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In this paper, we explore the hydrodynamics of spheroidal active particles in viscosity gradients. This work provides a more accurate modelling approach, in comparison to spherical particles, for anisotropic organisms such as Paramecium swimming through inhomogeneous environments, but more fundamentally examines the influence of particle shape on viscotaxis. We find that spheroidal squirmers generally exhibit dynamics consistent with their spherical analogues, irrespective of the classification of swimmers as pushers, pullers or neutral swimmers. However, the slenderness of the spheroids tends to reduce the impact of viscosity gradients on their dynamics; when a swimmer becomes more slender, the viscosity difference across its body is reduced, which leads to slower reorientation. We also derive the mobility tensor for passive spheroids in viscosity gradients, generalizing previous results for spheres and slender bodies. This work enhances our understanding of how shape factors into the dynamics of passive and active particles in viscosity gradients, and offers new perspectives that could aid the control of both natural and synthetic swimmers in complex fluid environments. [ABSTRACT FROM AUTHOR]

Extant symbioses illustrate endosymbiosis is a driving force for evolution and diversification. In the ciliate Paramecium bursaria, the endosymbiotic alga Chlorella variabilis in perialgal vacuole localizes beneath the host cell cortex by adhesion between the perialgal vacuole membrane and host mitochondria. We investigated whether host mitochondria are also affected by algal endosymbiosis. Transmission electron microscopy of host cells showed fewer mitochondria beneath the algae-bearing host cell cortex than that of alga-free cells. To compare the density and distribution of host mitochondria with or without symbiotic algae, we developed a monoclonal antibody against Paramecium mitochondria. Immunofluorescence microscopy with the monoclonal antibody showed that the mitochondrial density of the algae-bearing P. bursaria was significantly lower than that of the alga-free cells. The total cell protein concentration of alga-free P. bursaria cells was approximately 1.8-fold higher than that of algae-bearing cells, and the protein content of mitochondria was significantly higher in alga-free cells than that in the algae-bearing cells. These results corresponded with those obtained by transmission electron and immunofluorescence microscopies. This paper shows that endosymbiotic algae affect reduced mitochondrial number in the host P. bursaria significantly. [ABSTRACT FROM AUTHOR]

The effect of adrenaline in various concentrations and dopamine at a concentration of 10–10 mol/mL on the behavior of Paramecium caudatum was studied. It is shown that adrenaline reduces motor activity and changes the movement strategy of these protozoans; a dose-dependent behavioral response on the drug concentration was observed. This effect can be explained by the presence of adrenaline receptors located on the surface of the cell membrane. To study the direct effect of adrenaline on alpha and beta adrenergic receptors, the effect of non-selective adrenoblockers nicergoline and timolol is considered in this paper. At the same time, dopamine at a concentration of 10–10 mol/mL does not have a significant effect on the nature and magnitude of motor activity during the entire registration time, since this organism does not have receptors for this mediator. The proposed method makes it possible to quickly and objectively assess the nature of the effects of various pharmaceuticals acting on the catecholamine system. [ABSTRACT FROM AUTHOR]

This paper investigates the control of multi-agent systems inspired by chemotaxis of microorganisms. Chemotaxis is a biological phenomenon wherein organisms in an environment are attracted to food but move away from toxins. The problem addressed here is a formation control problem, i.e., a design problem of distributed controllers wherein the relative positions of agents become the desired positions with the progression of time. To solve this problem, we introduce a performance index that quantifies the achieved degree of a desired formation, and decompose it into local indices that can be embedded in the distributed controllers. Based on this, we propose formation controllers inspired by chemotaxis of Escherichia coli (E. coli), where each agent moves with the aim of increasing the corresponding local performance index using the chemotaxis controller of E. coli. In addition, to improve the accuracy of the resulting formation, we present Paramecium caudatum (P. caudatum)-type formation controllers by replacing the chemotaxis controller of E. coli used above with that of P. caudatum. The effectiveness is demonstrated by a comparison with the E. coli-type formation controllers via numerical simulation. This result implies that various chemotaxis controllers can be used in our method and the performance of the resulting controllers can be improved by choosing an appropriate chemotaxis controller. [ABSTRACT FROM AUTHOR]

Paramecium bursaria, a ciliated protist, forms a symbiotic relationship with the green alga Chlorella variabilis. This endosymbiotic association is a model system for studying the establishment of secondary symbiosis and interactions between the symbiont and its host organisms. Symbiotic algae reside in specialized compartments called perialgal vacuoles (PVs) within the host cytoplasm, which protect them from digestion by host lysosomal fusion. The relationship between P. bursaria and symbiotic Chlorella spp. is characterized by mutualism, in which both organisms benefit from this association. Furthermore, symbiotic algae also influence their host phenotypes, and algae-free P. bursaria can be obtained through various methods and reassociated with symbiotic algae, making it a valuable tool for studying secondary endosymbiosis. Recent advancements in genomic and transcriptomic studies on both hosts and symbionts have further enhanced the utility of this model system. This review summarizes the infection process of the symbiotic alga C. variabilis and its effects on the algal infection on number of host trichocysts, mitochondria, cytoplasmic crystals, total protein amount, stress responses, photoaccumulation, and circadian rhythms of the host P. bursaria. [ABSTRACT FROM AUTHOR]

In navigating to a better location, mobile organisms in diverse taxa change directions of travel occasionally, including bacteria, archaea, single-celled eukaryotes, and small nematode worms such as Caenorhabditis elegans. In perhaps the most common form of goal-orientated movement, the rate of such turns is adjusted in all these taxa to ascend (or descend) a chemical gradient. Basically, the rate of turns is reduced when the movement results in better conditions. In the bacterium Escherichia coli and in C. elegans, the turns are generated by random-rate processes, in which the probability of a turn occurring is constant at every moment. This is evidenced by a distribution of inter-turn intervals that has an exponential distribution. For the first time, we examined the distribution of inter-turn intervals in the single-celled eukaryote, Paramecium caudatum, in a class exercise for first-year university students. We found clear evidence for an exponential distribution of inter-turn intervals, implying a random-rate process in generating turns in Paramecium. The exercise also shows that university laboratory classes can be used to generate scientific data to address research questions whose answers are as yet unknown. [ABSTRACT FROM AUTHOR]

