Rolf Dr. Michel - Academia.edu (original) (raw)

Papers by Rolf Dr. Michel

Research paper thumbnail of Isolation of Thecamoeba terricola from bark of Platanus occi-dentalis harbouring spore-forming eukaryotic endoparasites with intranuclear development

Samples of the bark from a Sycamore tree at Andernach were transferred to NNagar plates. From a m... more Samples of the bark from a Sycamore tree at Andernach were transferred to NNagar plates. From a mixed population of various freeliving amoebae (FLA), few trophozoites of Thecamoeba terricola obviously harbouring intranuclear parasites were isolated. Since all of the original host amoebae were prone to death by massive infections, spores were successfully transferred to a laboratory strain of T. quadrilineata which served as a substitute host of the parasites called “KTt1” and enabled all following studies. Electron microscopical studies confirmed the exclusive location of the parasites within the nucleus. After uptake by phagocytosis the spores get into the nucleus where they grow and develop over young stages within the endosome into large parasites occupying the whole interior of the nucleus while stretching the nuclear membrane. At this stage they differentiate into round or oval spores of 1.5 – 1.8 μm in diameter. The spores were enveloped by a double wall and contained in addit...

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Research paper thumbnail of Ultrastructure, SSU rRNA Gene Sequences and Phylogenetic Relationships of Flamella Schaeffer, 1926 (Amoebozoa), with Description of Three New Species

We isolated and described three new freshwater amoebozoan species that could be unambiguously ass... more We isolated and described three new freshwater amoebozoan species that could be unambiguously assigned to the genus Flamella Schaeffer, 1926 by light microscopy. The phylogenetic position of the genus Flamella within the Amoebozoa was unknown, and gene sequence data were lacking. We sequenced the SSU rRNA gene of five Flamella spp., including a previously described F. aegyptia Michel et Smirnov, 1999. The phylogenetic trees inferred from these data showed, that Flamella is monophyletic and robustly branches within Amoebozoa. It belongs to a clade comprising Filamoeba spp., ''Arachnula'' sp., some protostelids and several SSU rRNA sequences of unidentified or uncultured eukaryotes. This clade consistently branched close to Archamoebae, Mycetozoa, Acramoeba dendroida and Multicilia marina; in contrast to the previous hypotheses, Flamella spp. did not show any relatedness either to Leptomyxida, or to Flabellinea. The ultrastructure of trophic amoebae and especially cysts of the species studied showed considerable similarity to Comandonia operculata Pernin et Pussard, 1979. We therefore suggest that Comandonia may be a junior synonym of Flamella, although more ultrastructural data about Comandonia operculata are necessary to test this hypothesis.

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Research paper thumbnail of Chlamydial endocytobionts of free-living amoebae differentially affect the growth rate of their hosts

European Journal of Protistology, 2004

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Research paper thumbnail of The genus Sappinia: History, phylogeny and medical relevance

Experimental Parasitology, 2010

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Research paper thumbnail of Electron microscopical investigations of a new species of the genus Sappinia (Thecamoebidae, Amoebozoa), Sappinia platani sp. nov., reveal a dictyosome in this genus

Acta Protozoologica, 2014

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Research paper thumbnail of PARE-S-14-01075

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Research paper thumbnail of A Molecular Biological Approach to the Phylogenetic Position of the Genus Hyperamoeba

