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PubMedDate not supplied

[Parasitic amoebae and amoebo-flagellates from the Lobosea and heterolobosea classes].

Different cited evidences on parasitic amoebae and amoebo-flagellates belonging to the Lobosea and Heterolobosea classes (Pages, 1987) have been reviewed. Special attention is paid to various degree of their adaptation to parasitic mode of life, which ranges from a parasitism on a border with commensalism to true parasitism (both facultative and obligatory ones). Besides the coprophilous and commensal species, the number of true parasites among the Lobosea and Heterolobosea classes is comparatively small. In many cases, both facultative and obligatory parasites cause the death of their hosts. Apparently this strongly pronounced pathogenicity of parasitic amoebae and amoebo-flagellates suggest a recent origin of such parasite-host systems. Pathogens of amoebic dysentry, primary amoebic meningoencephalitis and granulomatous amoebic encephalitis are specially considered. In the Russian text-books on a parasitology the information on most of them, except Entamoeba hystolytica, is either totally absent or very scare and out of date.

Amoeba↗

PubMed2002

Morphological, ecological and molecular studies of Vannella simplex Wohlfarth-Bottermann 1960 (Lobosea, Gymnamoebia), with a new diagnosis of this species.

Vannella simplex (Gymnamoebia, Vannellidae) is one of the most common amoebae species, recorded from a variety of regions. It was originally described as a freshwater species, but has also been reported from shallow-water regions of the Baltic Sea. In the present work, we investigated the morphology and biology of three V. simplex isolates, originating from geographically distant regions. Among them is one brackish water strain, isolated from artificial cyanobacterial mats, which were originally sampled in Nivå Bay (Baltic Sea, The Sound). The strain is cyst-forming and can thrive at salinity ranges from 0-50 ppt. Phylogenetic relationships were investigated by sequencing partial SSU rDNA of the cultured V. simplex isolates. Additional sequences were obtained from four environmental DNA extractions of sediment samples collected from different localities in Switzerland. Analysis of all obtained sequences revealed a monophyletic group. Based on the analysis and comparison of morphological, ecological and molecular data sets we compiled a distribution map of V. simplex and propose an emendation of this species.

Animals↗

PubMed2003

Spatial distribution of gymnamoebae (Rhizopoda, Lobosea) in brackish-water sediments at the scale of centimeters and millimeters.

In order to study micro-spatial distribution of amoebae, an intact slice of sandy sediment from the brackish-water Nivå Bay (Baltic Sea, The Sound), 40 x 24 mm in size and 2 mm in thickness was gently sectioned into cubes, 2 x 2 x 2 mm in size. Each cube was inoculated into enrichment media to reveal the biodiversity of amoebae. Seventeen species of amoebae were recovered. The 2-D map of amoebae species distribution in the slice, consisting of 240 2 x 2 mm cells was drawn and analyzed. Results show heterogeneous distribution of amoebae at the scale of centimeters and millimeters and confirm the idea of the presence of microhabitats, selectively occupied by amoebae species. Three types of distribution patterns were found: random, aggregated and equally spaced. Microelectrode studies indicated that amoebae distribution was not related to the dissolved oxygen content in the sediment. The studied slice of sediment contained several pronounced "hotspots" of amoebae biodiversity, where up to four species co-occur in the same area. Seven species of amoebae numbered 1-4 specimens in the studied slice (i.e. there was 0.5-2 cell ml(-1)). Analysis of the amoebae distribution map shows the high probability of undersampling rare amoebae species during faunistic studies.

Animals↗

PubMed2004

Vertical distribution of gymnamoebae (rhizopoda, lobosea) in the top layer of brackish-water sediments.

