Andrea Valigurová | Masaryk University (original) (raw)

Papers by Andrea Valigurová

Microorganisms

Parasitic protists cause some of the most well-known human and animal diseases such as malaria, t... more Parasitic protists cause some of the most well-known human and animal diseases such as malaria, toxoplasmosis, amoebic meningitis, sleeping sickness, leishmaniosis, and diarrheal illness of protozoan origin (e [...]

The diagrams of E. duboscqi, gregarines and crypto... more The diagrams of E. duboscqi, gregarines and cryptosporidia are based on our personal observations enriched by published data. The diagram of eimeriids represents our interpretation and summary of published micrographs, where only maturing or mature stages were clearly shown [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125063#pone.0125063.ref036" target="_blank">36</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125063#pone.0125063.ref038" target="_blank">38</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125063#pone.0125063.ref040" target="_blank">40</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125063#pone.0125063.ref042" target="_blank">42</a>– <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125063#pone.0125063.ref044" target="_blank">44</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125063#pone.0125063.ref064" target="_blank">64</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125063#pone.0125063.ref065" target="_blank">65</a>]. In this scheme, we refer to the host-derived envelope (described as a parasitophorous vacuole throughout literature) of eimeriids in epicellular location as a parasitophorous sac (PS) due to its organisation similar to that in cryptosporidia and E. duboscqi. Three colours are used to distinguish between the parasite (in purple), the host cell including its parts modified due to parasitisation (in pink) and the contact zone between the host and the parasite (in yellow) where the interrelationships of the two organisms become more intimate. In the case of host-parasite cellular interactions in E. duboscqi and epicellular eimeriids, the internal space between the parasite and PS remained colourless, even though we do not exclude the possibility that this region may serve as a transitional zone for intensive interactions between the host and its parasite. A-D. Eleutheroschizon duboscqi. A. Attached zoite transforming into a trophozoite stage, already completely enveloped by a PS. B. Maturing trophozoite with a forming ring of fascicles at the attachment site. The tail forms at the caudal part of the PS. C. Mature trophozoite with a prominent tail. Note the presence of attachment fascicles and lobes. D. Detailed view of the annular joint point (the cut-out is marked by a red square in C). E-H. Eugregarines. E. Sporozoite immediately after attachment to the host epithelial cell. F. Transformation of the sporozoite into a trophozoite stage. G. Early trophozoite with a well-developed epimerite. H. Detailed view of the membrane fusion site (the cut-out is marked by red square in G). The two cytomembranes end at the point of membrane fusion, where the osmiophilic ring is formed. I-L. Cryptosporidia. I. Attached zoite transforming into a trophozoite stage, partially enveloped by an incomplete PS. J. Young trophozoite almost completely enveloped by a PS. Note the tunnel connection between the interior of the anterior vacuole and the host cell cytoplasm that developed as the result of the Y-shaped membrane junction. K. Mature stage with a prominent filamentous projection at the base of the PS and with a fully developed feeder organelle, the lamellae of which formed from the anterior vacuole membrane. L. Detailed view of the Y-shaped membrane junction (the cut-out is marked by a red square in K). M-P. Epicellular eimeriids. M. Invading zoite. N. Trophozoite/meront stage enveloped by a PS with a single attachment area (monopodial form). O. Extension of the gamont stage above the microvillous region leading to an establishment of a new contact with the host cell apart from the primary attachment zone by penetration of the PS membrane to the base of fused microvilli (spider-like form). P. Detailed view of the attachment area (the cut-out is marked by a red square in O). av—anterior vacuole, b—epimeritic bud, cm—parasite cytomembranes, cv—epimeritic cortical vesicle, db—dense band (in cryptosporidia usually consisting of several layers), f—membrane fusion site, dl—dense line separating the feeder organelle from the filamentous projection of the PS, fa—attachment fascicle of filaments, fo—feeder organelle with membranous lamellae, fom—membrane limiting the lamellae of feeder organelle, fp—filamentous projection of the PS, fs—flask-shaped structure, hc—host cell, hm—host cell plasma membrane, if—incomplete fusion of PS, int—interface between the host cell and eugregarine epimerite, consisting of host cell plasma membrane, epimerite plasma membrane and a dense layer in between, ipm—inner membrane of the PS, is—internal space…

