[At the background of ecological parasitology].

The data on scientific and teaching activities of A. A. Filipchenko, doctor of medicine and scientist-parasitologist, one of the founders of ecological parasitology in Russia is presented in this article. His fate and participation in the formation of this biological discipline were concealed for a long time. One of the reasons for this situation is the destruction of the scientist in 1938 during the course of mass repressions performed by Soviet State against its own citizens.

Nocodazole inhibits macronuclear infection with Holospora obtusa in Paramecium caudatum.

Holospora obtusa is a Gram-negative bacterium inhabiting the macronucleus of the ciliate Paramecium caudatum. Experimental infection with H. obtusa was carried out under nocodazole treatment. Nocodazole has been shown to cause disassembly of the cytoplasmic microtubules radiating from the cytopharynx and postoral fibers in P. caudatum. Treatment with this drug did not prevent the ingestion of both prey bacteria and H. obtusa, but it reduced the phagosome number and affected cyclosis. In situ hybridization revealed infectious forms of this endobiont very close to the macronucleus, but never inside it. These results indicate that disassembly of microtubules does not impair transportation of the infectious forms of H. obtusa in the cytoplasm, but that it completely blocks the invasion of the nucleus by the bacteria.

Spirostomum spp. (Ciliophora, Protista), a suitable system for endocytobiosis research.

Among ciliate genera, only Paramecium and Euplotes species have been studied extensively as host organisms of bacterial endocytobionts. In this article, we show that members of the genus Spirostomum may also serve as a suitable system for endocytobiosis research. Two strains of Spirostomum minus (Heterotrichea, Ciliophora) collected in Germany and Italy, respectively, were found to harbor different types of bacterial infections. Bacteria of various sizes and shapes were observed in the cytoplasm or in the nuclei of the ciliates. The bacteria in the cytoplasm were either surrounded by a peribacterial membrane or lay naked. One of the bacterial species was found in the vicinity of the contractile fibrillar system (myonemes) of the ciliates. In rare cases, another type of bacteria was observed associated with mitochondria. The macronuclei of both the Italian and the German strains were crowded with endocytobionts. The endonuclear bacteria in the two S. minus strains differed with respect to their cytoplasmic structures but they were of similar size and both were rod shaped. According to the results of in situ hybridization, the endonuclear bacteria of the Italian strain belong to the subgroup of alphaproteobacteria, whereas the bacteria associated with the fibrillar system appeared to be gram-positive bacteria with high G+C content. While both the German and the Italian strains were found to permanently maintain their endocytobionts, they were at least partly colonized by different bacteria. This is taken as an indication that geographically separated populations of ciliates may be stably infected by different endocytobionts, possibly due to different ecological conditions. For S. minus and S. ambiguum a total of 7 different bacterial endocytobionts have now been recorded. We recommend the members of the genus Spirostomum as a suitable system for endocytobiosis research.

Initial steps of infection of the ciliate Paramecium with bacteria Holospora sp.

New light and electron microscope data on the initial steps of endocytobiosis establishment between the ciliate Paramecium and specific intranuclear bacteria Holospora are provided. At the cytoplasmic step of infection bacteria of all Holospora species are found in a vesicle originating from the membrane of the host cell phagosome. The association between host cell microfilaments and the bacterium bearing vesicle may suggest a possible involvement of the ciliate cytoskeleton in the transportation of bacteria to the host cell nucleus. The authors subdivide the process of infection into 6 steps. Some strains of P. caudatum never take up infectious Holospora bacteria in the course of phagocytosis.

[The route of a bacterium Holospora in the cell of Paramecium (Ciliophora, Protista) from phagosome to the nucleus]. / Put' bakterii Holospora v kletke Paramecium (Ciliophora, Protista) ot fagosomy do iadra.

Problems encountered at the initial stages of stable symbiotic system formation are discussed in the review. The most studied models for interaction between pathogenic bacteria and metazoan cells are compared with a similar system including Paramecium (a ciliatte)--Holospora (a bacterium). Literary and our own data on the infection of P. caudatum with specific endocytobionts inhabiting the nuclear apparatus (H. obtusa in the macronucleus), and H. undulata (in the micronucleus) are analysed with respect to the modern understanding of the intracellular vesicle trafficking.

Characterization of intracytoplasmic prokaryote infections in Dreissena sp. (Bivalvia: Dreissenidae).

This study characterizes intracytoplasmic infections with prokaryote microorganisms in Dreissena sp. (near Dreissena polymorpha) from northeastern Greece and represents the first report of such infections in freshwater bivalves. Light microscope observations of stained tissues revealed basophilic, cytoplasmic inclusion bodies in 87.5% (28/32) of the mussels sectioned. Inclusions in epithelial cells and connective tissues were noted, respectively, in 34.4 and 71.9% of the sample, with 5 mussels (15.6%) having both tissue types infected. Epithelial cell infections were observed in histological sections only in digestive gland tubules and ducts; within tubules, inclusions were present more often in secretory than digestive cells. Connective tissue infections, however, were systemic; among the 32 mussels sectioned, inclusions were found in the gills (65.6%), foot (12.5%), mantle (9.4%), labial palps (6.3%), digestive gland (6.3%), stomach (6.3%), and gonads (3.1%). Cytoplasmic inclusions (maximum dimension, 138 microm) were prominent enough in the gills to be visible in 17.0% of the 247 mussels dissected. Ultrastructurally, prokaryote cells in gill connective tissues were clearly characteristic of Chlamydiales-like organisms, with each intracytoplasmic inclusion containing a loosely packed mixture of elementary, reticulate, intermediate bodies, and blebs. Prokaryote colonies in digestive gland epithelial cells exclusively contained 1 of 4 morphological cell types and were considered Rickettsiales-like. Hexagonal, virus-like particles were present in the cytoplasm of the largest of these Rickettsiales-like prokaryotes. Although host stress was evident from localized cell necrosis and dense hemocyte infiltration, overall infection was fairly benign, with no major, adverse impact on body condition evident among sectioned or dissected mussels. A possible negative effect was partial constriction of gill water tubes, but at the infection intensity observed (typical range 1 to 7 inclusion bodies per section), significant interference with respiration and other metabolic functions of the gills was highly unlikely.

