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  • Endosymbiosis
  • Springer  (44)
  • Public Library of Science (PLoS)  (1)
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  • 1
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    Public Library of Science (PLoS)
    Publication Date: 2022-05-25
    Description: © 2004 Jennifer J. Wernegreen. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The definitive version was published in PLoS Biology 2 (2004): e68, doi:10.1371/journal.pbio.0020068.
    Description: Symbiosis, an interdependent relationship between two species, is an important driver of evolutionary novelty and ecological diversity. Microbial symbionts in particular have been major evolutionary catalysts throughout the 4 billion years of life on earth and have largely shaped the evolution of complex organisms. Endosymbiosis is a specifi c type of symbiosis in which one—typically microbial—partner lives within its host and represents the most intimate contact between interacting organisms. Mitochondria and chloroplasts, for example, result from endosymbiotic events of lasting significance that extended the range of acceptable habitats for life. The wide distribution of intracellular bacteria across diverse hosts and marine and terrestrial habitats testifies to the continued importance of endosymbiosis in evolution. Among multicellular organisms, insects as a group form exceptionally diverse associations with microbial associates, including bacteria that live exclusively within host cells and undergo maternal transmission to offspring. These microbes have piqued the interest of evolutionary biologists because they represent a wide spectrum of evolutionary strategies, ranging from obligate mutualism to reproductive parasitism (Buchner 1965; Ishikawa 2003) (Box 1; Table 1).
    Description: JJW gratefully acknowledges the support of the National Institutes of Health (R01 GM62626-01), the National Science Foundation (DEB 0089455), the National Aeronautics and Space Administration Astrobiology Institute (NNA04CC04A), and the Josephine Bay Paul and C. Michael Paul Foundation.
    Keywords: Endosymbiosis ; Endosymbiosis manipulation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Molecular genetics and genomics 263 (2000), S. 152-158 
    ISSN: 1617-4623
    Keywords: Key words Minicircle ; Dinoflagellate ; Plastid DNA ; Codon bias ; Endosymbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plastid DNA was purified from the dinoflagellate Amphidinium operculatum. The genes atpB, petD, psaA, psbA and psbB have been shown to reside on single-gene minicircles of a uniform size of 2.3–2.4 kb. The psaA and psbB genes lack conventional initiation codons in the expected positions, and may use GTA for translation initiation. There are marked biases in codon preference. The predicted PsbA protein lacks the C-terminal extension which is present in all other photosynthetic organisms except Euglena gracilis, and there are other anomalies elsewhere in the predicted amino acid sequences. The non-coding regions of the minicircles contain a “core” region which includes a number of stretches that are highly conserved across all minicircles and modular regions that are conserved within subsets of the minicircles.
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  • 3
    ISSN: 1615-6102
    Keywords: Chlorella sp. ; Endosymbiosis ; Infection ; Paramecium bursaria ; Paraquat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The green parameciumParamecium bursaria has many endosymbiotic algae in its cytoplasm. Here, we cloned and characterized endosymbiotic algae fromP. bursaria and examined in detail the interaction between the cloned algae and algae-free paramecia. Homogenates ofP. bursaria were cultured on agar plates containing various kinds of media to establish clones of the endosymbiotic algae. Many algal colonies were obtained from poorly nutritious medium (CA medium) after one month in culture. Algae were picked up from these colonies and inoculations were repeated 9 times on agar plates containing CA medium. On enriched media including bacto-peptone, glucose, proteose-peptone and/or yeast extract, however, bacteria and mold grew rapidly and no algal colonies were formed. When the cloned algae were cultured in liquid CA medium, they grew faster than on agar plates and the numbers stayed constant at 1 × 107 algae/ml after 7 days in culture. They revealed high infectivity to algae-free paramecia, and an incubation period of 24 h and at least 1 × 103 algae/paramecium were required to achieve successful infection (80–90%). The growth and infection rate did not change through 74 repeated inoculations of algae in liquid CA medium. Optical microscopic observations revealed marked morphological similarity between endosymbiotic algae and free-livingChlorella, but the latter showed no infectivity to algae-free paramecia. The cloned endosymbiotic algae presented here will provide an excellent opportunity to examine the mechanism of symbiont-host interaction.
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  • 4
    ISSN: 1432-0983
    Keywords: Key wordsEuglena gracilis ; Endosymbiosis ; Endosymbiotic gene transfer ; Molecular evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthetic protist Euglena gracilis is one of few organisms known to possess both class-I and class-II fructose-1,6-bisphosphate aldolases (FBA). We have isolated cDNA clones encoding the precursor of chloroplast class-I FBA and cytosolic class-II FBA from Euglena. Chloroplast class-I FBA is encoded as a single subunit rather than as a polyprotein, its deduced transit peptide of 139 amino acids possesses structural motifs neccessary for precursor import across Euglena's three outer chloroplast membranes. Evolutionary analyses reveal that the class-I FBA of Euglena was recruited to the chloroplast independently from the chloroplast class-I FBA of chlorophytes and may derive from the cytosolic homologue of the secondary chlorophytic endosymbiont. Two distinct subfamilies of class-II FBA genes are shown to exist in eubacteria, which can be traced to an ancient gene duplication which occurred in the common ancestor of contemporary gram-positive and proteobacterial lineages. Subsequent duplications involving eubacterial class-II FBA genes resulted in functional specialization of the encoded products for substrates other than fructose-1,6-bisphosphate. Class-II FBA genes of Euglena and ascomycetes are shown to be of eubacterial origin, having been acquired via endosymbiotic gene transfer, probably from the antecedants of mitochondria. The data provide evidence for the chimaeric nature of eukaryotic genomes.