Additional file 1. Tegument organisation in diporpa and juvenile stage of Eudiplozoon nipponicum.... more Additional file 1. Tegument organisation in diporpa and juvenile stage of Eudiplozoon nipponicum. A. General view of a diporpa tegument. TEM. B. General view of a juvenile tegument. TEM. apm – apical plasma membrane, bl – basal lamina, bpm – basal plasma membrane, m – body wall musculature, n – nucleus, p – parenchyma, sc – syncytium.

This study focused on the attachment strategy, cell structure and the host-parasite interac-tions... more This study focused on the attachment strategy, cell structure and the host-parasite interac-tions of the protococcidian Eleutheroschizon duboscqi, parasitising the polychaete Scolo-plos armiger. The attached trophozoites and gamonts of E. duboscqi were detected at different development stages. The parasite develops epicellularly, covered by a host cell-derived, two-membrane parasitophorous sac forming a caudal tipped appendage. Staining with Evans blue suggests that this tail is protein-rich, supported by the presence of a fibrous substance in this area. Despite the ultrastructural evidence for long filaments in the tail, it stained only weakly for F-actin, while spectrin seemed to accumulate in this area. The at-tachment apparatus consists of lobes arranged in one (trophozoites) or two (gamonts) cir-cles, crowned by a ring of filamentous fascicles. During trophozoite maturation, the internal space between the parasitophorous sac and parasite turns translucent, the parasite trilami-...

Microorganisms, 2021

Apicomplexa are unicellular eukaryotes that parasitise a wide spectrum of invertebrates and verte... more Apicomplexa are unicellular eukaryotes that parasitise a wide spectrum of invertebrates and vertebrates, including humans. In their hosts, they occupy a variety of niches, from extracellular cavities (intestine, coelom) to epicellular and intracellular locations, depending on the species and/or developmental stages. During their evolution, Apicomplexa thus developed an exceptionally wide range of unique features to reach these diversified parasitic niches and to survive there, at least long enough to ensure their own transmission or that of their progeny. This review summarises the current state of knowledge on the attachment/invasive and nutrient uptake strategies displayed by apicomplexan parasites, focusing on trophozoite stages of their so far poorly studied basal representatives, which mostly parasitise invertebrate hosts. We describe their most important morphofunctional features, and where applicable, discuss existing major similarities and/or differences in the corresponding...

Microorganisms, 2021

After invading the host organism, a battle occurs between the parasitic protists and the host’s i... more After invading the host organism, a battle occurs between the parasitic protists and the host’s immune system, the result of which determines not only whether and how well the host survives and recovers, but also the fate of the parasite itself. The exact weaponry of this battle depends, among others, on the parasite localisation. While some parasitic protists do not invade the host cell at all (extracellular parasites), others have developed successful intracellular lifestyles (intracellular parasites) or attack only the surface of the host cell (epicellular parasites). Epicellular and intracellular protist parasites have developed various mechanisms to hijack host cell functions to escape cellular defences and immune responses, and, finally, to gain access to host nutrients. They use various evasion tactics to secure the tight contact with the host cell and the direct nutrient supply. This review focuses on the adaptations and evasion strategies of parasitic protists on the exampl...

Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37, Br... more Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37, Brno, Czech Republic Department of Invertebrate Zoology, Faculty of Biology, St. Petersburg State University, Universitetskaya emb. 7/9, Saint-Petersburg, 199 034, Russian Federation Department of Invertebrate Zoology, Faculty of Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119 234, Russian Federation Belozersky Institute for Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119 234, Russian Federation

Background: Monogeneans, in general, show a range of unique adaptations to a parasitic lifestyle,... more Background: Monogeneans, in general, show a range of unique adaptations to a parasitic lifestyle, making this group enormously diverse. Due to their unique biological properties, diplozoid monogeneans represent an attractive model group for various investigations on diverse biological interactions. However, despite numerous studies, there are still gaps in our knowledge of diplozoid biology and morphofunctional adaptation.Results: In this study, we provide a complex microscopic analysis of systems/structures involved in niche searching, sensing and self-protection against the host environment, and excretory/secretory processes in Eudiplozoon nipponicum. Freeze-etching enabled us to detect syncytium organisational features not visible by TEM alone, such as the presence of a membrane subjacent to the apical plasma membrane (separated by a dense protein layer) and a lack of basal plasma membrane. We located several types of secretory/excretory vesicles and bodies, including those attac...

Parasitology Research, 2019

Representatives of Apicomplexa perform various kinds of movements that are linked to the differen... more Representatives of Apicomplexa perform various kinds of movements that are linked to the different stages of their life cycle. Ancestral apicomplexan lineages, including gregarines, represent organisms suitable for research into the evolution and diversification of motility within the group. The vermiform trophozoites and gamonts of the archigregarine Selenidium pygospionis perform a very active type of bending motility. Experimental assays and subsequent light, electron, and confocal microscopic analyses demonstrated the fundamental role of the cytoskeletal proteins actin and tubulin in S. pygospionis motility and allowed us to compare the mechanism of its movement to the gliding machinery (the so-called glideosome concept) described in apicomplexan zoites. Actin-modifying drugs caused a reduction in the movement speed (cytochalasin D) or stopped the motility of archigregarines completely (jasplakinolide). Microtubule-disrupting drugs (oryzalin and colchicine) had an even more noticeable effect on archigregarine motility. The fading and disappearance of microtubules were documented in ultrathin sections, along with the formation of α-tubulin clusters visible after the immunofluorescent labelling of drug-treated archigregarines. The obtained data indicate that subpellicular microtubules most likely constitute the main motor structure involved in S. pygospionis bending motility, while actin has rather a supportive function.

PLOS ONE, 2018

Diplozoidae (Monogenea) are blood-feeding freshwater fish gill ectoparasites with extraordinary b... more Diplozoidae (Monogenea) are blood-feeding freshwater fish gill ectoparasites with extraordinary body architecture and a unique sexual behaviour in which two larval worms fuse and transform into one functioning individual. In this study, we describe the body organisation of Paradiplozoon homoion adult stage using a combined approach of confocal laser scanning and electron microscopy, with emphasis on the forebody and hindbody. Special attention is given to structures involved in functional adaptation to ectoparasitism, i.e. host searching, attachment and feeding/metabolism. Our observations indicate clear adaptations for blood sucking, with a well-innervated mouth opening surrounded by sensory structures, prominent muscular buccal suckers and a pharynx. The buccal cavity surface is covered with numerous tegumentary digitations that increase the area in contact with host tissue and, subsequently, with its blood. The buccal suckers and the well-innervated haptor (with sclerotised clamps controlled by noticeable musculature) cooperate in attaching to and moving over the host. Putative gland cells accumulate in the region of apical circular structures, pharynx area and in the haptor middle region. Paired club-shaped sacs lying laterally to the pharynx might serve as secretory reservoirs. Furthermore, we were able to visualise the body wall musculature, including peripheral innervation, the distribution of uniciliated sensory structures essential for reception of external environmental information, and flame cells involved in excretion. Our results confirm in detail that P. homoion displays a range of sophisticated adaptations to an ectoparasitic life style, characteristic for diplozoid monogeneans.

