rRNA approach, and a novel chlamydial symbiont was characterized. The metagenomic screening revealed 16S rRNA gene sequences from Polynucleobacter necessarius, three previously reported accessory symbionts, and a novel chlamydia-like bacterium. Following the full-cycle rRNA approach, we obtained the full-length 16S rRNA gene sequence of this chlamydia-like bacterium and developed probes for diagnostic fluorescence in situ hybridizations. The phylogenetic analysis of the 16S rRNA gene sequences unambiguously places the new bacterium in the family Rhabdochlamydiaceae. This is the first report of chlamydia-like bacterium being found in Euplotes. Based on the obtained data, the bacterium is proposed as a new candidate genus and species: "Candidatus Euplotechlamydia quinta.", (© 2022 International Society of Protistologists.)

Terrestrial plant roots exude compounds that promote the proliferation of microorganisms, a phenomenon called the rhizosphere effect. However, little is known about the influence of roots of aquatic plants on microbial populations. We compared cultivable bacteria and protozoa from the rhizoplanes ofAzolla filiculoidesLam.,Lemna gibbaL., andRicciocarpus natansL., collected at the Tecocomulco Lagoon (Hidalgo, Mexico). The functional bacterial groups isolated fromA. filiculoides,L. gibbaandR. natans, were macro- and microscopically characterized, and phylogenetically identified using the 16S rDNA gen. About 96% of isolates corresponded to Gram-negative bacteria, and potential N-fixing free-living bacteria (diazotrophic bacteria) were the most abundant. Molecular analysis detected 15 bacterial genera in the rhizoplane ofR. natans, whereasA. filiculoidesandL. gibbaonly yielded five genera, among whichAeromonaswas predominant. Twenty-five genera of flagellated and 20 genera of ciliated protozoa were identified.Bodowas the more abundant flagellated, whereasHalteriawas the most frequent ciliate. All three aquatic plants showed the rhizospheric effects. The most abundant and diverse community of protozoa was found inA. filiculoides, which also had the most abundant bacterial community, but the highest bacterial diversity was found inR. natans. [ABSTRACT FROM PUBLISHER]

Cryptocaryonosis is a major problem for mariculture, and the absence of suitable sero-surveillance tools for the detection of cryptocaryonosis makes it difficult to screen Cryptocaryon irritans-infected fish, particularly asymptomatic fish. In this study, we proposed a serum-based assay using selected C. irritans proteins to screen infected and asymptomatic fish. Eight highly expressed genes were chosen from an earlier study on C. irritans expressed sequence tags and ciliate glutamine codons were converted to universal glutamine codons. The chemically synthesized C. irritans genes were then expressed in an Escherichia coli expression host under optimized conditions. Five C. irritans proteins were successfully expressed in E. coli and purified by affinity chromatography. These proteins were used as antigens in an enzyme-linked immunosorbent assay ( ELISA) to screen sera from experimentally immunized fish and naturally infected fish. Sera from both categories of fish reacted equally well with the expressed C. irritans recombinant proteins as well as with sonicated theronts. This study demonstrated the utility of producing ciliate recombinant proteins in a heterologous expression host. An ELISA was successfully developed to diagnose infected and asymptomatic fish using the recombinant proteins as antigens. [ABSTRACT FROM AUTHOR]

Phylogenetic analyses of ciliated protozoa have been increasingly relied on multigene information, which was revealed to provide more robust interpretations than single-gene information. Previous studies showed that Amphisiellidae was an extremely divergent group within the order Stichotrichida, with species widely dispersed throughout the stichotrichid assemblage, while Trachelostylidae, excluding gonostomatid species, is a monophyletic group within the order Sporadotrichida. In the present study, we provide 38 new sequences of SSU-rDNA, ITS1-5.8S-ITS2 and LSU-rDNA genes to infer phylogenetic relationships among all taxa available in Amphisiellidae and Trachelostylidae. The results indicate that: (1) Amphisiellidae is polyphyletic, with Amphisiella , Hemiamphisiella , Orthoamphisiella , Uroleptoides , and Urospinula distributing in different clades; (2) Amphisiella is separated into two clades in phylogenetic trees, corroborated by difference in cortical granule distribution. Thus, cortical granule pattern and distribution may be strong diagnostic features to divide Amphisiella species into two subgenera; (3) the monophyly of Trachelostylidae sensu Berger (2008) is strongly supported, suggesting it is a well-defined family; (4) Gonostomatidae is confirmed to be a valid family. [ABSTRACT FROM AUTHOR]