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  • 5
    ISSN: 1432-0983
    Keywords: Key words Chloroplast ; Mitochondria ; Endosymbiosis ; Endosymbiotic gene transfer ; Calvin cycle ; Glycolysis ; Evolution ; Amitochondriate ; Metabolism ; Compartmentation ; Hydrogenosome ; Eukaryote ; Origin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The evolutionary histories of the 12 enzymes that catalyze the reactions of the Calvin cycle in higher-plant chloroplasts are summarized. They are shown to be encoded by a mixture of nuclear genes of cyanobacterial and proteobacterial origin. Moreover, where cytosolic isoforms of these enzymes are found they are almost invariably encoded by genes of clearly endosymbiont origin. We infer that endosymbiosis resulted in functional redundancy that was eliminated through differential gene loss, with intruding eubacterial genes repeatedly replacing pre-existing nuclear counterparts to which they were either functionally or structurally homologous. Our findings fail to support the `product-specificity corollary', which predicts re-targeting of nuclear-encoded gene products to the organelle from whose genome they originated. Rather it would appear that the enzymes of central carbohydrate metabolism have evolved novel targeting possibilities regardless of their origins. Our findings suggest a new hypothesis to explain organelle genome persistence, based on the testable idea that some organelle-encoded gene products might be toxic when present in the cytosol or other inappropriate cellular compartments.
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  • 6
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    Journal of molecular evolution 42 (1996), S. 482-492 
    ISSN: 1432-1432
    Keywords: Aging ; Chloroplasts ; Mitochondria ; Cell evolution ; Cytoplasmic genomes ; Gene transfer ; Redox regulation ; Free radical mutagenesis ; Nitrogen fixation ; Endosymbiosis ; Mutation frequency ; Uniparental inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The prokaryotic endosymbionts that became plastids and mitochondria contained genes destined for one of three fates. Genes required for free-living existence were lost. Most genes useful to the symbiosis were transferred to the nucleus of the host. Some genes, a small minority, were retained within the organelle. Here we suggest that a selective advantage of movement of genes to the nucleus is decreased mutation: plastids and mitochondria have high volume-specific rates of redox reactions, producing oxygen free radicals that chemically modify DNA. These mutations lead to synthesis of modified electron carriers that in turn generate more mutagenic free radicals—the “vicious circle” theory of aging. Transfer of genes to the nucleus is also advantageous in facilitating sexual recombination and DNA repair. For genes encoding certain key components of photosynthesis and respiration, direct control of gene expression by redox state of electron carriers may be required to minimize free radical production, providing a selective advantage of organelle location which outweighs that of location in the nucleus. A previous proposal for transfer of genes to the nucleus is an economy of resources in having a single genome and a single apparatus for gene expression, but this argument fails if any organellar gene is retained. A previous proposal for the retention of genes within organelles is that certain proteins are organelle-encoded because they cannot be imported, but there is now evidence against this view. Decreased free radical mutagenesis and increased sexual recombination upon transfer to the nucleus together with redox control of gene expression in organelles may now account for the slightly different gene distributions among nuclei, plastids, and mitochondria found in major eukaryote taxa. This analysis suggests a novel reason for uniparental inheritance of organelles and the evolution of anisogametic sex, and may also account for the occurrence of nitrogen fixation in symbionts rather than in nitrogen-fixing organelles.
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  • 7
    ISSN: 1615-6102
    Keywords: Cyanobacteria ; Endocytobiosis ; Endosymbiosis ; Geosiphon ; Nostoc ; Phagocytosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Phagocytosis ofNostoc filaments byGeosiphon, a fungus closely related to AM forming Glomales, was observed under light microscopes. Incorporation can only be performed ifNostoc primordia come into contact with growing hyphal tips of the fungus. The fungal wall just below the apex softens, and fungal cytoplasm is bulged out repeatedly covering the vegetativeNostoc cells but not the heterocytes. New heterocytes are differentiated by the internalised filament whose cells can increase up to ten times in volume after recovering from incorporation strain. TheNostoc cells are coated stepwise by short finger-shaped protuberances of the fungal hypha. These hernia-like outgrowths first remain separated, after 1 to 2 days they merge. Adjacent hyphal walls inside the complex covering disintegrate. Periphal fungal wall portions are united to form a smooth strong outer envelope. Internalisation is categorised as phagocytosis. The partnership is partly specific,Nostoc strains capable of living endocytobiotically are often partners in other symbioses besidesGeosiphon.