The paper reports on the distribution of amoebae in a vertical slice of sandy sediment from the brackish-water Nivå Bay (Baltic Sea, The Sound). The 24 x 20 mm slice 2 mm in thickness was gently cut from the top of sediment to a depth of 20 mm using coverslips, and further sectioned into 2 x 2 x 2 mm cubes. Each cube was inoculated into enrichment media to reveal the biodiversity of amoebae. The map of amoebae species distribution in the slice was drawn and analyzed. The results show patchy distributions of many amoebae species. Amoebae tend to form a band of maximum diversity within the depth interval 2-16 mm. Two mini-cores of sediment located close to the butt-ends of the slice were collected using cut 1 ml syringes. They were sliced and inoculated to reveal the biodiversity of amoebae at different depths. The distribution patterns of amoebae in the mini-cores were similar to the ones obtained in the slice, and show evident patchiness of some species. It seems that abundant species mostly form irregular patches 1-2 cm across, whereas many species are rare and appear in few number of specimens or in patches smaller than 2 mm.

Animals↗

PubMed2006

Feeding characteristics of an amoeba (Lobosea: Naegleria) grazing upon cyanobacteria: food selection, ingestion and digestion progress.

Bacterivory by heterotrophic nanoflagellates and ciliates has been widely studied in aquatic environments, but data on the grazing of amoebae, are still scarce. From the water samples of Dianchi Lake (Kunming, Yunnan Province, China), we isolated an amoeba, designated as Naegleria sp. strain W2, which had potent grazing effects on some kind of cyanobacteria. The food selection mechanism and the digestion process of the amoeba were investigated in batch experiments. Predation experiments showed that filamentous cyanobacteria (e.g., Anabaena, Cylindrospermum, Gloeotrichia, and Phormidium) were readily consumed, with clearance rates ranging from 0.332 to 0.513 nL amoeba(-1) h(-1). The tight threads (Oscilltoria) and aggregates (Aphanizomenon) could not be ingested; however, their sonicated fragments were observed inside food vacuoles, suggesting that their morphologies prevent them from being ingested. Live video microscopy noted that unicellular Chroococcaceae (e.g., Synechococcus, Aphanocapsa, and Microcystis) were excreted after ingestion, indicating that food selection takes place inside food vacuoles. To determine whether the tastes or the toxins prevented them from being digested, heat-killed cells were retested for predation. Digestion rates and ingestion rates of the amoebae for filamentous cyanobacteria were estimated from food vacuole content volume. Through a "cold-chase" method, we found that the food vacuole contents declined exponentially in diluted amoebae cells, and digestion rates were relatively constant, averaging about 1.5% food vacuole content min(-1) at 28 degrees Celsius. Ingestion strongly depended on the satiation status of the amoebae, starved amoebae fed at higher rates compared with satiated amoebae. Our results suggest that the food selection and food processing mechanisms of the amoeba are similar to those of interception feeding flagellates; however, filamentous cyanobacteria cannot obtain a refuge under the grazing pressure of phagotrophic amoebae, which may widen our knowledge on the grazing of protists.

Amoeba↗

PubMed2006

Detection of a serine proteinase gene in Acanthamoeba genotype T6 (Amoebozoa: Lobosea).

Cytopathic proteins are assumed to contribute to the pathogenicity of Acanthamoeba spp. due to their degrading capacity that is required for tissue invasion. In this study, a serine proteinase gene was demonstrated in a highly virulent Acanthamoeba keratitis causing strain with genotype T6. This gene was detected in both, the genomic DNA and the cDNA by PCR and subsequent sequencing. The gene fragment comprises about 500 bp and exhibits high sequence similarity to the serine proteinases of Acanthamoeba strains with genotype T4 and T12. The detection of a serine proteinase in this Acanthamoeba T6 strain is significant, because while T4 is the most common genotype among pathogenic Acanthamoeba strains and also T12 is known to be associated with disease, this is the only virulent Acanthamoeba T6 strain known to date. Obviously, this serine proteinase represents a common tool in pathogenic processes during Acanthamoeba infection.

Acanthamoeba↗

PubMed2001

SSU rRNA-based phylogenetic position of the genera Amoeba and Chaos (Lobosea, Gymnamoebia): the origin of gymnamoebae revisited.