Replication of mitochondrial DNA in Paramecium aurelia involves the formation of a covalent crosslink at one end of this linear molecule and proceeds unidirectionally, producing a dimer consisting of two head to head monomers. The initiation regions within the dimer molecules have been sequenced and shown to be palindromic except for a central nonpalindromic A+T rich sequence, arranged in direct tandem repeats. This nonpalindromic region (see accompanying paper) has been identified as the cross-link which converts the initiation terminus into a continuous sequence. In this study, yeast transformation was used to assay the dimer initiation regions of P. aurelia mtDNA for the presence of autonomously replicating sequences. P. aurelia mtDNA fragments from species 1 and 4 were cloned into the yeast vector YIP5 and the hybrid plasmids (YPaM) were used to transform yeast. The dimer initiation regions from both species promoted high frequency transformation and extrachromosomal maintenance of YPaM plasmids. Subcloning analysis of the ARS-containing mtDNA fragments indicates, specifically, that the nonpalindrome, repetitive sequences are responsible for the autonomously replicating properties of YPaM plasmids. [ABSTRACT FROM AUTHOR]

Ocean internal waves appear as irregular bright and dark stripes on synthetic aperture radar (SAR) remote sensing images. Ocean internal waves detection in SAR images consequently constituted a difficult and popular research topic. In this paper, ocean internal waves are detected in SAR images by employing the faster regions with convolutional neural network features (Faster R-CNN) framework; for this purpose, 888 internal wave samples are utilized to train the convolutional network and identify internal waves. The experimental results demonstrate a 94.78% recognition rate for internal waves, and the average detection speed is 0.22 s/image. In addition, the detection results of internal wave samples under different conditions are analyzed. This paper lays a foundation for detecting ocean internal waves using convolutional neural networks. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) are essential for the viability of cells, while excess levels can be lethal by damaging proteins and nucleic acids. It is imperative to identify and elucidate the various cellular functions for which ROS molecules have a role. In this paper, the role of ROS in the regulation of ultradian rhythms in the ciliated protozoan Paramecium tetraurelia is examined. The frequency of spontaneous behavioral responses in Parameciun display a well-established ultradian rhythm with a periodicity of approximately 50–60 min. The artificial elevation of cytoplasmic ROS concentrations is shown to completely eliminate the rhythm in a reversible manner. Furthermore, the use of RNA interference techniques to knockdown the expression of superoxide dismutase, an enzyme that scavenges excess cytoplasmic ROS, also eliminates the ultradian rhythm. These data indicate that the concentration of ROS plays a role in the generation of the ultradian rhythm. A hypothesis is proposed for the generation of this ultradian rhythm that incorporates a role for ROS. [ABSTRACT FROM AUTHOR]

Tandem stop codons are extra stop codons hypothesized to be present downstream of genes to act as a backup in case of read-through of the real stop codon. Although seemingly absent from Escherichia coli, recent studies have confirmed the presence of such codons in yeast. In this paper we will analyze the genomes of two ciliate species— Paramecium tetraurelia and Tetrahymena thermophila—that reassign the stop codons TAA and TAG to glutamine, for the presence of tandem stop codons. We show that there are more tandem stop codons downstream of both Paramecium and Tetrahymena genes than expected by chance given the base composition of the downstream regions. This excess of tandem stop codons is larger in Tetrahymena and Paramecium than in yeast. We propose that this might be caused by a higher frequency of stop codon read-through in these species than in yeast, possibly because of a leaky termination machinery resulting from stop codon reassignment. [ABSTRACT FROM AUTHOR]

Holospora spp. and "Candidatus Gortzia infectiva", known as Holospora-like bacteria (HLB), are commonly found as nuclear endosymbionts of ciliates, especially the Paramecium genus. HLB are related by phylogenetic relationships, morphological features, and life-cycles, which involve two alternating morphotypes: reproductive and infectious forms (RF, IF). In this paper we describe a novel species belonging to the "Ca. Gortzia" genus, detected in P. multimicronucleatum, a ciliate for which infection by an HLB has not been reported, discovered in India. This novel endosymbiont shows unusual and surprising features with respect to other HLB, such as large variations in IF morphology and the occasional ability to reproduce in the host cytoplasm. We propose the name of "Candidatus Gortzia shahrazadis" for this novel HLB. Moreover, we report two additional species of HLB from Indian Paramecium populations: "Ca. Gortzia infectiva" (from P. jenningsi), and H. obtusa (from P. caudatum); the latter is the first record of Holospora from a tropical country. Although tropical, we retrieved H. obtusa at an elevation of 706m corresponding to a moderate climate not unlike conditions where Holospora are normally found, suggesting the genus Holospora does exist in tropical countries, but restricted to higher elevations. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) have excellent application prospects in various fields such as fluorescent dyes, but expanding their application, especially in bioimaging and the detection of organic pollutants, is still a major research objective. In this study, fluorescent CDs were successfully synthesized via the hydrothermal method using Serratia marcescens KMR-3. The platform based on CDs-KMR3 exhibited excellent stability, good biocompatibility, and low biotoxicity, and can be effectively applied to the imaging of bacteria, fungi, plant cells, protozoa and mammalian cells, and can specifically stain the membranes of all tested cells. In this study, for the first time, bacteria-derived CDs were used to image the representative species of organisms ranging from lower-order to higher-order organisms, thereby proving the feasibility of the application of CDs in the fluorescence imaging of Paramecium caudatum. Additionally, CDs-KMR3 can rapidly diffuse into all the parts of the leaf through diffusion into the veins and intercellular interstitium in response to the induction of transpiration. Moreover, the data illustrate that CDs-KMR3 are likely to enter the digestive tracts of microworms by ingestion through the oral cavity and pharynx, and spread to the pseudocoelom and somatic cells, and finally to be excreted from microworms through the anus. Furthermore, this platform can be utilized as fluorescent probes for the rapid and highly selective detection of p-nitrophenol (p-NP). Moreover, this study contributed to the increased application of bacteria-derived CDs in bioimaging and detection of p-NP. [ABSTRACT FROM AUTHOR]