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  • 8
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    Journal of molecular evolution 41 (1995), S. 727-731 
    ISSN: 1432-1432
    Keywords: Aphid ; Bacteria ; Buchnera ; Cospeciation ; Endosymbiosis ; Evolutionary rates ; Molecular clock ; Prokaryote ; Ribosomal DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The hypothesis of a universal molecular clock holds that divergent lineages exhibit approximately constant rates of nucleotide substitution over evolutionary time for a particular macromolecule. We compare divergences of ribosomal DNA for aphids (Insecta) and Buchnera, the maternally transmitted, endosymbiotic bacteria that have cospeciated with aphids since initially infecting them over 100 million years ago. Substitution rates average 36 times greater for Buchnera than for their aphid hosts for regions of small-subunit rDNA that are homologous for prokaryotes and eukaryotes. Aphids exhibit 18S rDNA substitution rates that are within the range observed in related insects. In contrast, 16S rDNA evolves about twice as fast in Buchnera as in related free-living bacterial lineages. Nonetheless, the difference between Buchnera and aphids is much greater, suggesting that rates may be generally higher in bacteria. This finding adds to evidence that molecular clocks are only locally rather than universally valid among taxonomic groups. It is consistent with the hypothesis that rates of sequence evolution depend on generation time.
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  • 9
    ISSN: 1432-1432
    Keywords: Cyanelles ; Cyanophora paradoxa ; Endosymbiosis ; Evolution ; Glaucocystophyta ; Glaucophyta ; Phylogeny ; Plastid ; 16S ribosomal RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glaucocystophyte algae (sensu Kies, Berl. Deutsch. Bot. Ges. 92, 1979) contain plastids (cyanelles) that retain the peptidoglycan wall of the putative cyanobacterial endosymbiont; this and other ultrastructural characters (e.g., unstacked thylakoids, phycobilisomes) have suggested that cyanelles are “primitive” plastids that may represent undeveloped associations between heterotrophic “host” cells (i.e., glaucocystophytes) and cyanobacteria. To test the monophyly of glaucocystophyte cyanelles and to determine their evolutionary relationship to other plastids, complete 16S ribosomal RNA sequences were determined for Cyanophora paradoxa, Glaucocystis nostochinearum, Glaucosphaera vacuolata, and Gloeochaete wittrockiana. Plastid rRNAs were analyzed with the maximum-likelihood, maximumparsimony, and neighbor joining methods. The phylogenetic analyses show that the cyanelles of C. paradoxa, G. nostochinearum, and G. wittrockiana form a distinct evolutionary lineage; these cyanelles presumably share a monophyletic origin. The rDNA sequence of G. vacuolata was positioned within the nongreen plastid lineage. This result is consistent with analyses of nuclear-encoded rRNAs that identify G. vacuolata as a rhodophyte and support its removal from the Glaucocystophyta. Results of a global search with the maximumlikelihood method suggest that cyanelles are the first divergence among all plastids; this result is consistent with a single loss of the peptidoglycan wall in plastids after the divergence of the cyanelles. User-defined tree analyses with the maximum-likelihood method indicate, however, that the position of the cyanelles is not stable within the rRNA phylogenies. Both maximumparsimony and neighbor-joining analyses showed a close evolutionary relationship between cyanelles and nongreen plastids; these phylogenetic methods were sensitive to inclusion/exclusion of the G. wittrockiana cyanelle sequence. Base compositional bias within the G. wittrockiana 16S rRNA may explain this result. Taken together the phylogenetic analyses are interpreted as supporting a near-simultaneous radiation of cyanelles and green and nongreen plastids; these organelles are all rooted within the cyanobacteria.
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  • 10
    ISSN: 1432-1432
    Keywords: Aphid ; Endosymbiosis ; Leucine operon ; Buchnera ; Plasmid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have identified and completely sequenced a novel plasmid isolated from the aphid Rhopalosiphum padi. Evidence which suggests that the plasmid occurs localized within the bacterial endosymbionts is presented. The plasmid contains the four genes that constitute the entire leucine operon. This fact makes it really unique since most plasmids are dispensable and lack genes that encode essential anabolic functions. Four more phloem-feeding aphid species also seem to contain homologous plasmids. Although further work is necessary, we hypothesize that this plasmid has appeared during the evolution of the symbiotic association between the aphid and the bacterial endosymbiont. The fact that this plasmid contains the entire leucine operon can be related to physiological evidence showing that the aphid host's diet of plant phloem is deficient in essential amino acids.
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  • 11
    ISSN: 1617-4623
    Keywords: ssDNA-binding protein Cyanobacteria ; Ribosomal protein S1 ; Endosymbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We isolated a 38 kDa ssDNA-binding protein from the unicellular cyanobacterium Synechococcus sp. strain PCC 6301 and determined its N-terminal amino acid sequence. A genomic clone encoding the 38 kDa protein was isolated by using a degenerate oligonucleotide probe based on the amino acid sequence. The nucleotide sequence and predicted amino acid sequence revealed that the 38 kDa protein is 306 amino acids long and homologous to the nuclear-encoded 370 amino acid chloroplast ribosomal protein CS1 of spinach (48% identity), therefore identifying it as ribosomal protein (r-protein) S1. Cyanobacterial and chloroplast S1 proteins differ in size from Escherichia coli r-protein S1 (557 amino acids). This provides an additional evidence that cyanobacteria are closely related to chloroplasts. The Synechococcus gene rps1 encoding S1 is located 1.1 kb downstream from psbB, which encodes the photosystem 11 P680 chlorophyll a apoprotein. An open reading frame encoding a potential protein of 168 amino acids is present between psbB and rps1 and its deduced amino acid sequence is similar to that of E. coli hypothetical 17.2 kDa protein. Northern blot analysis showed that rps1 is transcribed as a monocistronic mRNA.