Naked lobose amoebae (gymnamoebae) are among the most abundant group of protists present in all aquatic and terrestrial biotopes. Yet, because of lack of informative morphological characters, the origin and evolutionary history of gymnamoebae are poorly known. The first molecular studies revealed multiple origins for the amoeboid lineages and an extraordinary diversity of amoebae species. Molecular data, however, exist only for a few species of the numerous taxa belonging to this group. Here, we present the small-subunit (SSU) rDNA sequences of four species of typical large gymnamoebae: Amoeba proteus, Amoeba leningradensis, Chaos nobile, and Chaos carolinense. Sequence analysis suggests that the four species are closely related to the species of genera Saccamoeba, Leptomyxa, Rhizamoeba, Paraflabellula, Hartmannella, and Echinamoeba. All of them form a relatively well-supported clade, which corresponds to the subclass Gymnamoebia, in agreement with morphology-based taxonomy. The other gymnamoebae cluster in small groups or branch separately. Their relationships change depending on the type of analysis and the model of nucleotide substitution. All gymnamoebae branch together in Neighbor-Joining analysis with corrections for among-site rate heterogeneity and proportion of invariable sites. This clade, however, is not statistically supported by SSU rRNA gene sequences and further analysis of protein sequence data will be necessary to test the monophyly of gymnamoebae.

Amoeba↗

PubMedDate not supplied

[The cultivation of Blastocystis (Rhizopoda: Lobosea) from hens and ducks].

The method of cultivation of Blastocystis galli from hens and Blastocystis sp. from ducks was worked out. Blastocystis grow on nutrient medium at pH 7.0 to 7.2 in a wide range of temperatures from 30 to 45 C. Optimum temperatures for cultivation are 41 to 42 C. The growth of cultures was obtained on biphase egg medium. Solid phase of the medium presents coagulated contents of the hen's egg. Liquid phase can be made of Henk's solution with the addition of 30% of fresh or lyophilizinic hen serum or horse serum. Henk's solution can be replaced by medium 199 (we observed the growth of culture on medium 199 without addition of blood serum). In all variants of medium we added antibiotics on a per--1 ml of medium basis: ampicillini--4 thousand units, streptomycini--1 thousand units. After 2 to 3 passages antibiotics can be excluded from the medium. Optimum medium is that with the addition of 30% of fresh hen serum. Passages go well at the transfer of 15-20% culture after 72 to 96 hours. The size of cultural stages varied within the limits of 2.5-56.2 x 2.5-56.2 microns and 2.5-110 x 2.5-110 microns for Blastocystis sp. and B. galli, respectively, the number of nuclei in one individual varied from 1 to 64, seldom over 100.

Animals↗

PubMedDate not supplied

[A finding of Blastocystis galli (Rhizopoda, Lobosea) in domestic turkeys].

Blastocysts tentatively assigned to the species Blastocystis galli were found in the turkey Meleagris gallopavo from Tajikistan and Uzbekistan. Length and width of blastocysts from turkeys vary in a wider range (2.5--55.1 x 2.5--51.3 mkm) than length and width of blastocysts from hens. The shape of blastocysts varies from round and oval to ellipsoid and amoeboid.

Animals↗

PubMedDate not supplied

[The specificity of blastocysts (Rhizopoda: Lobosea)].

The analysis of specificity of blastocysts was based on the data on host association and on experimental data. In experiments we failed to infect the geese (Anser anser) with Blastocystis galli taken from the fowl (Gallus gallus) and also failed to infect the fowl with B. suis taken from the pigs (Sus scrofa domestica). Experimental data and field observations of blastocysts distribution among different groups of hosts point out that the same species of blastocysts can not parasitize in hosts belonging to different classes and orders. The examination of 89 fish specimens belonging to 14 species of Osteichthyes taken from the Neman delta did not discover any blastocysts.

Animals↗

PubMed1986

Study of an amoeboflagellate isolated from the nasal mucosa of man.

This paper examines the biology, morphology, and pathogenicity for mice of an amoeboflagellate isolated from human nasal mucosa. The biological and morphological relationships of this isolate with the amoebae (Lobosea) and the true slime molds (Eumycetoza) are discussed though the taxonomic affinities of the organism have not been determined.

Amoeba↗

PubMedDate not supplied

Molecular evolutionary analyses of nuclear-encoded small subunit ribosomal RNA identify an independent rhizopod lineage containing the Euglyphina and the Chlorarachniophyta.