The Journal of Eukaryotic Microbiology, 2004

In 1923 Alexeieff described a new amoebic species within a new genus and named it Hyperamoeba fla... more In 1923 Alexeieff described a new amoebic species within a new genus and named it Hyperamoeba flagellata. This amoeba exhibits three life cycle stages, an amoeboid trophozoite, a flagellated stage, and a cyst-like the heteroloboseans, the mastigamoebae, and several slime moulds. Since then more strains have been isolated and relationships to the protostelids and cercomonads and to the myxogastrid plasmodial slime moulds have been suggested. However, up to now the classification and phylogenetic position of the hyperamoebae has remained unclear. The aim of our study was to make an approach to the phylogeny of the genus Hyperamoeba with combined morphological and molecular biological data. Since 1988 we have isolated and collected Hyperamoeba-like strains from different aquatic and terrestrial sources. The 18S rDNA-sequences of 8 new Hyperamoeba strains isolated from various habitats were analysed and a cluster analysis was performed including all other available hyperamoebae. Altogether, the results of our study corroborate the relatedness of Hyperamoeba to various slime moulds. However, the hyperamoebae do not seem to be a monophyletic group, clearly putting the validity of the genus Hyperamoeba into question.

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Research paper thumbnail of Rediscovery of Nucleophaga amoebae, a novel member of the Rozellomycota

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Research paper thumbnail of Microsporidia-like parasites of amoebae belong to the early fungal lineage Rozellomycota

Parasitology Research, 2014

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Research paper thumbnail of Rediscovery of Nucleophaga amoebae, a novel member of the Rozellomycota

Parasitol res, 2014

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Research paper thumbnail of “Candidatus Mesochlamydia elodeae” (Chlamydiae: Parachlamydiaceae), a novel chlamydia parasite of free-living amoebae

Parasitology Research, 2013

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Research paper thumbnail of Microsporidia-like parasites of amoebae belong to the early fungal lineage Rozellomycota

Parasitology Research, 2014

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Research paper thumbnail of Molecular identification of a phage-infected Protochlamydia strain naturally harboured by non-encysting Naegleria

Acta Protozoologica, 2013

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Research paper thumbnail of Rediscovery of Nucleophaga amoebae, a novel member of the Rozellomycota

Parasitol res, 2014

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Research paper thumbnail of Saccamoeba lacustris, sp. nov. (Amoebozoa: Lobosea: Hartmannellidae), a new lobose amoeba, parasitized by the novel chlamydia ‘Candidatus Metachlamydia lacustris’ (Chlamydiae: Parachlamydiaceae)

European Journal of Protistology, 2010

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Research paper thumbnail of Measurement of the Long-Lived Radionuclides Beryllium10, Carbon14 and Aluminum26 in Meteorites from Hot and Cold Deserts by Accelerator Mass Spectrometry (AMS)

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Research paper thumbnail of Radioecology of Iodine129: From Sea to Land

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Research paper thumbnail of UNTERSUCHUNGEN ZUR STRAHLENEXPOSITION DURCH NATÜRLICHE RADIONUKLIDE AUS DEM STEINKOHLEBERGBAU IN DER VORFLUT INVESTIGATIONS OF THE RADIATION EXPOSURE CAUSED BY AQUATIC RELEASES OF NATURAL RADIONUCLIDES FROM COALMINING

Summary In underground mine-waters of coal-mines precipitation of barium sulfate can occur with c... more Summary In underground mine-waters of coal-mines precipitation of barium sulfate can occur with co- precipitation of the natural radionuclides 226Ra and 228Ra. Although most of the residue re- mains underground, 226Ra and 228Ra are found in the effluents released into rivers and are transported further on. Based on the Basic Safety Standards the river Lippe was choosen as an example

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Research paper thumbnail of Ten New Meteorites from the Tenere Desert (Niger): Classification, Noble Gases, Cosmogenic Radionuclides and Terrestrial Ages

Schultz, L.; Scherer, P.; Spettel, B.; Wlotzka, F.; Zipfel, J.; Schluter, J.; Merchel, S.; Herper... more Schultz, L.; Scherer, P.; Spettel, B.; Wlotzka, F.; Zipfel, J.; Schluter, J.; Merchel, S.; Herpers, U.; Newton, J.; Franchi, IA; Pillinger, CT; Leya, I.; Neumann, S.; Neupert, U.; Michel, R.; Kubik, PW; Synal, H.-A.; Bonani, G.; Hajdas, I.; Ivy-Ochs, S.; Suter, M.

