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Cells of Paramecium aurelia labeled with tritiated thymidine were irradiated with ultraviolet light and then were either exposed to photoreactivating light or kept in the dark as controls. In the controls, the level of thymine-containing pyrimidine dimers did not change, but in cells exposed to photoreactivating light such dimers were destroyed. This is the first demonstration in a eukaryote of in vivo photoreactivation of thymine-containing pyrimidine dimers.

The ciliate Paramecium bursaria possesses cell organelles called trichocysts that have defensive functions. Paramecium bursaria is capable of symbiosis with Chlorella variabilis, and the symbiotic algae are situated in close proximity to the trichocysts. To clarify the relationship between trichocysts in P. bursaria and the presence or absence of the intracellular symbiotic C. variabilis, this study compared the regeneration capacity of trichocysts in alga-free and algae-bearing P. bursaria. In addition, trichocyst protein abundance was measured when alga-free P. bursaria specimens were artificially infected with Chlorella. After completely removing trichocysts from P. bursaria cells by treatment with lysozyme and observing them after 24 h, the percentage of regenerating trichocysts in the entire cell was significantly higher in alga-free cells than that in algae-bearing cells. We also developed a simple method for the isolation of high-purity trichocysts to quantify trichocyst protein amounts. There was a significant difference in the trichocyst protein abundance of P. bursaria before and one week after mixing with Chlorella (i.e., after the establishment of symbiosis with algae). This study shows the importance of trichocysts in alga-free P. bursaria as well as their competition with symbiotic C. variabilis for attachment sites during the algal infection process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier GmbH. All rights reserved.)

Raphidiopsis blooms are notorious for cyanotoxin formation and strong invasiveness, threatening the stability of aquatic ecosystems and human health. The protozoa Paramecium can potentially serve as an organism for controlling Raphidiopsis blooms owing to its grazing effect. However, the grazing ability of Paramecium is largely determined by the size of the prey, and the population of Raphidiopsis consists of filaments of varying lengths and sizes. The selective grazing behavior of Paramecium toward short-length or small-sized filaments in the Raphidiopsis population, as opposed to long filaments, remains unclear. Therefore, in this study, we co-cultured the predator Paramecium sp. with different initial abundances and the prey Raphidiopsis raciborskii to explore this knowledge gap. Our results suggested that: (1) the population of R. raciborskii declined under the selective grazing effect of Paramecium sp. on short filaments, whereas R. raciborskii with long filaments survived; (2) the growth of Paramecium sp. feeding on the same abundance of R. raciborskii was reduced at higher initial abundances, whereas its carrying capacity exhibited an opposite trend; (3) under ingestion by Paramecium sp., the morphology of R. raciborskii developed in the direction of becoming larger, and higher initial abundances of Paramecium sp. intensified this process; (4) increasing initial abundance of Paramecium sp. aggravated the decline of R. raciborskii photosynthetic activity. Therefore, the grazing effect of Paramecium sp. on R. raciborskii mainly affects filaments of short length or small size. Collectively, these results clarify the inter-species interaction between the protozoa Paramecium and filamentous cyanobacteria Raphidiopsis, including population dynamics and morphological and physiological changes in the predator and prey. Such insights into the interactions between Paramecium and R. raciborskii may have implications for the biological control of blooms caused by filamentous cyanobacteria., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