The Rhizopoda comprise a diverse assemblage of protists which depend on lobose or filose pseudopodia for locomotion. The biochemical and morphological diversity of rhizopods has led to an uncertain taxonomy. Ribosomal RNA sequence comparisons offer a measure of evolutionary relatedness that is independent of morphology and has been used to demonstrate a polyphyletic origin of the Lobosea. We sequenced complete small subunit ribosomal RNA coding regions from the filose amoebae, Euglypha rotunda and Paulinella chromatophora (Euglyphina) to position these taxa in the eukaryote phylogeny. The neighbor-joining analyses show that E. rotunda and P. chromatophora share a monophyletic origin and are not closely related to any lobose amoebae in our analyses. Instead, the Euglyphina form a robust sister group to the Chlorarachniophyta. These results provide further evidence for the polyphyly of the Rhizopoda and support the creation of a new amoeboid lineage which includes the Euglyphina and the chlorarachniophyte algae; taxa with tubular mitochondrial cristae and filose or reticulate pseudopodia.

Animals↗

PubMed2001

[Chromosome-like bodies of dysentery ameba Entamoeba histolytica].

Intact and surface stretched amembraneous nuclei of Entamoeba histolytica (Rhizopoda, Lobosea, Entamoebidae) trophozoites were studied by light and electron microscopy. A moderately dense karyosome about 1.5 microns in diameter, localized in the central part of the interphase nucleus, contains the bulk of nuclear DNA. Within the karyosome, beaded and ribbon-like chromatin bodies surrounding a loose fibrillar core are commonly recognized. The peripheral domain of both interphase and several mitotic nuclei is filled with a heterogeneous material similar in its ultrastructure to the nucleolar substance. A wide fibrogranular domain lies between this unusual nucleolus and the karyosome. Rosette-like intranuclear inclusions 0.2-0.4 micron in diameter are often seen in both the fibrogranular and nucleolar domains. At the prophase-metaphase, nearly 50 linear chromosome-like bodies are detected as being in close association with several large beaded and ribbon-like chromatin bodies. At the anaphase-telophase, the chromatin bodies per surface-stretched daughter nucleus of live entamoebae, and in each amembraneous daughter nuclear preparation number nearly 14 and 6, respectively. Besides, in each amembraneous DAPI-stained nucleus a set of 50 or so linear chromosome-like bodies are clearly identified. We infer that the nucleus of E. histolytica contains more than 50 linear chromosomes which at different stages of the cell cycle can unite into several beaded and ribbon-like associations. These form a single moderately dense chromatin karyosome in the central part of the interphase nucleus.

Animals↗

PubMedDate not supplied

[Blastocystis galli sp. n. (Protista: Rhizopoda) from the intestines of domestic hens].

A new species, Blastocystis galli, parasitic in blind processes of large intestine was found in domestic hens. Sizes of blastocysts are 7.5-35.0 x 6.25-30.0 (18.67 x 17.05) microns. The parasite form varies from round to ellipsoid. There were found stages with 1 to 4 nuclei and stages containing 8 to 32 small daughter individuals. Outside blastocysts are covered with structured glycocalyx. Under glycocalyx there is a plasmatic membrane. Cytoplasm contains a great number of ribosomes and mitochondria with cristae resembling in their shape oval or round small sacs. Nucleus contains nucleolus. Chromatin mass is concentrated on one of the poles of the nucleus as individual bodies. Semilunar in form chromatin mass was not found. Golgi apparatus is represented by a number of plates grouped in a pile. Most part of the cell is occupied by reproductive organelles divided by cytoplasmatic membranes into compartments. On the basis of its ultrafine organization. B. galli is assigned to the kingdom Protista, type Rhizopoda, class Lobosea, subclass Gymnamoebia, order Blastocystida.

Animals↗

PubMed2006

Evaluation of prokaryotic and eukaryotic cells as food source for Balamuthia mandrillaris.