Azo dyes are widely used in textile industries in variety of processes. Azo dyes are generally considered as xenobiotic chemicals because of their recalcitrant nature against biodegradation processes. However, in recent years, it has been considered that under specific environmental conditions many microorganisms are capable of converting these toxic azo dyes to non-colored compound or even completely mineralize them. The perspective of present study was to evaluate the decolorizing efficiency of newly isolated Paramecium species in textile industrial wastewater containing azo dyes. This efficiency was assessed by determining the level of stress biomarkers such as GSH, GST, CAT, SOD, and GPx in the ciliates. Under optimum conditions of temperature and pH, RR2 azo dyes have 90.86 and 90.37% decolorization by P. jenningsi and P. multimicronucleatum, respectively. The azo dye degraded products were analyzed by using Fourier transformed infrared spectroscopy (FTIR). Morphology of Paramecium species was analyzed under light microscope after exposure to azo dye. GSH contents were significantly decreased while activities of antioxidant enzymes such as GST, CAT, SOD, and GPx were significantly increased as compared to control. As a result, Paramecium seems to be potentially useful for bioremediation of textile-dying industry effluents. [ABSTRACT FROM AUTHOR]

There are a wide range of student emotions in academic settings, but apart from emotions such as interest and well-being, disgust is a negative emotion which might be relevant in biology education, for instance, during dissection or when encountering living animals. This paper addresses the issue of situational disgust during a course at the university using living animals and prepared mounts. The course covers a wide range of organisms from protists (e.g.Paramecium) through invertebrates to vertebrates and uses many methods (e.g. microscopy, dissection, and behavioral observations) and specific content (anatomy, structure, and behavior). The dissection of the trout was rated as most disgusting, followed by working with living woodlice, living earthworms, and living snails. The least disgusting lessons were those dealing with microscopy, mammalian skulls, honeybee dance, and bird flight. Based on animals, macro-invertebrates were rated as most disgusting and mammals as least disgusting. Concerning methods, observing through a microscope was perceived as being least disgusting, followed by experiments without animals, then followed by experiments with living animals and, most disgusting, dissection. Disgust was correlated negatively with interest, well-being, and competence but positively with pressure and boredom. Thus, low disgust is related to high interest, well-being, and competence, while higher disgust is related to higher pressure and boredom. The results show a need for measuring situational disgust in addition to survey studies. They also suggest that perceived disgust negatively affects intrinsic motivation. This has implications for biology teaching, because carrying out dissections or experiencing living animals in the classroom may have a detrimental effect on motivation. [ABSTRACT FROM AUTHOR]

In this paper we assess the role of the protein MKS1 (Meckel syndrome type 1) in the cortical membrane mechanics of the ciliated protist Paramecium. This protein is known to be crucial in the process of cilium formation, and we investigate its putative role in membrane--cytoskeleton attachment. Therefore, we compare cells where the gene coding for MKS1 is silenced to wild-type cells. We found that scanning electron microscopy observation of the cell surface reveals a cup-like structure in wild-type cells that is lost in silenced cells. Since this structure is based on the underlying cytoskeleton, one hypothesis to explain this observation is a disruption of membrane attachment to the cytoskeleton in the absence of MKS1 that should affect plasma membrane mechanics. We test this by probing the mechanics of wild-type and silenced cells by micropipette aspiration. Strikingly, we observe [ABSTRACT FROM AUTHOR]

Small planktonic organisms ubiquitously display unsteady or impulsive motion to attack a prey or escape a predator in natural environments. Despite this, the role of unsteady forces such as history and added mass forces on the low-Reynolds-number propulsion of small organisms, e.g. Paramecium, is poorly understood. In this paper, we derive the fundamental equation of motion for an organism swimming by means of the surface distortion in a non-uniform background flow field at a low-Reynolds-number regime. We show that the history and added mass forces are important as the product of Reynolds number and Strouhal number increases above unity. Our results for an unsteady squirmer show that unsteady inertial effects can lead to a non-zero mean velocity for the cases with zero streaming parameters, which have zero mean velocity in the absence of inertia. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Some Paramecium species are common research objects in various fields of science. • At the same time, the biodiversity structure of the others is almost unknown. • Here we present a molecular analysis of 60 Cypriostomum strains. • Three main clades has been revealed, each one with internal sub-clusters. • Their occurence reflects a separation into morphospecies and cryptic species. Abstract Although some Paramecium species are suitable research objects in many areas of life sciences, the biodiversity structure of other species is almost unknown. In the current survey, we present a molecular analysis of 60 Cypriostomum strains, which for the first time allows for the study of intra- and interspecific relationships within that subgenus, as well as the assessment of the biogeography patterns of its morphospecies. Analysis of COI mtDNA variation revealed three main clades (separated from each other by approximately 130 nucleotide substitutions), each one with internal sub-clusters (differing by 30 to 70 substitutions – a similar range found between P. aurelia cryptic species and P. bursaria syngens). The first clade is represented exclusively by P. polycaryum ; the second one includes only four strains identified as P. calkinsi. The third cluster seems to be paraphyletic, as it includes P. nephridiatum , P. woodruffi , and Eucandidatus P. hungarianum. Some strains, previously identified as P. calkinsi , had COI sequences identical or very similar to P. nephridiatum ones. Morphological reinvestigation of several such strains revealed common morphological features with P. nephridiatum. The paper contains new information concerning speciation within particular species, i.e. existence of cryptic species within P. polycaryum (three) and in P. nephridiatum (six). [ABSTRACT FROM AUTHOR]