The development of industry has resulted in excessive environmental zinc exposure which has caused various health problems in a wide range of organisms including humans. The mechanisms by which aquatic microorganisms respond to environmental zinc stress are still poorly understood. Paramecium, a well-known ciliated protozoan and a popular cell model in heavy metal stress response studies, was chosen as the test unicellular eukaryotic organism in the present research. In this work, Paramecium cf. multimicronucleatum cells were exposed in different levels of zinc ion (0.1 and 1.0 mg/L) for different periods of exposure (1 and 4 days), and then analyzed population growth, transcriptomic profiles and physiological changes in antioxidant enzymes to explore the toxicity and detoxification mechanisms during the zinc stress response. Results demonstrated that long-term zinc exposure could have restrained population growth in ciliates, however, the response mechanism to zinc exposure in ciliates is likely to show a dosage-dependent and time-dependent manner. The differentially expressed genes (DEGs) were identified the characters by high-throughput sequencing, which remarkably enriched in the phagosome, indicating that the phagosome pathway might mediate the uptake of zinc, while the pathways of ABC transporters and Na + /K + -transporting ATPase contributed to the efflux transport of excessive zinc ions and the maintenance of osmotic balance, respectively. The accumulation of zinc ions triggered a series of adverse effects, including damage to DNA and proteins, disturbance of mitochondrial function, and oxidative stress. In addition, we found that gene expression changed significantly for metal ion binding, energy metabolism, and oxidation-reduction processes. RT-qPCR of ten genes involved in important biological functions further validated the results of the transcriptome analysis. We also continuously monitored changes in activity of four antioxidant enzymes (SOD, CAT, POD and GSH-PX), all of which peaked on day 4 in cells subjected to zinc stress. Collectively, our results indicate that excessive environmental zinc exposure initially causes damage to cellular structure and function and then initiates detoxification mechanisms to maintain homeostasis in P. cf. multimicronucleatum cells., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Bisphenol A (BPA) is a widely used plasticizer agent and a well-known ubiquitous endocrine disruptor, which is frequently associated with a series of reproductive, developmental, and transgenerational effects over wildlife, livestocks, and humans. Although extensive toxicological data is available for metazoans, the impact of BPA over unicellular eukaryotes, which represents a considerable proportion of eukaryotic diversity, remains largely overlooked. Here, we used acute end-point toxicological assay and an inverted virtual-screening (IVS) approach to evaluate cellular impairments infringed by BPA over the cosmopolitan ciliated protist, Paramecium caudatum. Our data indicate a clear time-dependent effect over P. caudatum survival, which seems to be a consequence of disruptions to multiple core cellular functions, such as DNA and cell replication, transcription, translation and signaling pathways. Finally, the use of this ciliate as a biosensor to monitor BPA within environments and the relevance of bioinformatic methods to leverage our current knowledge on the impacts of emerging contaminants to biological systems are discussed., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier GmbH. All rights reserved.)

Although predation risk exists under natural conditions, its role is usually ignored when evaluating the ecotoxicity of environmental contaminants, and the interaction between predation risk and antibiotic ecotoxicity is not yet clear. To investigate the nonconsumptive effects (NCEs) of predation on the ecotoxicity evaluation of antibiotics, the median lethal concentration (LC 50 ), relative population growth rate (RGR), and activities of three antioxidases were measured in the ciliate Paramecium jenningsi exposed to graded concentrations of the antibiotics nitrofurazone (NFZ) or erythromycin (ERY) in the presence or absence of a predator, i.e., the ciliate Didinium nasutum. The results showed that (1) NCEs significantly reduced the LC 50 of NFZ but had no effect on that of ERY; (2) predation pressure alone had no significant effect on the inhibitory rate of the P. jenningsi population, but the interaction with NFZ was synergistic, while that with CRY was additive; (3) the concentrationresponse (i.e., mortality) model for each antibiotic exposure with and without predation pressure differed significantly in the parameter slope; (4) RGRs were significantly reduced by antibiotic exposure or NCEs; only in NFZ-exposed groups did the RGRs decrease linearly with increasing exposure concentration; and (5) the activities of all three antioxidases significantly increased due to NCEs or following exposure to antibiotics. In brief, NCEs were detected in P. jenningsi, and these had additive or synergistic effects on antibiotic ecotoxicity, but their magnitude depended on the properties and exposure concentrations of the antibiotics. Our findings suggest that it is necessary to consider the roles of NCEs in the ecotoxicity evaluation of environmental contaminants., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Ever since the pioneering studies in the 1960s and 70s, the importance of order transitions for cell membrane functions has remained a matter of debate. Recently, it has been proposed that the nonlinear stimulus-response curve of excitable cells, which manifests in all-or-none pulses (action potentials (AP)), is due to a transition in the cell membrane. Indeed, evidence for transitions has accumulated in plant cells and neurons, but studies with other excitable cells are expedient in order to show if this finding is of a general nature. Herein, we investigated intact, motile specimens of the "swimming neuron" Paramecium. The cellular membranes were labelled with the solvatochromic fluorophores LAURDAN or Di-4-ANEPPDHQ. Subsequently, a cell was trapped in a microfluidic channel and investigated by fluorescence spectroscopy. The generalized polarization (GP) of the fluorescence emission from cell cortical membranes (probably plasma and alveolar membranes) was extracted by an edge-finding algorithm. The thermo-optical state diagram, i.e. the dependence of GP on temperature, exhibited clear indications for a reversible transition. This transition had a width of ~10-15 °C and a midpoint that was located ~4 °C below the growth temperature. The state diagrams with LAURDAN and Di-4-ANEPPDHQ had widely identical characteristics. These results suggested that the cortical membranes of Paramecium reside in an order transition regime under physiological growth conditions. Based on these findings, membrane potential fluctuations, spontaneous depolarizing spikes, and thermal excitation of Paramecium was interpreted., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