Scientific Reports, 2019

Acanthamoebae success as human pathogens is largely due to the highly resistant cysts which repre... more Acanthamoebae success as human pathogens is largely due to the highly resistant cysts which represent a crucial problem in treatment of Acanthamoeba infections. Hence, the study of cyst wall composition and encystment play an important role in finding new therapeutic strategies. For the first time, we detected high activity of cytoskeletal elements-microtubular networks and filamentous actin, in late phases of encystment. Cellulose fibrils-the main components of endocyst were demonstrated in inter-cystic space, and finally in the ectocyst, hereby proving the presence of cellulose in both layers of the cyst wall. We detected clustering of intramembranous particles (IMPs) and their density alterations in cytoplasmic membrane during encystment. We propose a hypothesis that in the phase of endocyst formation, the IMP clusters represent cellulose microfibril terminal complexes involved in cellulose synthesis that after cyst wall completion are reduced. Cyst wall impermeability, due largely to a complex polysaccharide (glycans, mainly cellulose) has been shown to be responsible for Acanthamoeba biocide resistance and cellulose biosynthesis pathway is suggested to be a potential target in treatment of Acanthamoeba infections. Disruption of this pathway would affect the synthesis of cyst wall and reduce considerably the resistance to chemotherapeutic agents. Species of free-living amoebae genus Acanthamoeba Volkonsky, 1931 are opportunistic unicellular parasites with worldwide distribution in diverse environments including freshwater, soil, man-made habitats and even clinical settings 1-4. Pathogenic strains are causative agents of usually fatal chronic granulomatous amoebic encephalitis (GAE) and disseminating diseases in immunodeficient individuals and Acanthamoeba keratitis (AK), a painful progressive eye disease in immunocompetent individuals. The constantly rising number of cases of amoebic keratitis is connected with the increasing use of contact lenses and improving awareness 5. To date, not any standard and reliable therapeutic procedures of Acanthamoeba infections have been developed. The treatment of GAE and disseminated infections is limited and only rarely successful 6,7. AK is treated with a series of drugs with various and inconsistent effects, easily manageable treatment is still not available 8,9. The life cycle of Acanthamoeba spp. comprises two stages: an active trophozoite and a dormant, metabolically almost inactive cyst. Trophozoite is a motile stage typical with hyaline spiny subpseudopodia-acanthopodia, produced on the leading pseudopodium and on the entire cell surface 10,11. In unfavourable environmental conditions or in tissues during persistent infections trophozoites encyst 12-14. Cyst stage is typical with a conspicuous double-layered cyst wall, consisting of ectocyst, composed mostly of proteins and polysaccharides, and endocyst, composed mostly of cellulose 15,16. Except for cyst pores (ostioles), these layers are separated by an inter-cystic

Protist, 2018

Selenidium spp. n.: Structure and Phylogeny 827 (concatenated SSU, 5.8S, LSU rDNAs) sequences inc... more Selenidium spp. n.: Structure and Phylogeny 827 (concatenated SSU, 5.8S, LSU rDNAs) sequences including S. pygospionis sequences. Although being preliminary, they nevertheless revealed the monophyly of gregarines previously challenged by many molecular phylogenetic studies. Despite their molecular-phylogenetic heterogeneity, archigregarines exhibit an extremely conservative plesiomorphic structure; their ultrastructural key features appear to be symplesiomorphies rather than synapomorphies.

Protist, 2018

Blastogregarines are poorly studied parasites of polychaetes superficially resembling gregarines,... more Blastogregarines are poorly studied parasites of polychaetes superficially resembling gregarines, but lacking syzygy and gametocyst stages in the life cycle. Furthermore, their permanent multinuclearity and gametogenesis by means of budding considerably distinguish them from other parasitic Apicomplexa such as coccidians and hematozoans. The affiliation of blastogregarines has been uncertain: different authors considered them highly modified gregarines, an intermediate apicomplexan lineage between gregarines and coccidians, or an isolated group of eukaryotes altogether. Here, we report the ultrastructure of two blastogregarine species, Siedleckia nematoides and Chattonaria mesnili, and provide the first molecular data on their phylogeny based on SSU, 5.8S, and LSU rDNA sequences. Morphological analysis reveals that blastogregarines possess both gregarine and coccidian features. Several traits shared with archigregarines likely represent the ancestral states of the corresponding cell...