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  • 12
    ISSN: 1432-1432
    Keywords: Aphids ; Endosymbiosis ; Symbionin ; Chaperonin 60 ; Chaperonin 10 ; Immunoblotting ; Immunohistochemistry ; Primary symbiont ; Secondary symbiont ; Endosymbiotic evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary All aphids harbor symbiotrophic prokaryotes (“primary symbionts”) in a specialized-abdominal cell, the bacteriocyte. Chaperonin 60 (Cpn60, symbionin) and chaperonin 10 (Cpn10), which are high and low molecular weight heatshock proteins, were sought in tissues of more than 60 aphid species. The endosymbionts were compared immunologically and histologically. It was demonstrated that (1) there are two types of aphids in terms of the endosymbiotic system: some with only primary symbionts and others with, in addition, secondary symbionts; (2) the primary symbionts of various aphids are quite similar in morphology whereas the secondary symbionts vary; and (3) irrespective of the aphid species, Cpn60 is abundant in both the primary and secondary symbionts, while Cpn10 is abundant in the secondary symbionts but present in small amounts in the primary ones. Based on these results, we suggest that the primary symbionts have been derived from a prokaryote that was acquired by the common ancestor of aphids whereas the secondary symbionts have been acquired by various aphids independently after divergence of the aphid species. In addition, we point out the possibility that the prokaryotes under intracellular conditions have been subject to some common evolutionary pressures, and as a result, have come to resemble cell organelles.
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  • 13
    ISSN: 1432-1432
    Keywords: 5S RNA ; 5S RNA genes ; Nucleotide sequence ; Secondary structure ; Chloroplast evolution ; Endosymbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The chloroplast 5S rRNA gene of the brown alga Pylaiella littoralis (L.) Kjellm has been cloned and sequenced. The gene is located 23 bp downstream from the 3′ end of the 23S rRNA gene. The sequence of the gene is as follows: GGTCTTG GTGTTTAAAGGATAGTGGAACCACATTGAT CCATATCGAACTCAATGGTGAAACATTATT ACAGTAACAATACTTAAGGAGGAGTCCTTT GGGAAGATAGCTTATGCCTAAGAC. A secondary structure model is proposed, and compared to those for the chloroplast 5S rRNAs of spinach and the red alga Porphyra umbilicalis. Cladograms based on chloroplast and bacterial 5S rRNA and rRNA gene sequences were constructed using the MacClade program with a user-defined character transformation in which transitions and transversions were assigned unequal step values. The topology of the resulting cladogram indicates a polyphyletic origin for photosynthetic organelles.
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  • 14
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    Journal of molecular evolution 35 (1992), S. 385-404 
    ISSN: 1432-1432
    Keywords: Endosymbiosis ; Molecular phylogeny ; Algal evolution ; Plastid origins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An overview of recent molecular analyses regarding origins of plastids in algal lineages is presented. Since different phylogenetic analyses can yield contradictory views of algal plastid origins, we have examined the effect of two distance measurement methods and two distance matrix tree-building methods upon topologies for the ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit nucleotide sequence data set. These results are contrasted to those from bootstrap parsimony analysis of nucleotide sequence data subsets. It is shown that the phylogenetic information contained within nucleotide sequences for the chloroplast-encoded gene for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, integral to photosynthesis, indicates an independent origin for this plastid gene in different plant taxa. This finding is contrasted to contrary results derived from 16S rRNA sequences. Possible explanations for discrepancies observed for these two different molecules are put forth. Other molecular sequence data which address questions of early plant evolution and the eubacterial origins of algal organelles are discussed.
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  • 15
    ISSN: 1432-1432
    Keywords: rbcLS ; Operon ; Rubisco ; Prochlorophyte ; Endosymbiosis ; Polyphyletic plastid origin ; Codon usage ; Chlorophyllb ; Phycobilins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Prochlorophytes similar toProchloron sp. andProchlorothrix hollandica have been suggested as possible progenitors of the plastids of green algae and land plants because they are prokaryotic organisms that possess chlorophyllb (chlb). We have sequenced theProchlorothrix genes encoding the large and small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco),rbcL andrbcS, for comparison with those of other taxa to assess the phylogenetic relationship of this species. Length differences in the large subunit polypeptide among all sequences compared occur primarily at the amino terminus, where numerous short gaps are present, and at the carboxy terminus, where sequences ofAlcaligenes eutrophus and non-chlorophyllb algae are several amino acids longer. Some domains in the small subunit polypeptide are conserved among all sequences analyzed, yet in other domains the sequences of different phylogenetic groups exhibit specific structural characteristics. Phylogenetic analyses ofrbcL andrbcS using Wagner parsimony analysis of deduced amino acid sequences indicate thatProchlorothrix is more closely related to cyanobacteria than to the green plastid lineage. The molecular phylogenies suggest that plastids originated by at least three separate primary endosymbiotic events, i.e., once each leading to green algae and land plants, to red algae, and toCyanophora paradoxa. TheProchlorothrix rubisco genes show a strong GC bias, with 68% of the third codon positions being G or C. Factors that may affect the GC content of different genomes are discussed.