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., (© 2022. The Author(s).)

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]

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]

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)., (Copyright © 2018 Elsevier Inc. All rights reserved.)

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]

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., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

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]

In the past 10 years, the number of endosymbionts described within the bacterial order Rickettsiales has constantly grown. Since 2006, 18 novel Rickettsiales genera inhabiting protists, such as ciliates and amoebae, have been described. In this work, we characterize two novel bacterial endosymbionts from Paramecium collected near Bloomington, IN. Both endosymbiotic species inhabit the cytoplasm of the same host. The Gram-negative bacterium "Candidatus Bealeia paramacronuclearis" occurs in clumps and is frequently associated with the host macronucleus. With its electron-dense cytoplasm and a distinct halo surrounding the cell, it is easily distinguishable from the second smaller symbiont, "Candidatus Fokinia cryptica," whose cytoplasm is electron lucid, lacks a halo, and is always surrounded by a symbiontophorous vacuole. For molecular characterization, the small-subunit rRNA genes were sequenced and used for taxonomic assignment as well as the design of species-specific oligonucleotide probes. Phylogenetic analyses revealed that "Candidatus Bealeia paramacronuclearis" clusters with the so-called "basal" Rickettsiales, and "Candidatus Fokinia cryptica" belongs to "Candidatus Midichloriaceae." We obtained tree topologies showing a separation of Rickettsiales into at least two groups: one represented by the families Rickettsiaceae, Anaplasmataceae, and "Candidatus Midichloriaceae" (RAM clade), and the other represented by "basal Rickettsiales," including "Candidatus Bealeia paramacronuclearis." Therefore, and in accordance with recent publications, we propose to limit the order Rickettsiales to the RAM clade and to raise "basal Rickettsiales" to an independent order, Holosporales ord. nov., inside Alphaproteobacteria, which presently includes four family-level clades. Additionally, we define the family "Candidatus Hepatincolaceae" and redefine the family Holosporaceae IMPORTANCE: In this paper, we provide the characterization of two novel bacterial symbionts inhabiting the same Paramecium host (Ciliophora, Alveolata). Both symbionts belong to "traditional" Rickettsiales, one representing a new species of the genus "Candidatus Fokinia" ("Candidatus Midichloriaceae"), and the other representing a new genus of a "basal" Rickettsiales According to newly characterized sequences and to a critical revision of recent literature, we propose a taxonomic reorganization of "traditional" Rickettsiales that we split into two orders: Rickettsiales sensu stricto and Holosporales ord. nov. This work represents a critical revision, including new records of a group of symbionts frequently occurring in protists and whose biodiversity is still largely underestimated., (Copyright © 2016 Szokoli et al.)