PLOS ONE, 2017

Recent studies on motility of Apicomplexa concur with the so-called glideosome concept applied fo... more Recent studies on motility of Apicomplexa concur with the so-called glideosome concept applied for apicomplexan zoites, describing a unique mechanism of substrate-dependent gliding motility facilitated by a conserved form of actomyosin motor and subpellicular microtubules. In contrast, the gregarines and blastogregarines exhibit different modes and mechanisms of motility, correlating with diverse modifications of their cortex. This study focuses on the motility and cytoskeleton of the blastogregarine Siedleckia nematoides Caullery et Mesnil, 1898 parasitising the polychaete Scoloplos cf. armiger (Mü ller, 1776). The blastogregarine moves independently on a solid substrate without any signs of gliding motility; the motility in a liquid environment (in both the attached and detached forms) rather resembles a sequence of pendular, twisting, undulation, and sometimes spasmodic movements. Despite the presence of key glideosome components such as pellicle consisting of the plasma membrane and the inner membrane complex, actin, myosin, subpellicular microtubules, micronemes and glycocalyx layer, the motility mechanism of S. nematoides differs from the glideosome machinery. Nevertheless, experimental assays using cytoskeletal probes proved that the polymerised forms of actin and tubulin play an essential role in the S. nematoides movement. Similar to Selenidium archigregarines, the subpellicular microtubules organised in several layers seem to be the leading motor structures in blastogregarine motility. The majority of the detected actin was stabilised in a polymerised form and appeared to be located beneath the inner membrane complex. The experimental data suggest the subpellicular microtubules to be associated with filamentous structures (= cross-linking protein complexes), presumably of actin nature.

European Journal of Protistology, 2017

Gregarines represent a highly diversified group of ancestral apicomplexans, with various modes of... more Gregarines represent a highly diversified group of ancestral apicomplexans, with various modes of locomotion and hostparasite interactions. The eugregarine parasite of the barnacle Balanus balanus, Cephaloidophora cf. communis, exhibits interesting organisation of its attachment apparatus along with unique motility modes. The pellicle covered gregarine is arranged into longitudinal epicytic folds. The epimerite is separated from the protomerite by a septum consisting of tubulin-rich filamentous structures and both are packed with microneme-like structures suggestive of their function in the production of adhesives important for attachment and secreted through the abundant epimerite pores. Detached trophozoites and gamonts are capable of gliding motility, enriched by jumping and rotational movements with rapid changes in gliding direction and cell flexions. Actin in its polymerised form (F-actin) is distributed throughout the entire gregarine, while myosin, detected in the cortical region of the cell, follows the pattern of the epicytic folds. Various motility modes exhibited by individuals of C. cf. communis, together with significant changes in their cell shape during locomotion, are not concordant with the gliding mechanisms generally described in apicomplexan zoites and indicate that additional structures must be involved (e.g. two 12-nm filaments; the specific dentate appearance of internal lamina inside the epicytic folds).

The Journal of eukaryotic microbiology, 2017

A novel species of aseptate eugregarine, Ganymedes yurii sp. n., is described using microscopic a... more A novel species of aseptate eugregarine, Ganymedes yurii sp. n., is described using microscopic and molecular approaches. It inhabits the intestine of Gondogeneia sp., a benthic amphipod found along the shore of James Ross Island, Weddell Sea, Antarctica. The prevalence of the infection was very low and only a few caudo-frontal syzygies were found. Morphologically, the new species is close to a previously described amphipod gregarine, Ganymedes themistos, albeit with several dissimilarities in the structure of the contact zone between syzygy partners, as well as other characteristics. Phylogenetic analysis of the 18S rDNA from G. yurii supported a close relationship between these species. These two species were grouped with other gregarines isolated from crustaceans hosts (Cephaloidophoroidea); however, statistical support throughout the clade of Cephaloidophoroidea gregarines was minimal using the available dataset.