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Research paper thumbnail of Cross sections for the proton-induced production of He and Ne isotopes from magnesium, aluminum, and silicon

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1998

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Research paper thumbnail of Isolation of Thecamoeba terricola from bark of Platanus occi-dentalis harbouring spore-forming eukaryotic endoparasites with intranuclear development

Samples of the bark from a Sycamore tree at Andernach were transferred to NNagar plates. From a m... more Samples of the bark from a Sycamore tree at Andernach were transferred to NNagar plates. From a mixed population of various freeliving amoebae (FLA), few trophozoites of Thecamoeba terricola obviously harbouring intranuclear parasites were isolated. Since all of the original host amoebae were prone to death by massive infections, spores were successfully transferred to a laboratory strain of T. quadrilineata which served as a substitute host of the parasites called “KTt1” and enabled all following studies. Electron microscopical studies confirmed the exclusive location of the parasites within the nucleus. After uptake by phagocytosis the spores get into the nucleus where they grow and develop over young stages within the endosome into large parasites occupying the whole interior of the nucleus while stretching the nuclear membrane. At this stage they differentiate into round or oval spores of 1.5 – 1.8 μm in diameter. The spores were enveloped by a double wall and contained in addit...

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Research paper thumbnail of Ultrastructure, SSU rRNA Gene Sequences and Phylogenetic Relationships of Flamella Schaeffer, 1926 (Amoebozoa), with Description of Three New Species

We isolated and described three new freshwater amoebozoan species that could be unambiguously ass... more We isolated and described three new freshwater amoebozoan species that could be unambiguously assigned to the genus Flamella Schaeffer, 1926 by light microscopy. The phylogenetic position of the genus Flamella within the Amoebozoa was unknown, and gene sequence data were lacking. We sequenced the SSU rRNA gene of five Flamella spp., including a previously described F. aegyptia Michel et Smirnov, 1999. The phylogenetic trees inferred from these data showed, that Flamella is monophyletic and robustly branches within Amoebozoa. It belongs to a clade comprising Filamoeba spp., ''Arachnula'' sp., some protostelids and several SSU rRNA sequences of unidentified or uncultured eukaryotes. This clade consistently branched close to Archamoebae, Mycetozoa, Acramoeba dendroida and Multicilia marina; in contrast to the previous hypotheses, Flamella spp. did not show any relatedness either to Leptomyxida, or to Flabellinea. The ultrastructure of trophic amoebae and especially cysts of the species studied showed considerable similarity to Comandonia operculata Pernin et Pussard, 1979. We therefore suggest that Comandonia may be a junior synonym of Flamella, although more ultrastructural data about Comandonia operculata are necessary to test this hypothesis.

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Research paper thumbnail of Chlamydial endocytobionts of free-living amoebae differentially affect the growth rate of their hosts

European Journal of Protistology, 2004

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Research paper thumbnail of The genus Sappinia: History, phylogeny and medical relevance

Experimental Parasitology, 2010

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Electron microscopical investigations of a new species of the genus Sappinia (Thecamoebidae, Amoebozoa), Sappinia platani sp. nov., reveal a dictyosome in this genus

Acta Protozoologica, 2014

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Research paper thumbnail of PARE-S-14-01075

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Molecular Biological Approach to the Phylogenetic Position of the Genus Hyperamoeba

The Journal of Eukaryotic Microbiology, 2004

In 1923 Alexeieff described a new amoebic species within a new genus and named it Hyperamoeba fla... more In 1923 Alexeieff described a new amoebic species within a new genus and named it Hyperamoeba flagellata. This amoeba exhibits three life cycle stages, an amoeboid trophozoite, a flagellated stage, and a cyst-like the heteroloboseans, the mastigamoebae, and several slime moulds. Since then more strains have been isolated and relationships to the protostelids and cercomonads and to the myxogastrid plasmodial slime moulds have been suggested. However, up to now the classification and phylogenetic position of the hyperamoebae has remained unclear. The aim of our study was to make an approach to the phylogeny of the genus Hyperamoeba with combined morphological and molecular biological data. Since 1988 we have isolated and collected Hyperamoeba-like strains from different aquatic and terrestrial sources. The 18S rDNA-sequences of 8 new Hyperamoeba strains isolated from various habitats were analysed and a cluster analysis was performed including all other available hyperamoebae. Altogether, the results of our study corroborate the relatedness of Hyperamoeba to various slime moulds. However, the hyperamoebae do not seem to be a monophyletic group, clearly putting the validity of the genus Hyperamoeba into question.