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  • 16
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    Archives of microbiology 156 (1991), S. 327-334 
    ISSN: 1432-072X
    Keywords: Sapropelic ciliates ; Trimyema compressum ; Monoxenic culture ; Rubrivivax gelatinosus ; Fermentation products ; Anaerobiosis ; Microaerobiosis ; Methanogenic bacteria ; Endosymbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new monoxenic culture of the anaerobic ciliate Trimyema compressum was established on the purple nonsulfur bacterium Rubrivivax gelatinosus. Compared with the first monoxenic culture of T. compressum on a Bacteroides species no significant difference in growth rate was observed. Using both monoxenic cultures the fermentation products of the ciliate, acetate, lactate, formate and succinate were quantified. Ammonium was another product of the ciliates metabolism. The amount of the endproducts was dependent on the amount of bacteria consumed. The ratio of carbon consumed to ammonium formed was 8.7:1 indicating incomplete degradation of nitrogenous compounds of the bacterial biomass. Under microoxic conditions no effect of oxygen on the yield of the ciliate was observed but the amount of acetate and lactate was 25% lower. Cells of T. compressum with Methanobacterium formicicum as deliberately introduced endosymbiont did not form significantly different fermentation products, however, instead of formate methane was detected as product. The yield of the ciliate was not affected. It is concluded that methanogenic bacteria deliberately introduced into the cytoplasm of T. compressum as endosymbionts are pure commensalists.
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  • 17
    ISSN: 1432-0983
    Keywords: Endosymbiosis ; psbA ; Xanthophyceae ; Prochlorothrix ; Bumilleriopsis ; Eukaryotic algae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary When only plastidic features are considered, it is difficult to distinguish between monophyletic and polyphyletic xenogenous origins of plastids. We suggest that a direct comparison of nuclear and plastidic sequence-similarity pattern will help to solve this problem. The D1 amino acid sequence of six major groups of photosynthetic eukaryotes and of the two groups of photosynthetic prokaryotes are now available, including the psbA-gene product from Bumilleriopsis filiformis, which is the first molecular sequence reported for a xanthophycean alga. Evidence is provided for an independent and polyphyletic origin of plastids from five out of the six major taxa of photosynthetic eukaryotes. This conclusion is reached by comparing a plastid-based pattern of D1 similarity with a nucleus-based similarity pattern published recently. Furthermore, the availability of D1 sequences from five eukaryotic algae led to a re-evaluation of the taxonomic position of Prochlorothrix.
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  • 18
    ISSN: 1432-2048
    Keywords: Endosymbiosis ; Geosiphon ; Nostoc ; Photosynthesis in Geosiphon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Geosiphon pyriforme, an endosymbiotic association between a fungus and the cyanobacterium Nostoc, was shown by tracer studies to acquire carbon photosynthetically from CO2 or bicarbonate. The organism also fixes inorganic carbon in darkness, at lower rates than in the light. The patterns of label distribution are indicative of the operation of the reductive pentose-phosphate pathway in the light and of the phosphoenolpyruvate-carboxylase reaction in the dark. The results are discussed in relation to the evolution of photoautotrophic endosymbiotic associations.
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  • 19
    ISSN: 1432-1432
    Keywords: Chloroplast evolution ; Cyanelles ; Cyanophora paradoxa ; Euglena gracilis ; Endosymbiosis ; Land plants ; Phylogenetic tree ; Ribosomal protein genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nucleotide sequences of the ribosomal protein genesrps18, rps19, rpl2, rpl33, and partial sequence ofrpl22 from cyanelles, the photosynthetic organelles of the protistCyanophora paradoxa, have been determined. These genes form two clusters oriented in opposite and divergent directions. One cluster contains therpl33 andrps18 genes; the other contains therpl2, rps19, andrpl22 genes, in that order. Phylogenetic trees were constructed from both the DNA sequences and the deduced protein sequences of cyanelles,Euglena gracilis and land plant chloroplasts, andEscherichia coli, using parsimony or maximum likelihood methods. In addition, a phylogenetic tree was built from a distance matrix comparing the number of nucleotide substitutions per site. The phylogeny inferred from all these methods suggests that cyanelles fall within the chloroplast line of evolution and that the evolutionary distances between cyanelles and land plant chloroplasts are shorter than betweenE. gracilis chloroplasts and land plant chloroplasts.
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  • 20
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    Archives of microbiology 153 (1990), S. 496-501 
    ISSN: 1432-072X
    Keywords: Anaerobic ciliates ; Trimyema compressum ; Endosymbiosis ; Methanogenic bacteria ; Methanobacterium formicicum ; Incorporation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Monoxenic cultures of the anaerobic, endosymbiont-free ciliate Trimyema compressum were incubated with low numbers of Bacteroides sp. strain WoCb15 as food bacteria and two strains (DSM 3636 and 3637) of Methanobacterium formicicum, which originally had been isolated from the anaerobic protozoa Metopus striatus and Pelomyxapalustris. The ciliate which had lost its original endosymbiotic methanogens ingested both strains of M. formicicum. The methanogenic bacteria were found intact in large vacuoles in contrast to the food bacteria which were digested. Single methanogens were separated from the vacuoles and appeared surrounded by a membrane in the cytoplasm of the ciliate. After 2 months of incubation, the methanogenic bacteria still exhibited the typical bluish fluorescence and the new symbiotic association of M. formicicum and T. compressum excreted methane. Increasing the growth rate of the ciliates by large numbers of food bacteria resulted in a loss of the methanogenic bacteria, due to statistical outgrowth.