The global ever-growing concerns about multi-drug resistant (MDR) microbes leads to urgent demands for exploration of new antibiotics including antimicrobial peptides (AMPs). Here we demonstrated that a cDNA from Ciliata Paramecium caudatum , designated Pcamp1 , coded for a protein with features characteristic of AMPs, which is not homologous to any AMPs currently known. Both the C-terminal 91 amino acid residues of PcAMP1, cPcAMP1, expressed in Escherichia coli and the C-terminal 26 amino acid residues (predicted mature AMP), cPcAMP1/26, synthesized, underwent a coil-to-helix transition in the presence of TFE, SDS or DPC. Functional assays revealed that cPcAMP1 and cPcAMP1/26 were both able to kill Aeromonas hydrophila and Staphylococcus aureus . ELISA showed that cPcAMP1 and cPcAMP1/26 were able to bind to microbe-associated molecular pattern molecules LPS and LTA, which was further corroborated by the observations that cPcAMP1 could deposit onto the bacterial membranes. Importantly, both cPcAMP1 and cPcAMP1/26 were able to induce bacterial membrane permeabilization and depolarization, and to increase intracellular ROS levels. Additionally, cPcAMP1 and cPcAMP1/26 were not cytotoxic to mammalian cells. Taken together, our results show that PcAMP1 is a potential AMP with a membrane selectivity towards bacterial cells, which renders it a promising template for the design of novel peptide antibiotics against MDR microbes. It also shows that use of signal conserved sequence of AMPs can be an effective tool to identify potential AMPs across different animal classes. [ABSTRACT FROM AUTHOR]

Two colepid ciliates, Levicoleps taehwae nov. spec. and L. biwae jejuensis nov. subspec., were collected from the brackish water of the Taehwa River and a small freshwater pond in Jeju Island, South Korea, respectively. Their living morphology, infraciliature, and small subunit (SSU) rRNA gene sequences were determined using standard methods. Barrel-shaped L taehwae nov. spec. is a small ciliate with an average size of 45 9 25 lm in vivo, about 15 ciliary rows each composed of 12 monokinetids and two perioral dikinetids, and two 20 µm-long caudal cilia. The sequence length and GC content of the SSU rRNA gene are 1,669 bp, 44.5%. This novel species is similar in body size to Coleps hirtus, and has six armor tiers and hirtus-type tier plates, and the same number of ciliary rows as C. hirtus; however, it can be distinguished from the latter by the absence of armor spines and its sequence similarity of SSU rRNA gene is about 92.8% which indicates that it is a distinct form. Levicoleps biwae jejuensis nov. subspec., is a medium colepid ciliate which has a barrel-shaped body, about 22 somatic kineties and 16 transverse ciliary rows, three mini adoral organelles, and four 15 µm-long caudal cilia. The sequence length and GC content of the SSU rRNA gene are 1,666 bp and 44.4%. [ABSTRACT FROM AUTHOR]

Species composition and distribution of rumen ciliates were investigated in the rumen contents of six Anatolian water buffaloes living in Kastamonu, Turkey. Thirty-seven species and 19 morphotypes belonging to 11 genera were identified, all being first reports of rumen ciliates from Anatolian water buffaloes. The mean number of ciliates was 70.5 ± 62.3 × 104 cells in 1 mL of rumen contents, while the average number of ciliate species per host was 17.5 ± 3.6. Dasytricha ruminantium, Entodinium simulans, and En. longinucleatum were found to be the dominant species occurring in all animals. Entodinium ellipsoideum, Eudiplodinium dilobum, and Ostracodinium munham were isolated from buffaloes for the first time. No previously unknown species were observed. [ABSTRACT FROM AUTHOR]

The growth rates of ciliates estimated under natural conditions with the widely used size fractionation method are much lower than those observed in cultures. However, recent studies performed with a modified dilution method demonstrated that the size fractionation method underestimates the ciliate growth, because it does not remove predators of the same size as the organisms studied. Thus, it is still unresolved whether ciliates are food-limited in different systems and whether their growth rates are indeed lower than those in cultures. This study was conducted in highly eutrophic Lake Gardno using a modified dilution method. Each time, two dilution experiments were performed (around noon and around midnight). Four small, common ciliates from the genera Rimostrombidium, Tintinnidium, Cyclidium, and Urotricha were studied. The first three ciliates demonstrated very high mean diel growth rates exceeding 0.1 h-1, which corresponded well to the highest values reported in the literature for the ciliate growth in cultures at similar temperatures. Tintinnidium sp. demonstrated a diel growth rhythm. Urotricha sp. was sensitive to the experimental procedure, and measurements of its growth were unsuccessful. Concentrations of food particles were analyzed to check whether organisms studied were food satiated. [ABSTRACT FROM AUTHOR]