Paramecium tetraurelia displays a behavioral response to environmental stimuli that involves changes in the direction and speed of swimming. This paper demonstrates that there are periodic variations in the frequency of behavioral responses of individual cells. The frequency of the backward swimming response undergoes repeated oscillations with a period (tau) between 40 and 50 minutes; these oscillations are only slightly affected by the temperature at which the cells have been grown. These data indicate the presence of an ultradian clock that underlies this cellular process. However, growing cells in the presence of low concentrations of LiCl perturbs the ultradian rhythm, with the periodicity being reduced to approximately 11 minutes. The LiCl effect is seen within 10-45 minutes, depending on the concentration of LiCl used, and is completely reversible. In order to determine if the LiCl effect was due to a depletion of inositol, cells were grown in 10 mM myo-inositol for 24 hours prior to the addition of LiCl. It was found that the presence of excess inositol inhibited the perturbation of the periodicity caused by the LiCl. These results signify that Paramecium tetraurelia possesses an endogenous ultradian clock that influences the strength of the behavioral response, and the inositol signaling pathway is most likely involved in the generation of the ultradian rhythm. Therefore, the Paramecium behavioral response is an excellent model system for elucidation of the molecular mechanisms underlying the ultradian rhythms. [ABSTRACT FROM AUTHOR]

The heavy metal cadmium is a dangerous environmental toxicant that can be lethal to humans and other organisms. This paper demonstrates that cadmium is lethal to the ciliated protozoan Paramecium tetraurelia and that a circadian clock modulates the sensitivity of the cells to cadmium. Various concentrations of cadmium were shown to increase the number of behavioral responses, decrease the swimming speed of cells, and generate large vacuole formation in cells prior to death. Cells were grown in either 12-h light/12-h dark or constant dark conditions exhibited a toxic response to 500 μM CdCl2; the sensitivity of the response was found to vary with a 24-h periodicity. Cells were most sensitive to cadmium at circadian time 0 (CT0), while they were least sensitive in the early evening (CT12). This rhythm persisted even when the cells were grown in constant dark. The oscillation in cadmium sensitivity was shown to be temperature-compensated; cells grown at 18°C and 28°C had a similar 24-h oscillation. Finally, phase shifting experiments demonstrated a phase-dependent response to light. These data establish the criteria required for a circadian clock and demonstrate that P. tetraurelia possesses a circadian-influenced regulatory component of the cadmium toxic response. The Paramecium system is shown to be an excellent model system for the study of the effects of biological rhythms on heavy metal toxicity. [ABSTRACT FROM AUTHOR]

It has been reported that Paramecium proliferates faster when cultured under microgravity in orbit, and slower when cultured under hypergravity. This shows that the proliferation rate of Paramecium affected by gravity. The effect of gravity on Paramecium proliferation has been argued to be direct in a paper with an axenic culture under hypergravity. To clear up uncertainties with regard to the effect of gravity, Paramecium tetraurelia was cultured axenically under hypergravity (20 × g) and the time course of the proliferation was investigated quantitatively by a new non-invasive method, laser-beam optical slice, for measuring the cell density. This method includes optical slicing a part of the culture and computer-aided counting of cells in the sliced volume. The effects of hypergravity were assessed by comparing the kinetic parameters of proliferation that were obtained through a numerical analysis based on the logistic growth equation. Cells grown under 20 × g conditions had a significantly lower proliferation rate, and had a lower population density at the stationary phase. The lowered proliferation rate continued as long as cells were exposed to hypergravity (> one month). Hypergravity reduced the cell size of Paramecium. The long and short axes of the cell became shorter at 20 x g than those of control cells, which indicates a decrease in volume of the cell grown under hypergravity and is consistent with the reported increase in cell volume under microgravity. The reduced proliferation rate implies changes in biological time defined by fission age. In fact the length of autogamy immaturity decreased by measure of clock time, whereas it remained unchanged by measure of fission age. [ABSTRACT FROM AUTHOR]

This paper investigates the possibility as to whether protozoa can be treated as a living micro manipulator/actuator. Motion control of protozoa is made by using the negative galvanotaxis. First, a basic property test with a DC electric field showed that the Paramecium could be controlled by the electrical potential gradient. By using the eight-direction carbon electrode pool (4 mm electrode distance and 0.2 mm thickness), the operator can control the Paramecium in the aiming direction. Automatic motion control of protozoa is also achieved by using the image processing technology and fuzzy control method. The control method for rapid turning is also developed. To adopt this method to the automatic motion control program, Paramecium can be controlled along any shaped guide route. The actuation to rotate the micro-impeller (0.5 mm diameter) is achieved by Paramecium. These facts show that protozoa are able to be used as a micro manipulator/actuator [ABSTRACT FROM PUBLISHER]

Plant-infecting RNA viruses from 30 families and floating genera, as well as a great number of uncultured as yet-unclassified plant-associated viruses have been described. Even so, the plant RNA virosphere is still underexplored. RNA extracted from enriched virus particles of 50 L water samples from the Teltow Canal and the Havel River in Berlin, Germany, was sequenced using Illumina next-generation sequencing. Sequences were searched for plant viruses with BLAST and DIAMOND. Phylogenetic analyses were conducted with IQ-TREE 2. Altogether, 647 virus sequences greater than 1 kb were detected and further analyzed. These data revealed the presence of accepted and novel viruses related to Albetovirus, Alphaflexiviridae, Aspiviridae, Bromoviridae, Endornaviridae, Partitiviridae, Potyviridae, Solemoviridae, Tombusviridae and Virgaviridae. The vast majority of the sequences were novel and could not be taxonomically assigned. Several tombus- and endorna-like viruses make use of alternative translation tables that suggest unicellular green algae, ciliates, or diplomonades as their hosts. The identification of 27 albeto-like satellite viruses increases available sequence data five-fold. Sixteen new poty-like viruses align with other poty-like viruses in a link that combines the Astroviridae and Potyviridae families. Further, the identification of viruses with peptidase A6-like and peptidase A21-like capsid proteins suggests horizontal gene transfer in the evolution of these viruses. [ABSTRACT FROM AUTHOR]