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  • 21
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    Archives of microbiology 153 (1990), S. 187-192 
    ISSN: 1432-072X
    Keywords: Anaerobic ciliates ; Anaerobiosis ; Endosymbiosis ; Hydrogenosomes ; Mitochondria ; Methanogenic bacteria ; Monoxenic culture ; Trimyema compressum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two strains of the anaerobic ciliate Trimyema compressum, isolated from different habitats, were compared. The cytoplasm of the ciliates contained hydrogenosome-like microbodies and methanogenic bacteria; the latter were lost during continued cultivation. In addition both strains harbored a non-methanogenic endosymbiont, which was lost in strain K. The ciliates lacked cytochromes, cytochrome oxidase and catalase but contained superoxide dismutase. Hydrogenase activity could be demonstrated only in strain N. In monoxenic culture strain K needed sterols as growth factors. The cells of both strains reacted similarly with respect to oxygen tolerance (up to 0.5 mg O2/l), inhibition of growth by cyanide and azide, and resistance to antimycin A. Only cells of strain N showed growth inhibition by chloramphenicol. It is concluded that Trimyema compressum is an anaerobic, microaerotolerant organism, its microbodies show more resemblance to hydrogenosomes than to mitochondria.
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  • 22
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    Current genetics 18 (1990), S. 199-202 
    ISSN: 1432-0983
    Keywords: Cyanelles ; Endosymbiosis ; Plastid evolution ; Ribulose-1,5-bisphosphate carboxylase/oxygenase
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    Topics: Biology
    Notes: Abstract The gene (rbcL) for the large subunit (LSU) of Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) from Cyanophora paradoxa was cloned and the nucleotide sequence determined. Sequence homologies to rbcL genes from other sources clearly indicated a close phylogenetic relationship between the photosynthetic organelles of Cyanophora (cyanelles), green chloroplasts and cyanobacteria. Our data support the hypothesis that the cyanelles of Cyanophora may represent a closely related, but independent, side line to chloroplast evolution. Cyanelles and rhodoplasts or phaeoplasts seem not to be related.
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    Protoplasma 153 (1990), S. 178-185 
    ISSN: 1615-6102
    Keywords: Cryptophyceae ; Dinoflagellate ; Dinophyceae ; Endosymbiosis ; Gymnodinium ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The freshwater dinoflagellateGymnodinium acidotum is known to harbor a cryptomonad endosymbiont whose chloroplasts give the organism its blue-green coloration. Every cell examined from a wild population possessed chloroplasts, mitochondria, and other organelles which are of endosymbiotic origin. Transmission electron microscopy and fluorescence microscopy revealed that only 33% of these cells possessed the nucleus of the endosymbiont. The lack of a cryptomonad nucleus in some cells did not appear to affect the cells' ability to photosynthesize or move in response to varying levels of illumination. This represents the first report of a host/endosymbiont relationship in which a significant number of individuals from a given population lack a major endosymbiont organelle.
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  • 24
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    Molecular genetics and genomics 222 (1990), S. 425-430 
    ISSN: 1617-4623
    Keywords: Endosymbiosis ; Plastid evolution ; Ribulose-1,5-bisphosphate carboxylase ; Rhodophyta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The genes for both subunits of ribulose-1,5-bisphosphate-carboxylase/oxygenase (Rubisco) were located on the plastid DNA (ptDNA) of the unicellular red algaCyanidium caldarium. Both genes are organized together in an operon. The sequence homology of both genes to the corresponding genes from the unicellular red algaPorphyridium aerugineum is remarkably high, whereas homology to Rubisco genes from chloroplasts and two recent cyanobacteria is significantly lower. These data provide strong evidence for a polyphyletic origin of chloroplasts and rhodoplasts. In addition the genes for the small subunit of Rubisco (rbcS) from red algae show about 60% homology torbcS genes from cryptophytes and chromophytes. Thus, homologies in therbcS gene indicate a close phylogenetic relationship between rhodoplasts and the plastids of Chromophyta.
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  • 25
    ISSN: 1432-1432
    Keywords: Rhodoplast ; Chloroplast ; Plastid ; Endosymbiosis ; 5S ribosomal RNA ; Nucleotide sequence ; Secondary structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The 5S ribosomal RNA sequences have been determined for the rhodoplast of the red algaPorphyra umbilicalis and the chloroplast of the coniferJuniperus media. The 5S RNA sequence of theVicia faba chloroplast is corrected with respect to a previous report. A survey of the known sequences and secondary structures of 5S RNAs from plastids and cyanobacteria shows a close structural similarity between all 5S RNAs from land plant chloroplasts. The algal plastid 5S RNAs on the other hand show much more structural diversity and have certain structural features in common with bacterial 5S RNAs. A dendrogram constructed from the aligned sequences by a clustering algorithm points to a common ancestor for the present-living cyanobacteria and the land plant plastids. However, the algal plastids branch off at an early stage within the plastid-cyanobacteria cluster, before the divergence between cyanobacteria and land plant chloroplasts. This evolutionary picture points to the occurrence of multiple endosymbiotic events, with the ancestors of the present algal plastids already established as photosynthetic endosymbionts at a time when the ancestors of the present land plant chloroplasts were still free-living cells.