Genome architecture varies greatly among eukaryotes. This diversity may profoundly affect the origin and maintenance of genetic variation within a population. Ciliates are microbial eukaryotes with unusual genome features, such as the separation of germline and somatic genomes within a single cell and amitotic division. These features have previously been proposed to increase the rate of molecular evolution in these species. Here, we assessed the fitness effects of genetic variation in the two genomes of natural isolates of the ciliate Tetrahymena thermophila. We find more extensive genetic variation in fitness in the transcriptionally silent germline genome than in the expressed somatic genome. Surprisingly, this variation is not primarily deleterious, but has both beneficial and deleterious effects. We conclude that Tetrahymena genome architecture allows for the maintenance of genetic variation that would otherwise be eliminated by selection. We consider the effect of selection on the two genomes and the impacts of reproductive strategies and the mechanism of sex determination on the structure of this variation. [ABSTRACT FROM AUTHOR]

Toxic effects of diuron and carbofuran on Paramecium caudatum were evaluated. Acute and chronic tests were conducted with diuron and carbofuran active ingredients and their commercial formulations, Diuron Nortox ® 500 SC and Furadan ® 350 SC, respectively. The sensitivity range of P. caudatum to reference substance sodium chloride was established. A preliminary risk assessment of diuron and carbofuran for Brazilian water bodies was performed. The tests indicated that toxicity of pure diuron and its commercial formulation was similar, while the commercial product carbofuran was more toxic than its pure form. In acute tests, readings were carried out at 2, 3, 4 and 6 h and showed an increase of mortality with increasing exposure time. The sensitivity of P. caudatum to NaCl ranged from 3.31 to 4.44 g L −1 , averaging 3.88 g L −1 . For diuron, the 6 h LC 50 was 64.6 ± 3.3 mg L −1 for its pure form and 62.4 ± 2.5 mg L −1 for its commercial formulation. Carbofuran active ingredient was less toxic than that of diuron, presenting a 6 h LC 50 of 142.0 ± 2.4 mg L −1 for its pure form and 70.4 ± 2.2 mg L −1 for its commercial product. Chronic tests showed that these pesticides cause significant decrease on population growth, generation number and biomass of P. caudatum . The 24 h IC 50 was 7.10 ± 0.58 mg L −1 for pure diuron, 6.78 ± 0.92 mg L −1 for commercial diuron, 22.95 ± 3.57 mg L −1 for pure carbofuran and 4.98 ± 0.62 mg L −1 for commercial carbofuran. Preliminary risk assessment indicated that diuron and carbofuran present potential ecological risks for Brazilian water bodies. P. caudatum was a suitable and sensitive test organism to evaluate diuron and carbofuran toxicity to freshwater protozooplankton and, taking into account the relevant role of protozoans in aquatic environments, we strongly recommend its inclusion in ecotoxicological studies. [ABSTRACT FROM AUTHOR]

We present continuous bi-weekly to bi-monthly dinoflagellate cyst, tintinnid loricae and tintinnid cyst fluxes at two mooring sites in Hudson Bay (subarctic Canada) from October 2005 to September 2006. The total dinoflagellate cyst fluxes at the site on the western side of the bay ranged from 4600 to 53,600 cysts m − 2 day − 1 (average 20,000 cysts m − 2 day − 1 ), while on average three times higher fluxes (average 62,300 cysts m − 2 day − 1 ) were recorded at the site on the eastern side of the bay with a range from 2700 to 394,800 cysts m − 2 day − 1 . These values are equivalent to the average fluxes calculated from the top 1-cm sediment layer of 210Pb-dated box cores at corresponding locations, and hence lend support to the use of sediment dinoflagellate cysts in palaeoceanography. Tintinnid fluxes ranged from 1200 to 80,000 specimens m − 2 day − 1 (average 32,100 tintinnids m − 2 day − 1 ) in the west, and 1600 to 1,240,800 specimens m − 2 day − 1 (average 106,800 tintinnids m − 2 day − 1 ) in the east, with the highest Salpingella sp. fluxes recorded during the sea-ice cover season. The dinoflagellate cyst species diversity recorded in the traps was similar at the two environmentally differing locations, with cold-water (e.g., Echinidinium karaense , Islandinium minutum , Islandinium ? cezare , Polykrikos sp. var. arctica, Spiniferites elongatus ), cosmopolitan (e.g., Operculodinium centrocarpum , Spiniferites ramosus , Brigantedinium ) and typical warmer-water (e.g., Echinidinium aculeatum , Islanidium brevispinosum ) species present. Furthermore, the species-specific timing of cyst production behaved similarly relative to the seasonal sea-ice cycle at both locations. Cyst species proportions and species-specific flux quantities, however, differed between the two sites and corresponded to the quantities and species assemblages recorded in the surface sediment, with the exception of cysts of Polarella glacialis and cf. Biecheleria sp. that seem not to preserve well in sediment but were abundant in both traps. Otherwise, cyst assemblage at the western trap site was dominated by O . centrocarpum and S . elongatus while at the eastern site very high quantities of cysts of Pentapharsodinium dalei were recorded. Our data do not lend support to the hypothesis that trophic status solely determines whether cyst production takes place under-ice or in the open water, since cysts of light-dependent (phototrophic) and light-independent (heterotrophic) dinoflagellates are recorded during both conditions. Most importantly, negligible under-ice cyst production is recorded during the deep arctic winter. [ABSTRACT FROM AUTHOR]