This study investigated the interaction of inorganic aqueous Eu(III), Pb(II), and U(VI) with Paramecium sp., a representative single-celled protozoan that lives in freshwater. Living and prekilled Paramecium cells were tested. The prekilled cells were killed with a fixative. After 24 h exposure of the cells to inorganic aqueous solutions containing Eu(III) or U(VI), analyses by microparticle-induced X-ray emission with a focused beam (<1 μm) did not detect Eu and U in the living cells, whereas Eu and U were detected in the prekilled cells. Size exclusion chromatography coupled with on-line ultraviolet–visible detection and elemental detection by inductively coupled plasma mass spectrometry of the aqueous phases collected after the living cell experiments revealed that a fraction of the Eu, Pb, and U in the aqueous phase bound to a large ( ca . 250 kDa) Paramecium biomolecule and formed a metal-organic complex. The characteristics of the biomolecule were consistent with those of the soluble glycoproteins covering the surfaces of Paramecium cells. These results show that Paramecium cells transform inorganic aqueous Eu, Pb, and U to organic complexes. This paper discusses the relation between this novel complexation and the sorption of these heavy elements on Paramecium cells. [ABSTRACT FROM AUTHOR]

Centrins are highly conserved, ubiquitous cytoskeletal components which belong to the EF-hand superfamily of Ca2+-modulated proteins. We report here the molecular characterization of new members of the centrin family, Paramecium centrins. Previous studies described the organization of the infraciliary lattice (ICL), the innermost cortical cytoskeletal network of Paramecium, and showed that it was composed of a set of low-molecular-mass, Ca2+-binding polypeptides [Garreau de Loubresse, N., Klotz, C., Vigues, B., Rutin, J & Beisson, J. (1991) Biol. Cell 71, 217-225]. In this paper we show that these polypeptides are recognized by specific anti-centrin polyclonal antibodies. Their microsequences revealed four distinct N-termini. For one of them, ICL1, N-terminal and internal peptide sequences were used for PCR amplification and cloning of a DNA fragment containing a complete centrin coding sequence. The deduced amino acid sequence presents about 50% identify with those of centrins from other species. Further molecular analysis allowed us to identify two additional closely related, co-expressed ICL1 genes, providing the first example of a centrin multigenic family in a microorganism. [ABSTRACT FROM AUTHOR]

Ciliates are highly differentiated cells which display extensive deployment of microtubular systems. Because genetic diversity of tubulin is extremely reduced in these cells, microtubule diversity is mostly generated at the post-translational level either through direct modification of tubulin or through the binding of associated proteins to microtubules. We have undertaken a systematic exploration of microtubule diversity in ciliates by way of production of monoclonal antibodies. Previously we reported the biochemical characterization of these antibodies. In addition to antibodies directed against primary sequences, we obtained antibodies directed against post-translational modifications. In this paper, we report a detailed analysis of the distribution of the various epitopes on the microtubular networks of Paramecium, both in interphase cells and during division morphogenesis. Each of these antibodies decorates a subset of microtubules. Acetylation, recognized by antibodies TEU 318 and TEU 348, is detected on stable microtubules early after microtubule assembly. Epitopes recognized by two other antibodies (TAP 952 and AXO 58) are found on a subset of stable microtubules; in addition, the TAP 952 antibody is also found on labile microtubules; both epitopes are detected as soon as microtubule assembly occurs. In contrast, the epitope of the antibody, AXO 49, is associated with only a restricted subset of stable microtubules in the interphase cell, and is detected a lag-time after microtubule assembly during division morphogenesis. These data show that microtubule diversity is generated through a time-dependent sequence and according to a definite spatial pattern. [ABSTRACT FROM AUTHOR]

Ciliated protists are highly differentiated unicellular eukaryotes that possess special sexual processes (conjugation and autogamy) that rely on their unique nuclear dimorphism, i.e., the presence of both a germline micronucleus (MIC) and a somatic macronucleus (MAC) in a single cell. The sexual processes show a high diversity in different ciliates. To better understand the differentiation and evolution of sexual processes in closely related species, we investigated the nuclear events during conjugation in Paramecium jenningsi strain GZ, a poorly studied close relative of the well-known P. aurelia complex. The main results include: (1) the conjugation process takes about 48 h, including three prezygotic divisions (meiosis I, II, and mitosis) and three postzygotic divisions; (2) the MICs are dominated by the "parachute" phase at the prophase of meiosis I; (3) after meiosis II, a variable number of nuclei undergo the third prezygotic division, and the two products near the paroral cone become the genetically identical migratory and stationary pronuclei; (4) the synkaryon divides three times to form the MIC and the MAC anlagen, but only one nuclear product of the first postzygotic division completes the next two divisions; and (5) an extra cell division is required to complete the last step of conjugation, during which two MIC anlagen undergo mitotic division while two MAC anlagen are distributed between the daughter cells without division. The comparison of the nuclear events during conjugation in representatives of the class Oligohymenophorea reveals that usually there are three prezygotic divisions and a variable number of postzygotic divisions. However, the number of selected and differentiated nuclei after each division differs among species. This study provided a new model ciliate for further investigations of nuclear selection and differentiation as well as nuclear morphology during meiosis. [ABSTRACT FROM AUTHOR]