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  • 26
    ISSN: 1432-072X
    Keywords: Ciliate culture ; Endosymbiosis ; Methanobacterium formicicum ; Methanogenic bacteria ; Plagiopyla nasuta Stein ; Sapropelic protozoa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sapropelic ciliate Plagiopyla nasuta was isolated and cultured in monoculture. Optimal conditions for growth were: 15–20°C, pH about 7, and about 2% of oxygen in the headspace. Cultures of P. nasuta produced methane. Epifluorescence microscopy revealed the presence of methanogenic bacteria as endosymbionts. An endosymbiont of the ciliate was isolated and identified as Methanobacterium formicicum. In the ciliate cell these methanogens were found to be closely associated with microbody-like organelles. No mitochondria could be detected.
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  • 27
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    Archives of microbiology 150 (1988), S. 244-248 
    ISSN: 1432-072X
    Keywords: Origin of plastids ; Endosymbiosis ; Chrysophytes (Ochromonas danica) ; Heliobacterium chlorum ; 16S rRNA oligonucleotide cataloguing ; Reverse transcriptase sequencing ; Phylogenetic relations (Molecular phylogeny) ; Chloroplast evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phylogenetic position of the golden-yellow alga Ochromonas danica chrysoplast was investigated by comparison of the 16S rRNA catalogue and two long 16S rRNA stretches (804 and 454 bases) with catalogues from eubacteria and chloroplasts and with homologoes 16S rRNA regions from Escherichia coli, Bacillus subtilis, Heliobacterium chlorum, Anacystis nidulans and chloroplasts from Zea mays, Nicotiana tabacum, Euglena gracilis and Chlamydomonas reinhardii, respectively. Both approaches indicate a closer relationship of the chrysoplast to chloroplasts and cyanobacteria than to the brownish photoheterotrophic Heliobacterium chlorum for which a common ancestry has recently been hypothesized.
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  • 28
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    Archives of microbiology 149 (1987), S. 4-11 
    ISSN: 1432-072X
    Keywords: Sapropelic ciliates ; T. compressum ; Anaerobiosis ; Endosymbiosis ; Methanogenic bacteria ; Monoxenic culture ; Sterols ; Bacteroides sp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sapropelic ciliates from anoxic mud samples were enriched and cultivated in monoculture together with natural food bacteria growing on cellulose. The ciliates lacked cytochrome oxidase and contained bluish fluorescent endosymbionts. One of the anaerobic ciliates, Trimyema compressum, contained methanogenic bacteria as was shown by methane formation. During continued cultivation, T. compressum gradually lost its endosymbionts. With SEM microscopy no episymbiotic bacteria could be detected. From enrichment cultures of T. compressum, anaerobic bacteria were isolated in pure culture. One of the strains, a Bacteroides spec., proved capable of serving as food bacteria, thus allowing establishment of monoxenic T. compressum cultures. These cultures exhibited a requirement for sterols as growth factors. The doubling time of this ciliate was 13 h at 28°C. The highest yield obtained was 2100 cells/ml.
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  • 29
    ISSN: 1432-072X
    Keywords: Ciliate culture ; Endosymbiosis ; Interspecies hydrogen transfer ; Hydrogenosome ; Methanogenic bacteria ; Methanoplanus endosymbiosus sp. nov. ; Metopus contortus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Epifluorescence microscopy revealed the presence of a methanogenic bacterium as an endosymbiont in the sapropelic marine ciliate Metopus contortus. The in situ methanogenic activity of the symbiont could be demonstrated. The isolated endosymbiont was an irregular, disc-shaped bacterium with a diameter of 1.6–3.4 μm. It had a generation time of 7 or 12 hours on growth on H2/CO2 or formate, respectively. The temperature range for growth was between 16 and 36°C with an optimum at 32°C. The optimal pH range for growth was 6.8 to 7.3. Salts, with an optimum concentration of 0.25 M, and tungsten were required for growth. The mol% G+C was 38.7%. The cell envelope consisted of proteins and a glycoprotein with an apparent molecular weight of 110,000. Morphology, antigenic relationship and the G+C content established the isolate MC1 as a new species of the genus Methanoplanus, and the name Methanoplanus endosymbiosus is proposed.