Many freshwater protists harbor unicellular green algae within their cells, but little is known of their degree of integration and specificity. Using algae-targeted PCR of whole ciliate cells collected at irregular intervals over 15 months from Lake Biwa, Japan, we explored the SSU-ITS rDNA of the endosymbiotic algae and its changes over time, obtaining sequences of algal rDNA fragments from four ciliate species. A high proportion of clonal algae was evident within the ciliate cells. The differences observed in those sequences from the SSU through to the ITS region were less than 1%. The name ‘Chlorb’ is proposed for these algae, with the implication that they represent a single ‘species.’ The sequences of the algal DNA fragments were identical for any given host species throughout the collection period, thus we conclude that these four ciliates stably retain their algae over long term. In contrast, algal DNA fragments obtained from Didinium sp. were variable within each sample, which indicates that this ciliate only temporarily holds its algal cells. The ITS1 sequences of Chlorb populations are close (at intraspecific level) to those of algae isolated from ciliates in Austria, which raises the possibility that Chlorb algae are universally shared as symbionts among various ciliates. [ABSTRACT FROM AUTHOR]

Species composition and concentration of rumen ciliate protozoa were investigated in the rumen contents of 14 domestic sheep and 1 goat living in Bishkek, Kyrgyzstan. This is the first report on rumen ciliates from ruminants living in Kyrgyzstan. In sheep 12 genera, 28 species and 12 morphotypes were detected, whereas in goat 8 genera, 12 species and 4 morphotypes were detected. The density of ciliates in sheep was (28.1 ± 20.0) x 104 cells mL-1 and in goat was 37.0 x 104 cells mL-1. Dasytricha ruminantium, Isotricha prostoma, Entodinium simulans and Ophryoscolex caudatus were major species (100%) in sheep, and for the first time, Diplodinium rangiferi was detected in a domestic goat. [ABSTRACT FROM AUTHOR]

Interphase specimens, aspects of physiological reorganization and divisional morphogenesis were investigated in a strain of a hypotrichous ciliate highly similar to Urostyla grandis Ehrenberg, (type species of Urostyla), collected from a mangrove area in the estuary of the Paraíba do Sul river (Rio de Janeiro, Brazil). The results revealed that albeit interphase specimens match with the known morphologic variability in U. grandis, morphogenetic processes have conspicuous differences. Parental adoral zone is entirely renewed during morphogenesis, and marginal cirri exhibit a unique combination of developmental modes, in which left marginal rows originate from multiple anlagen arising from innermost left marginal cirral row, whereas right marginal ciliature originates from individual within-row anlagen. Based on such characteristics, a new subspecies, namely U. grandis wiackowskii subsp. nov. is proposed, and consequently, U. grandis grandis Ehrenberg, stat. nov. is established. Bayesian and maximum-likelihood analyses of the 18S rDNA unambiguously placed U. grandis wiackowskii as adelphotaxon of a cluster formed by other U. grandis sequences. The implications of such findings to the systematics of Urostyla are discussed. [ABSTRACT FROM AUTHOR]