Endosymbioses are driving forces underlying cell evolution. The endosymbiosis exhibited by Paramecium bursaria is an excellent model with which to study symbiosis. A single-cell microscopic analysis of P. bursaria reveals that endosymbiont numbers double when the host is in the division phase. Consequently, endosymbionts must arrange their cell cycle schedule if the culture-condition-dependent change delays the generation time of P. bursaria. However, it remains poorly understood whether endosymbionts keep pace with the culture-condition-dependent behaviors of P. bursaria, or not. Using microscopy and flow cytometry, this study investigated the life cycle behaviors occurring between endosymbionts and the host. To establish a connection between the host cell cycle and endosymbionts comprehensively, multivariate analysis was applied. The multivariate analysis revealed important information related to regulation between the host and endosymbionts. Results show that dividing endosymbionts underwent transition smoothly from the division phase to interphase, when the host was in the logarithmic phase. In contrast, endosymbiont division stagnated when the host was in the stationary phase. This paper explains that endosymbionts fine-tune their cell cycle pace with their host and that a synchronous life cycle between the endosymbionts and the host is guaranteed in the symbiosis of P. bursaria.

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]

Paramecium is a single cell able to divide in its morphologically differentiated stage that has many cilia anchored at its cell surface. Many thousands of cilia are thus assembled in a short period of time during division to duplicate the cell pattern while the cell continues swimming. Most, but not all, of these sensory cilia are motile and involved in two main functions: prey capture and cell locomotion. These cilia display heterogeneity, both in their length and their biochemical properties. Thanks to these properties, as well as to the availability of many postgenomic tools and the possibility to follow the regrowth of cilia after deciliation, Paramecium offers a nice opportunity to study the assembly of the cilia, as well as the genesis of their diversity within a single cell. In this paper, after a brief survey of Paramecium morphology and cilia properties, we describe the tools and the protocols currently used for immunofluorescence, transmission electron microscopy, and ultrastructural immunocytochemistry to analyze cilia, with special recommendations to overcome the problem raised by cilium diversity., (Copyright © 2015. Published by Elsevier Inc.)

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]

Paramecium species are extremely valuable organisms to enable experiments for the reestablishment of endosymbiosis. This is investigated in two different systems, the first with Paramecium caudatum and the endonuclear symbiotic bacterium Holospora species. Although most endosymbiotic bacteria cannot grow outside the host cell as a result of their reduced genome size, Holospora species can maintain their infectivity for a limited time. We found that an 89-kDa periplasmic protein has an important function for Holospora's invasion into the target nucleus, and that Holospora alters the host gene expression; the host thereby acquires resistance against various stresses. The second system is the symbiosis between P. bursaria and symbiotic Chlorella. Alga-free P. bursaria and the algae retain the ability to grow without a partner. Consequently, endosymbiosis between the aposymbiotic host cells and the symbiotic algae can be reestablished easily by mixing them. We now found four checkpoints for the reestablishment of the endosymbiosis between P. bursaria and the algae. The findings in the two systems provide excellent opportunities for us to elucidate not only infection processes but also to assess the associations leading to eukaryotic cell evolution. This paper summarizes recent progresses on reestablishment of the primary and the secondary endosymbiosis in Paramecium., (Copyright © 2011 Elsevier GmbH. All rights reserved.)

Paramecium calkinsi (Ciliophora, Protozoa) is a euryhaline species which was first identified in freshwater habitats, but subsequently several strains were also collected from brackish water. It is characterized by clockwise spiral swimming movement and the general morphology of the "bursaria type." The present paper is the first molecular characterization of P. calkinsi strains recently collected in distant regions in Russia using ITS1-5.8S- ITS2-5'LSU rDNA (1100bp) and COI (620bp) mtDNA sequenced gene fragments. For comparison, our molecular analysis includes P. bursaria, exhibiting a similar "bursaria morphotype" as well as species representing the "aurelia type," i.e., P. caudatum, P. multimicronucleatum, P. jenningsi, and P. schewiakoffi, and some species of the P. aurelia species complex (P. primaurelia, P. tetraurelia, P. sexaurelia, and P. tredecaurelia). We also use data from GenBank concerning other species in the genus Paramecium and Tetrahymena (which used as an outgroup). The division of the genus Paramecium into four subgenera (proposed by Fokin et al. 2004) is clearly presented by the trees. There is a clear separation between P. calkinsi strains collected from different regions (races). Consequently, given the molecular distances between them, it seems that these races may represent different syngens within the species., (Copyright © 2011 Elsevier GmbH. All rights reserved.)

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]