Material-based tactics have attracted extensive attention in driving the functional evolution of organisms. In aiming to design steerable bioartificial organisms to scavenge pathogenic waterborne viruses, we engineer Paramecium caudatum (Para), single-celled microorganisms, with a semiartificial and specific virus-scavenging organelle (VSO). Fe3O4 magnetic nanoparticles modified with a virus-capture antibody (MNPs@Ab) are integrated into the vacuoles of Para during feeding to produce VSOs, which persist inside Para without impairing their swimming ability. Compared with natural Para, which has no capture specificity and shows inefficient inactivation, the VSO-engineered Para (E-Para) specifically gathers waterborne viruses and confines them inside the VSOs, where the captured viruses are completely deactivated because the peroxidase-like nano-Fe3O4 produces virus-killing hydroxyl radicals (•OH) within acidic environment of VSO. After treatment, magnetized E-Para is readily recycled and reused, avoiding further contamination. Materials-based artificial organelles convert natural Para into a living virus scavenger, facilitating waterborne virus clearance without extra energy consumption. The material-based evolution of organisms has attracted broad interdisciplinary interest, however, the fabrication of material-integrated organelles remains inadequately exploited. Here the authors engineer a bioartificial organism by integrating a semiartificial and specific virus-scavenging organelle to scavenge pathogenic waterborne viruses. [ABSTRACT FROM AUTHOR]

Paramecium tetraurelia is the most vulnerable freshwater ciliated protest to the pesticide-contaminated aquatic environment and is commonly used as a valuable biological model in studies investigating the monitoring of environmental quality. The present study was undertaken to screen the physiological, biochemical, and antioxidant responses of Paramecium tetraurelia. exposed to chlorpyrifos-ethyl (an insecticide). Paramecia received increasing concentrations of chlorpyrifos ethyl (0.04, 0.05, 0.06 and 0.07 mg/L) for 24, 48, 72 and 96h. Results revealed concentration- and time-dependent variations in growth and response percentage in exposed cells. In addition, protein and malondialdehyde levels and catalase activity were significantly increased in a concentration-dependent manner in treated cells compared with controls. However, the enzymatic activity of acetylcholinesterase and glutathione level showed a concentration-dependent decrease in treated paramecium cells compared with controls. In conclusion, chlorpyrifos-ethyl, especially at higher concentrations, proved to induce marked changes in the physiological and antioxidant profiles of Paramecium tetraurelia. which are promised to be used as an efficient monitoring organism for environmental water pollutants. [ABSTRACT FROM AUTHOR]

Many heterotrophic microbial eukaryotes are size‐selective feeders. Some microorganisms increase their size by forming multicellular colonies. We used choanoflagellates, Salpingoeca helianthica, which can be unicellular or form multicellular colonies, to study the effects of multicellularity on vulnerability to predation by the raptorial protozoan predator, Amoeba proteus, which captures prey with pseudopodia. Videomicrography used to measure the behavior of interacting S. helianthica and A. proteus revealed that large choanoflagellate colonies were more susceptible to capture than were small colonies or single cells. Swimming colonies produced larger flow fields than did swimming unicellular choanoflagellates, and the distance of S. helianthica from A. proteus when pseudopod formation started was greater for colonies than for single cells. Prey size did not affect the number of pseudopodia formed and the time between their formation, pulsatile kinematics and speed of extension by pseudopodia, or percent of prey lost by the predator. S. helianthica did not change swimming speed or execute escape maneuvers in response to being pursued by pseudopodia, so size‐selective feeding by A. proteus was due to predator behavior rather than prey escape. Our results do not support the theory that the selective advantage of becoming multicellular by choanoflagellate‐like ancestors of animals was reduced susceptibility to protozoan predation. [ABSTRACT FROM AUTHOR]

Due to the high frequency at which sugar is found in foods, adolescents can build addictive tendencies to sugar. The sweet compound is often associated with positive mindsets and memories. To collect data on how different sugar levels may impact mood, we administered surveys before and after female participants aged 14-17 consumed cookies of varying sugar content (8, 4, and 0 grams of sugar/cookie). In response to the question, “rate your current mood on a scale of 1-10,” participants reported a significantly higher mood following consumption of the 8g and 4g cookies (p=0.0001 and p=0.0013, respectively) and a substantially lower mood following consumption of the 0g cookie (p=0.0405). Interestingly, sugar content did not affect how much participants reported they would pay for each cookie (p=0.3842). These results suggest that sugar content impacts mood; however, it did not significantly affect the value that participants placed on the reward of each cookie. [ABSTRACT FROM AUTHOR]

The ciliate Paramecium bursaria harbors several hundred symbiotic algae in its cell and is widely used as an experimental model for studying symbiosis between eukaryotic cells. Currently, various types of bacteria and eukaryotic microorganisms are used as food for culturing P. bursaria; thus, the cultivation conditions are not uniform among researchers. To unify cultivation conditions, we established cloned, unfed strains that can be cultured using only sterile medium without exogenous food. The proliferation of these unfed strains was suppressed in the presence of antibiotics, suggesting that bacteria are required for the proliferation of the unfed strains. Indeed, several kinds of bacteria, such as Burkholderiales, Rhizobiales, Rhodospirillales, and Sphingomonadales, which are able to fix atmospheric nitrogen and/or degrade chemical pollutants, were detected in the unfed strains. The genetic background of the individually cloned, unfed strains were the same, but the proliferation curves of the individual P. bursaria strains were very diverse. Therefore, we selected multiple actively and poorly proliferating individual strains and compared the bacterial composition among the individual strains using 16S rDNA sequencing. The results showed that the bacterial composition among actively proliferating P. bursaria strains was highly homologous but different to poorly proliferating strains. Using unfed strains, the cultivation conditions applied in different laboratories can be unified, and symbiosis research on P. bursaria will make great progress. [ABSTRACT FROM AUTHOR]