Alveolate (ciliates and dinoflagellates) grazers are integral components of the marine food web and must therefore be able to sense a range of mechanical and chemical signals produced by prey and predators, integrating them via signal transduction mechanisms to respond with effective prey capture and predator evasion behaviors. However, the sensory biology of alveolate grazers is poorly understood. Using novel techniques that combine electrophysiological measurements and high-speed videomicroscopy, we investigated the sensory biology of Favella sp., a model alveolate grazer, in the context of its trophic ecology. Favella sp. produced frequent rhythmic depolarizations (~500 ms long) that caused backward swimming and are responsible for endogenous swimming patterns relevant to foraging. Contact of both prey cells and non-prey polystyrene microspheres at the cilia produced immediate mechanostimulated depolarizations (~500 ms long) that caused backward swimming, and likely underlie aggregative swimming patterns of Favella sp. in response to patches of prey. Contact of particles at the peristomal cavity that were not suitable for ingestion resulted in depolarizations after a lag of ~600 ms, allowing time for particles to be processed before rejection. Ingestion of preferred prey particles was accompanied by transient hyperpolarizations (~1 s) that likely regulate this step of the feeding process. Predation attempts by the copepod Acartia tonsa elicited fast (~20 ms) animal-like action potentials accompanied by rapid contraction of the cell to avoid predation. We have shown that the sensory mechanisms of Favella sp. are finely tuned to the type, location, and intensity of stimuli from prey and predators. [ABSTRACT FROM AUTHOR]

Tetrahymena thermophila is a ciliate with hundreds of cilia primarily used for cellular motility. These cells propel themselves by generating hydrodynamic forces through coordinated ciliary beating. The coordination of cilia is ensured by the polarized organization of basal bodies (BBs), which exhibit remarkable structural and molecular conservation with BBs in other eukaryotes. During each cell cycle, massive BB assembly occurs and guarantees that future Tetrahymena cells gain a full complement of BBs and their associated cilia. BB duplication occurs next to existing BBs, and the predictable patterning of new BBs is facilitated by asymmetric BB accessory structures that are integrated with a membrane-associated cytoskeletal network. The large number of BBs combined with robust molecular genetics merits Tetrahymena as a unique model system to elucidate the fundamental events of BB assembly and organization. [ABSTRACT FROM AUTHOR]

As the foundations of food webs, protozoa are essential to the success of an ecological system. These organisms are often overlooked, and research in the Americas is sparse. Recent samplings conducted in freshwater canals and ponds in Florida, USA, have revealed Loxodes rex, an alleged endemic ciliate species. Originally described as endemic to tropical Africa, L. rex has been considered a prime candidate for proof of microbial endemism. Our studies have shown this giant, non-encysting ciliate to be thriving in subtropical Florida. Our observations are novel and include both the first record of occurrence for the Americas and the first high-quality in vivo images for this charismatic species. [ABSTRACT FROM AUTHOR]

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The thermal water ecosystem of Diyadin (Agri region) is poorly known in terms of biodiversity, as only few bacteria species were identified and some of their specific enzymes were isolated. However, the geological structure of this old inactive volcanic zone as well as the chemical composition of the thermal water characterized by therapeutic properties and temperatures up to 64°C were thoroughly studied. Diyadin zone has been insufficiently capitalized from the tourist and industrial viewpoints so far, but the discovery of some gold deposits seems to revitalize its economy. The present paper is the first one dedicated to the ciliates living in surface thermal waters; 9 species have been identified till present. The data are preliminary and they will be completed with other data after the inventory of other protozoa and metazoa species, which could represent new taxa or varieties of the species originating in the Murat River and adapted to the special abiotical factors of this ecosystem. [ABSTRACT FROM AUTHOR]

Benthic marine protists have been well documented from shallow marine benthic habitats but remain understudied in deeper habitats on continental shelves and slopes, particularly in the Northeastern Gulf of Mexico (NEGOM). This region was affected by a deep water oil well failure (BP-Deepwater Horizon, 2010). The combination of a lack of information on deep sea microbenthic communities and the potential for benthic microbial petroleum mineralization prompted this investigation. Water column and nepheloid layer samples were obtained via Niskin bottles and a multicorer respectively at stations across the NEGOM to: (1) determine whether nepheloid and water column communities are distinct and (2) assess benthic species richness relative to sediment PAH contamination. Phylum specific 18S rRNA gene amplification was used to construct clone libraries of ciliate assemblages. BLAST searches in the NCBI database indicated that a majority (~75%) of the clone sequences corresponded (94–100% similarity) with listed, yet unclassified sequences. Several putative species were common at most site locations and depths. Many known benthic ciliates, such as Uronychia transfuga , Uronychia setigera , and Spirotrachelostyla tani , were common in the nepheloid layer samples and not recovered in water column samples. Ciliated protist species richness increased with PAH levels found in surface sediments, suggesting a positive microbial response to petroleum enrichment of the benthos. The presence of previously unknown microbenthic communites in the nephaloid layer over oceanic clay–silt muds alters our view of microbial processes in the deep sea and merits investigation of the microbial processes and rates of microbial mineralization and biomass production important to global biogeochemistry. [ABSTRACT FROM AUTHOR]