Protist, 2016

Archigregarines, an early branching lineage within Apicomplexa, are a poorly-known group of inver... more Archigregarines, an early branching lineage within Apicomplexa, are a poorly-known group of invertebrate parasites. By their phylogenetic position, archigregarines are an important lineage to understand the functional transition that occurred between freeliving flagellated predators to obligatory parasites in Apicomplexa. In this study, we provide new ultrastructural data and phylogenies based on SSU rDNA sequences using the type species of archigregarines, the Selenidiidae Selenidium pendula Giard, 1884. We describe for the first time the syzygy and early gamogony at the ultrastructural level, revealing a characteristic nuclear multiplication with centrocones, cryptomitosis, filamentous network of chromatin, a cyst wall secretion and a 9+0 flagellar axoneme of the male gamete. S. pendula belongs to a monophyletic lineage that includes several other related species, all infecting Sedentaria Polychaeta (Spionidae, Sabellaridae, Sabellidae and Cirratulidae). All of these Selenidium species exhibit similar biological characters: a cell cortex with the plasma membrane-inner membrane complex-subpellicular microtubule sets, an apical complex with the conoid, numerous rhoptries and micronemes, a myzocytosis with large food vacuoles, a nuclear multiplication during syzygy and young gamonts. Two other distantly related Selenidium-like lineages infect Terebellidae and Sipunculida, underlying the ability of archigregarines to parasite a wide range of marine hosts.

Protist, Jun 17, 2016

Urosporids (Apicomplexa: Urosporidae) are eugregarines that parasitise marine invertebrates, such... more Urosporids (Apicomplexa: Urosporidae) are eugregarines that parasitise marine invertebrates, such as annelids, molluscs, nemerteans and echinoderms, inhabiting their coelom and intestine. Urosporids exhibit considerable morphological plasticity, which correlates with their different modes of motility and variations in structure of their cortical zone, according to the localisation within the host. The gregarines Urospora ovalis and U. travisiae from the marine polychaete Travisia forbesii were investigated with an emphasis on their general morphology and phylogenetic position. Solitary ovoid trophozoites and syzygies of U. ovalis were located free in the host coelom and showed metabolic activity, a non-progressive movement with periodic changes of the cell shape. Solitary trophozoites of U. travisiae, attached to the host tissue or free floating in the coelom, were V-shaped. Detached trophozoites demonstrated gliding motility, a progressive movement without observable cell body chan...

Environmental Microbiology Reports, 2016

Parasitology Research, 2015

This study aimed to evaluate and document the excystation process of Cryptosporidium muris oocyst... more This study aimed to evaluate and document the excystation process of Cryptosporidium muris oocysts in various incubation media, and to monitor the behaviour of excysting and freshly excysted sporozoites. A test of oocyst viability, using fluorescent double staining with fluorescein diacetate and propidium iodide, was performed prior to each experimental assay. Light microscope observations confirmed that relatively often only three sporozoites were released; the fourth one either left the oocyst later together with a residual body or remained trapped within the oocyst wall. These results suggest that successful oocyst excystation is not limited by the viability of all four sporozoites. Darkening of oocysts to opaque and their specific movement (the so-called &amp;quot;oocyst dancing&amp;quot;) preceded the final excystation and liberation of sporozoites, while the dormant oocysts appeared refractive. The process of excystation in C. muris is not gradual as generally described in cryptosporidia but very rapid in an eruptive manner. Experiments were performed using oocysts stored at 4 °C for various time periods, as well as oocysts freshly shed from host rodents (Mastomys coucha) of different ages. The most suitable medium supporting high excystation rate (76 %) and prolonged motility of sporozoites was RPMI 1640, enriched with 5 % bovine serum albumin (BSA). Our results emphasize that to reliably evaluate the success of in vitro excystation of cryptosporidia, not only the number of released sporozoites in a set time period should be taken into consideration but also their subsequent activity (motility), as it is expected to be essential for the invasion of host cells.

Microorganisms

Microorganisms, 2021

Parasitology Research, 2019

PLOS ONE, 2018

Scientific Reports, 2019

Protist, 2018

PLOS ONE, 2017

European Journal of Protistology, 2017

The Journal of eukaryotic microbiology, 2017

Protist, 2016

Protist, Jun 17, 2016

Environmental Microbiology Reports, 2016

Parasitology Research, 2015