Paramecium is a large unicellular organism that swims in fresh water using cilia. When stimulated by various means (mechanically, chemically, optically, thermally), it often swims backward then turns and swims forward again in a new direction: this is called the avoiding reaction. This reaction is triggered by a calcium-based action potential. For this reason, several authors have called Paramecium the "swimming neuron". Here we present an empirically constrained model of its action potential based on electrophysiology experiments on live immobilized paramecia, together with simultaneous measurement of ciliary beating using particle image velocimetry. Using these measurements and additional behavioral measurements of free swimming, we extend the electrophysiological model by coupling calcium concentration to kinematic parameters, turning it into a swimming model. In this way, we obtain a model of autonomously behaving Paramecium. Finally, we demonstrate how the modeled organism interacts with an environment, can follow gradients and display collective behavior. This work provides a modeling basis for investigating the physiological basis of autonomous behavior of Paramecium in ecological environments. Author summary: Behavior depends on a complex interaction between a variety of physiological processes, the body and the environment. We propose to examine this complex interaction in an organism consisting of a single excitable and motile cell, Paramecium. The behavior of Paramecium is based on trial and error: when it encounters an undesirable situation, it backs up and changes direction. This avoiding reaction is triggered by an action potential. Here we developed an empirically constrained biophysical model of Paramecium's action potential, which we then coupled to its kinematics. We then demonstrate the potential of this model in investigating various types of autonomous behavior, such as obstacle avoidance, gradient-following and collective behavior. [ABSTRACT FROM AUTHOR]

Protozoa, in both humans and animals, are one of the leading causes of disease. International programmes introduced in many countries have helped reduce the incidence of disease. However, it has recently become increasingly difficult to achieve the goals set for the coming years. One of the main reasons for this, as with other pathogenic organisms, such as bacteria and fungi, is the increasing resistance to current methods of treating and preventing infection. Therefore, new therapies with high efficacy are needed. In the present study, the novel mixtures of essential oils (EOs), clove, garlic, Ceylon cinnamon, and rosemary with organic acids (acetic, propionic, lactic) and metal ions (Cu, Mn, Zn) were tested against five selected model protozoa (Euglena gracilis, Gregarina blattarum, Amoeba proteus, Paramecium caudatum, Pentatrichomonas hominis). The cytotoxicity and potential anticancer activity of the obtained combinations were tested on the human fibroblasts (NHDF) and human cancer cell lines (A549, MCF7, LoVo, HT29). All of the mixtures showed very good antiprotozoal properties. The most efficient were the combination of clove and rosemary essential oils, mixtures of acids, and Mn ions. The LD50 values were in the range of 0.001–0.006% and the LD100 values were 0.002–0.008%. All of the tested mixtures did not show cytotoxicity against normal cells, but did show growth inhibition against cancer cell lines. The most cytotoxic against cancer cells were combinations with cinnamon essential oil. Nevertheless, the proposed combinations containing essential oils, organic acids, and metal ions have high antiprotozoal activity, with low toxicity to healthy human cells. [ABSTRACT FROM AUTHOR]

Fertilization-initiated development and adult-onset aging are standard features in the life history of eukaryotes. In Paramecium, the number of cell divisions after the birth of a new generation is an essential parameter of sexual phase transition and aging. However, the gene driving this process and its evolutionary origin have not yet been elucidated. Here we report several critical outcomes obtained by molecular genetics, immunofluorescence microscopy, transformation by microinjection, and enzymological analysis. The cloned immaturin gene induces sexual rejuvenation in both mature and senescent cells by microinjection. The immaturin gene originated from proteobacteria's glutathione-S-transferase (GST) gene. However, immaturin has been shown to lose GST activity and instead acquire nuclease activity. In vitro substrates for immaturin-nuclease are single- and double-stranded DNA, linear and circular DNA, and single-stranded viral genome RNA such as coronavirus. Anti-immaturin antibodies have shown that the subcellular localizations of immaturin are the macronucleus, cytoplasm, cell surface area, and cilia. The phase transition of sexuality is related to a decrease in the intracellular abundance of immaturin. We propose that sexual maturation and rejuvenation is a process programmed by the immaturin gene, and the sexual function of each age is defined by both the abundance and the intracellular localization mode of the immaturin-nuclease. [ABSTRACT FROM AUTHOR]

The study of comparative cognition bloomed in the 1970s and 1980s with a focus on representations in the heads of animals that undergird what animals can achieve. Even in action-packed domains such as navigation and spatial cognition, a focus on representations prevailed. In the 1990s, I suggested a conception of navigation in terms of navigational servomechanisms. A servomechanism can be said to aim for a goal, with deviations from the goal-directed path registering as an error. The error drives action to reduce the error in a negative-feedback loop. This loop, with the action reducing the very signal that drove action in the first place, is key to defining a servomechanism. Even though actions are crucial components of servomechanisms, my focus was on the representational component that encodes signals and evaluates errors. Recently, I modified and amplified this view in claiming that, in navigation, servomechanisms operate by modulating the performance of oscillators, endogenous units that produce periodic action. The pattern is found from bacteria travelling micrometres to sea turtles travelling thousands of kilometres. This pattern of servomechanisms working with oscillators is found in other realms of cognition and of life. I think that oscillators provide an effective way to organise an organism's own activities while servomechanisms provide an effective means to adjust to the organism's environment, including that of its own body. [ABSTRACT FROM AUTHOR]

Flagella enable bacteria to actively spread within the environment. A number of species possess two separate flagellar systems, where in most cases a primary polar flagellar system is supported by distinct secondary lateral flagella under appropriate conditions. Using functional fluorescence tagging on one of these species, Shewanella putrefaciens, as a model system, we explored how two different flagellar systems can exhibit efficient joint function. The S. putrefaciens secondary flagellar filaments are composed as a mixture of two highly homologous non‐glycosylated flagellins, FlaA2 and FlaB2. Both are solely sufficient to form a functional filament, however, full spreading motility through soft agar requires both flagellins. During swimming, lateral flagella emerge from the cell surface at angles between 30° and 50°, and only filaments located close to the cell pole may form a bundle. Upon a directional shift from forward to backward swimming initiated by the main polar flagellum, the secondary filaments flip over and thus support propulsion into either direction. Lateral flagella do not inhibit the wrapping of the polar flagellum around the cell body at high load. Accordingly, screw thread‐like motility mediated by the primary flagellum and activity of lateral flagella cumulatively supports spreading through constricted environments such as polysaccharide matrices. [ABSTRACT FROM AUTHOR]