Phylogenetic relationships of the genus Paramecium inferred from small subunit rRNA gene sequences.

The genus Paramecium includes species that are well known and very common in freshwater environments. Species of Paramecium are morphologically divided into two distinct groups: the "bursaria" subgroup (foot-shaped) and the "aurelia" subgroup (cigar-shaped). Their placement within the class Oligohymenophorea has been supported by the analysis of the small subunit rRNA gene sequence of P. tetraurelia. To confirm the stability of this placement and to resolve relationships within the genus, small subunit rRNA gene sequences of P. bursaria, P. calkinsi, P. duboscqui, P. jenningsi, P. nephridiatum, P. primaurelia, and P. polycaryum were determined and aligned. Trees constructed using distance-matrix, maximum-likelihood, and maximum-parsimony methods all depicted the genus as a monophyletic group, clustering with the other oligohymenophorean taxa. Within the Paramecium clade, P. bursaria branches basal to the other species, although the remaining species of the morphologically defined "bursaria" subgroup do not group with P. bursaria, nor do they form a monophyletic subgroup. However, the species of the "aurelia" subgroup are closely related and strongly supported as a monophyletic group.

Phylogenetic relationships of the Subclass Peniculia (Oligohymenophorea, Ciliophora) inferred from small subunit rRNA gene sequences.

Peniculine ciliates have been recognized as a distinct higher taxon of ciliates for almost 50 years. However, phylogenetic relationships within the Subclass Peniculia are still unsettled. To contribute to our understanding of their phylogeny and provide evidence for the position of Urocentrum turbo, we sequenced its small subunit (SS) rRNA gene and the SSrRNA genes from Lembadion bullinum, Frontonia sp., Paramecium caudatum, Paramecium multimicronucleatum, Paramecium putrinum, and Paramecium woodruffi. Urocentrum turbo was the only one of these species not to exhibit a shortened Helix E10_1, which we conclude characterizes the "higher" peniculines. Except for U. turbo, the peniculines are strongly supported as a monophyletic clade with Lembadion, Frontonia, and Paramecium species forming separate and strongly supported clades by bootstrap analysis using distance matrix, maximum parsimony, and maximum likelihood methods. Urocentrum turbo is associated with different lineages, depending upon the analysis used. The Paramecium species form at least four clades with the Paramecium aurelia subgroup being the most derived. We conclude that the Subclass Peniculia should be divided into two orders, the Order Urocentrida and Order Peniculida, with the latter order having two suborders, the Suborder Frontoniina and Peniculina. We place U. turbo with the peniculines because of shared morphological and stomatogenetic features.

[Effect of local UV irradiation of the generative nucleus on the vegetative functions of the infusorian, Paramecium putrinum]. / Vliianie lokal'nogo UF oblucheniia generativnogo iadra na vegetativnye funktsii infuzorii Paramecium putrinum.

The influence of the generative nucleus on the vitality in three clones of Paramecium putrinum was studied. The selective functional inactivation of the micronucleus (MI) was achieved with a local ultraviolet microbeam. After irradiation of micronuclei these soon disappeared and the irradiated cells perished shortly afterwards. In the part of UV treated-subclones the macronucleus (MA) fragmentation was discovered. It is possible that the fragments of MA are some kind of functional replacement of the lost or damaged generative nucleus. That data obviously demonstrate the function of MI of P. putrinum during its vegetative growth.

[Effect of local UV microirradiation on the nuclear apparatus and cytoplasm of the infusorian Paramecium caudatum]. / Vliianie lokal'nogo UF mikrooblucheniia na iadernyi apparat i tsitoplazmu infuzorii Paramecium caudatum

The work is the first attempt to study nuclear dualism of ciliates with ultraviolet microbeam (UV-beam), which was not applied earlier for these purposes. The special advantage of the UV-beam is that it allow to inactivate selectively of the particular elements of nuclear apparatus of living ciliates is to observe consequences of operation on distant descendants of irradiated cell. On Paramecium caudatum the ways of UV-beam have been devised specifically. The original rotocompression chamber was employed for immobilization of cell in space of irradiation. The effective UV-doses were selected, the relative resistance of cytoplasm, macro-, micronucleus (Mi), and symbiotic bacteria of Mi -- omega particles -- was detected. The "pure" and infected cells were irradiated, in some different variants. The effect of UV-beam depends on dose and consists in a reduction the effectiveness of cell cloning, the loss of omega-particles from Mi, the appearance of the cells with 2--3 Mi, and, possibly, of amicronucleate cells. The injuries due to UV-beam are restored by photoreactivation of visible light.