Balamuthia mandrillaris is a recently identified free-living protozoan pathogen that can cause fatal granulomatous encephalitis in humans. Recent studies have shown that B. mandrillaris consumes eukaryotic cells such as mammalian cell cultures as food source. Here, we studied B. mandrillaris interactions with various eukaryotic cells including, monkey kidney fibroblast-like cells (COS-7), human brain microvascular endothelial cells (HBMEC) and Acanthamoeba (an opportunistic protozoan pathogen) as well as prokaryotes, Escherichia coli. B. mandrillaris exhibited optimal growth on HBMEC compared with Cos-7 cells. In contrast, B. mandrillaris did not grow on bacteria but remained in the trophozoite stage. When incubated with Acanthamoeba trophozoites, B. mandrillaris produced partial Acanthamoeba damage and the remaining Acanthamoeba trophozoites underwent encystment. However, B. mandrillaris were unable to consume Acanthamoeba cysts. Next, we observed that B. mandrillaris-mediated Acanthamoeba encystment is a contact-dependent process that requires viable B. mandrillaris. In support, conditioned medium of B. mandrillaris did not stimulate Acanthamoeba encystment nor did lysates of B. mandrillaris. Overall, these studies suggest that B. mandrillaris target Acanthamoeba in the trophozoite stage; however, Acanthamoeba possess the ability to defend themselves by forming cysts, which are resistant to B. mandrillaris. Further studies will examine the mechanisms associated with food selectivity in B. mandrillaris.

Acanthamoeba↗

PubMed2002

Distribution of free-living amoebae in James River, Virginia, USA.

A comprehensive survey to document the presence of free-living amoebae was conducted along 58 km of James River, near Richmond, Virginia, USA. Sites included tidal and non-tidal freshwater areas, near 40 combined sewer outflows, three municipal wastewater treatment plant release sites, and thermal discharge from a coal-fired power plant. Amoebae were present on all collection dates, spring through autumn, and at all sites ( n=330). Five genera, Naegleria, Vannella, Acanthamoeba, Vahlkampfia, and Hartmannella were present in both the water column and sediment. The most common isolates from the water column were Naegleria and Vannella. Water conditions conducive to the presence of large quantities of fecal coliform bacteria were correlated with the prevalence of free-living amoebae. Some of the amoebae in this complex ecosystem can act as opportunistic pathogens, may play a role in diseases of aquatic organisms in this heavily urbanized river, and may present a risk to human health.

Animals↗

PubMed2004

Balamuthia mandrillaris, an opportunistic agent of granulomatous amebic encephalitis, infects the brain via the olfactory nerve pathway.

Balamuthia mandrillaris is a free-living ameba and an opportunistic agent of lethal granulomatous amebic encephalitis (GAE) in humans and other mammals. Its supposed routes of infection have been largely assumed from what is known about Acanthamoeba spp. and Naegleria fowleri, other free-living amebae and opportunistic encephalitis agents. However, formal proof for any migratory pathway, from GAE patients or from animal models, has been lacking. Here, immunodeficient mice were infected with B. mandrillaris amebae by intranasal instillation, the most likely natural portal of entry. By means of classical and immunohistology, the amebae are shown to adhere to the nasal epithelium, progress along the olfactory nerves, traverse the cribriform plate of the ethmoid bone, and finally infect the brain. A similar invasion pathway has been described for N. fowleri. The data suggest that the olfactory nerve pathway is a likely route for natural infection of the brain by B. mandrillaris amebae.

Amebiasis↗

PubMed2005

Cochliopodium gallicum n. sp. (Himatismenida), an amoeba bearing unique scales, from cyanobacterial mats in the Camargue (France).

Cochliopodium gallicum n. sp., isolated from cyanobacterial mats in the Camargue (France) is the smallest marine species of Cochliopodium to date. Its unusual tectum consists of flat plate-shaped scales with honeycomb-like centres, underlain by a layer of filamentous structures connected to each other in the basal and apical parts. The tectum is very fine and can be easily lost under inappropriate EM fixation. In its light-microscopical features, this species resembles Ovalopodium carrikeri Sawyer, 1980, a himatismenid that is believed to possess a scaleless, fuzzy or hairy "glycocalyx". We suggest that O. carrikeri might have been a similar species that lost scales under fixation. Our finding makes desirable a re-investigation of the genus Ovalopodium.

Animals↗