The accumulation of different photosensitizers (PSs) (Radachlorin, Rose Bengal, Coproporphyrin) in ciliates Paramecium caudatum and amoebae Amoeba proteus were evaluated both by observations on living cells and on the fixed material, using fluorescence and confocal laser scanning microscopy. The above single-celled eukaryotic organisms shared similar intracellular distribution patterns of different PSs with mammalian cells and thus can be used as model objects at the initial stages of preclinical studies of various substances, potential PSs. Some methodological recommendations for the identification of intracellular compartments, where PSs selectively accumulate, were proposed. [ABSTRACT FROM AUTHOR]

Giant viruses are a large group of viruses that infect many eukaryotes. Although components that do not obey the overall icosahedral symmetry of their capsids have been observed and found to play critical roles in the viral life cycles, identities and high-resolution structures of these components remain unknown. Here, by determining a near-atomic-resolution, five-fold averaged structure of Paramecium bursaria chlorella virus 1, we unexpectedly found the viral capsid possesses up to five major capsid protein variants and a penton protein variant. These variants create varied capsid microenvironments for the associations of fibers, a vesicle, and previously unresolved minor capsid proteins. Our structure reveals the identities and atomic models of the capsid components that do not obey the overall icosahedral symmetry and leads to a model for how these components are assembled and initiate capsid assembly, and this model might be applicable to many other giant viruses. Giant viruses are large DNA viruses with capsid diameters up to 500 nm. Given technical challenges only few high-resolution structures of viral capsids exist. Here, Shao et al. provide a nearatomic structure of giant virus PBCV-1 capsid and resolve the previously unknown asymmetric capsid components. The local capsid microenvironments created by these components provide insights into the mechanism of capsid assembly of giant viruses. [ABSTRACT FROM AUTHOR]

Calcium (Ca2+) is a universal second messenger that plays a key role in cellular signaling. However, Ca2+ signals are transduced with the help of Ca2+-binding proteins, which serve as sensors, transducers, and elicitors. Among the collection of these Ca2+-binding proteins, calmodulin (CaM) emerged as the prototypical model in eukaryotic cells. This is a small protein that binds four Ca2+ ions and whose functions are multiple, controlling many essential aspects of cell physiology. CaM is universally distributed in eukaryotes, from multicellular organisms, such as human and land plants, to unicellular microorganisms, such as yeasts and ciliates. Here, we review most of the information gathered on CaM in Paramecium, a group of ciliates. We condense the information here by mentioning that mature Paramecium CaM is a 148 amino acid-long protein codified by a single gene, as in other eukaryotic microorganisms. In these ciliates, the protein is notoriously localized and regulates cilia function and can stimulate the activity of some enzymes. When Paramecium CaM is mutated, cells show flawed locomotion and/or exocytosis. We further widen this and additional information in the text, focusing on genomic data. [ABSTRACT FROM AUTHOR]

Understanding why various organisms evolve alternative ways of living requires information on both the fitness advantages of phenotypic modifications and the costs of constructing and operating cellular features. Although the former has been the subject of a myriad of ecological studies, almost no attention has been given to how organisms allocate resources to alternative structures and functions. We address these matters by capitalizing on an array of observations on diverse ciliate species and from the emerging field of evolutionary bioenergetics. A relatively robust and general estimator for the total cost of a cell per cell cycle (in units of ATP equivalents) is provided, and this is then used to understand how the magnitudes of various investments scale with cell size. Among other things, we examine the costs associated with the large macronuclear genomes of ciliates, as well as ribosomes, various internal membranes, osmoregulation, cilia, and swimming activities. Although a number of uncertainties remain, the general approach taken may serve as blueprint for expanding this line of work to additional traits and phylogenetic lineages. [ABSTRACT FROM AUTHOR]

The term epigenetics is used for any layer of genetic information aside from the DNA base‐sequence information. Mammalian epigenetic research increased our understanding of chromatin dynamics in terms of cytosine methylation and histone modification during differentiation, aging, and disease. Instead, ciliate epigenetics focused more on small RNA‐mediated effects. On the one hand, these do concern the transport of RNA from parental to daughter nuclei, representing a regulated transfer of epigenetic information across generations. On the other hand, studies of Paramecium, Tetrahymena, Oxytricha, and Stylonychia revealed an almost unique function of transgenerational RNA. Rather than solely controlling chromatin dynamics, they control sexual progeny's DNA content quantitatively and qualitatively. Thus epigenetics seems to control genetics, at least genetics of the vegetative macronucleus. This combination offers ciliates, in particular, an epigenetically controlled genetic variability. This review summarizes the epigenetic mechanisms that contribute to macronuclear heterogeneity and relates these to nuclear dimorphism. This system's adaptive and evolutionary possibilities raise the critical question of whether such a system is limited to unicellular organisms or binuclear cells. We discuss here the relevance of ciliate genetics and epigenetics to multicellular organisms. [ABSTRACT FROM AUTHOR]

Primary (eukaryote and procaryote) and secondary (eukaryote and eukaryote) endosymbioses are driving forces in eukaryotic cell evolution. These phenomena are still contributing to acquire new cell structures and functions. To understand mechanisms for establishment of each endosymbiosis, experiments that can induce endosymbiosis synchronously by mixing symbionts isolated from symbiont‐bearing host cells and symbiont‐free host cells are indispensable. Recent progress on endosymbiosis using Paramecium and their endonuclear symbiotic bacteria Holospora or symbiotic green alga Chlorella has been remarkable, providing excellent opportunities for elucidating host–symbiont interactions. These organisms are now becoming model organisms to know the mechanisms for establishing primary and secondary endosymbioses. Based on experiments of many researchers, we introduce how these endosymbionts escape from the host lysosomal fusion, how they migrate in the host cytoplasm to localize specific locations within the host, how their species specificity and strain specificity of the host cells are controlled, how their life cycles are controlled, how they escape from the host cell to infect more young host cell, how they affect the host viability and gene expression, what kind of substances are needed in these phenomena, and what changes had been induced in the symbiont and the host genomes. [ABSTRACT FROM AUTHOR]