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Research paper thumbnail of Rediscovery of Nucleophaga amoebae, a novel member of the Rozellomycota

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Microsporidia-like parasites of amoebae belong to the early fungal lineage Rozellomycota

Parasitology Research, 2014

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Research paper thumbnail of Rediscovery of Nucleophaga amoebae, a novel member of the Rozellomycota

Parasitol res, 2014

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Research paper thumbnail of “Candidatus Mesochlamydia elodeae” (Chlamydiae: Parachlamydiaceae), a novel chlamydia parasite of free-living amoebae

Parasitology Research, 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Microsporidia-like parasites of amoebae belong to the early fungal lineage Rozellomycota

Parasitology Research, 2014

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Research paper thumbnail of Molecular identification of a phage-infected Protochlamydia strain naturally harboured by non-encysting Naegleria

Acta Protozoologica, 2013

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Research paper thumbnail of Rediscovery of Nucleophaga amoebae, a novel member of the Rozellomycota

Parasitol res, 2014

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Research paper thumbnail of Saccamoeba lacustris, sp. nov. (Amoebozoa: Lobosea: Hartmannellidae), a new lobose amoeba, parasitized by the novel chlamydia ‘Candidatus Metachlamydia lacustris’ (Chlamydiae: Parachlamydiaceae)

European Journal of Protistology, 2010

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Research paper thumbnail of Measurement of the Long-Lived Radionuclides Beryllium10, Carbon14 and Aluminum26 in Meteorites from Hot and Cold Deserts by Accelerator Mass Spectrometry (AMS)

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Radioecology of Iodine129: From Sea to Land

Bookmarks Related papers MentionsView impact

Research paper thumbnail of UNTERSUCHUNGEN ZUR STRAHLENEXPOSITION DURCH NATÜRLICHE RADIONUKLIDE AUS DEM STEINKOHLEBERGBAU IN DER VORFLUT INVESTIGATIONS OF THE RADIATION EXPOSURE CAUSED BY AQUATIC RELEASES OF NATURAL RADIONUCLIDES FROM COALMINING

Summary In underground mine-waters of coal-mines precipitation of barium sulfate can occur with c... more Summary In underground mine-waters of coal-mines precipitation of barium sulfate can occur with co- precipitation of the natural radionuclides 226Ra and 228Ra. Although most of the residue re- mains underground, 226Ra and 228Ra are found in the effluents released into rivers and are transported further on. Based on the Basic Safety Standards the river Lippe was choosen as an example

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Research paper thumbnail of Ten New Meteorites from the Tenere Desert (Niger): Classification, Noble Gases, Cosmogenic Radionuclides and Terrestrial Ages

Schultz, L.; Scherer, P.; Spettel, B.; Wlotzka, F.; Zipfel, J.; Schluter, J.; Merchel, S.; Herper... more Schultz, L.; Scherer, P.; Spettel, B.; Wlotzka, F.; Zipfel, J.; Schluter, J.; Merchel, S.; Herpers, U.; Newton, J.; Franchi, IA; Pillinger, CT; Leya, I.; Neumann, S.; Neupert, U.; Michel, R.; Kubik, PW; Synal, H.-A.; Bonani, G.; Hajdas, I.; Ivy-Ochs, S.; Suter, M.

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Research paper thumbnail of Cross sections for the proton-induced production of He and Ne isotopes from magnesium, aluminum, and silicon

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1998

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