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    Protoplasma 135 (1986), S. 71-79 
    ISSN: 1615-6102
    Keywords: Dinoflagellate ; Dinophyceae ; Endosymbiosis ; Pyrrophyta ; Woloszynskia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chloroplasts of the freshwater dinoflagellate,Woloszynskia pascheri, were found to contain small, double membrane-bound bodies that appear to be modified bacteria existing in this organelle as endosymbionts. These “chloroplast endosymbionts” (CESs) contain thin filaments, which observations on thin-sectioned and Feulgen-stained material indicate to be strands of “naked” DNA. They also possess putative prokaryotic-sized ribosomes. The outer of the two membranes that surround a CES may be expanded to form cisternae or tubules, which frequently connect with the outer membrane of adjacent CESs. Considering their appearance in relation to free-living bacteria, and their apparently benign presence in the dinoflagellate host, it is suggested that the CESs have been involved in a symbiotic relationship withW. pascheri for some time.
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  • 31
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    Journal of molecular evolution 22 (1985), S. 243-251 
    ISSN: 1432-1432
    Keywords: Molecular archaeology ; Intron evolution ; Mitochondria ; Gene transfer ; Endosymbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We develop a stepwise model for the net transfer of nucleic acid sequences between nonhomologous genomes. This model is then used to explain the two major patterns in the evolutionary history of mitochondrial genomes: the gross reduction of the number of genes, and the subsequent acquisition of introns.
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    Journal of molecular evolution 21 (1984), S. 54-57 
    ISSN: 1432-1432
    Keywords: Mitochondrion ; Cytochrome C ; Rhodospirillaceae ; Endosymbiosis ; rRNA ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The comparative morphology and pigmentation of protists suggest that those with tubular mitochondrial cristae belong to a different lineage than those with lamellar cristae and that the evolutionary divergence might have been very early. We propose that the difference in cristal morphology is the result of separate origins of the mitochondria from endosymbionts related to the Rhodospirillaceae (purple nonsulfur bacteria) but differing in the morphology of their internal membranes. Comparisons of the cytochromes c of protists and the Rhodospirillaceae and of 16s rRNA T1 oligonucleotide catalogs in the Rhodospirillaceae do not contradict, and in fact provide support for, the idea. More extensive evidence may be lacking simply because cytochromes c have been studied in very few protists with tubular mitochondrial cristae.
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  • 33
    ISSN: 1432-072X
    Keywords: Endosymbiosis ; Hydrogenosome ; Methanobacterium formicicum ; Methanogenic bacteria ; Metopus striatus ; Sapropelic protozoa
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    Topics: Biology
    Notes: Abstract The Gram-positive methanogenic endosymbiont of the sapropelic ciliateMetopus striatus was isolated and identified asMethanobacterium formicicum. In the ciliate cell the methanogens are in close association with microbody-like organelles. No mitochondria could be detected. The nature of the microbodies and the physiological background of the observed association are discussed.
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  • 34
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    Archives of microbiology 136 (1983), S. 89-95 
    ISSN: 1432-072X
    Keywords: Coenzyme F420 ; Compound F342 ; Endosymbiosis ; Interspecies H2-transfer ; Methane production ; Methanogenic bacteria ; Metopus striatus ; Pelomyxa palustris ; Sapropelic protozoa-Urkaryotes
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Fluorescent bacteria were demonstrated to be abundantly spread as single cells throughout the cytoplasm of the giant amoeba Pelomyxa palustris, the sapropelic ciliate Metopus striatus and six other anaerobic protozoa examined. The endosymbionts of P. palustris and M. striatus were identified as methanogenic bacteria on the basis of the presence of the deazaflavin coenzyme F420 and the pterin compound F342. Moreover individuals of P. palustris produced methane over a long period of incubation. The number of methanogenic bacteria was above 1010 cells/ml protozoal cytoplasm. Two types of methanogenic bacteria together with unidentified thick bacteria were found in P. palustris. The physiological background of this endosymbiosis and its functioning in degradation processes in the anoxic environment are discussed.
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  • 35
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    Journal of molecular evolution 18 (1982), S. 287-292 
    ISSN: 1432-1432
    Keywords: Evolution ; Endosymbiosis ; Gene transfer ; Transmembrane movement of proteins ; Receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the origin of the mitochondrion and plastid, gene transfer from the ancestral endosymbiont to the host was proposed to be a crucial event. For this genic integration to proceed, products of transferred genes had to return to and enter the endosymbionts. The limiting event was the crossing of the barrier presented by the two semipermeable membranes bounding the proto-organelle. In this paper it is suggested that spontaneous transport allowed transferred gene encoded proteins to enter the endosymbionts before receptors evolved. The effects of these events, including the degeneration of the endosymbiont genome, are discussed. Although the presumed gene transfer had profound effects on the metabolic relationships between host and endosymbionts it probably cannot account for all examples of organelle/cytoplasmic isozyme pairs or the absence of amino acid synthetic enzymes in animal cells.
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  • 36
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    Planta 156 (1982), S. 70-77 
    ISSN: 1432-2048
    Keywords: Cyanelles ; Cyanobacteria ; Cyanophora ; Endosymbiosis ; Nitrate assimilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The taxonomic affinity of Cyanophora paradoxa and its endosymbiotically living cyanelles has not yet been resolved. In the present communication, the enzymes of assimilatory nitrate reduction are investigated in cell-free preparations from the cyanelles and from the eukaryotic host. Nitrate reductase of Cyanophora is a NADH-dependent, soluble enzyme, occurring only in the protoplasm of the eukaryotic host. In contrast, nitrite reductase is ferredoxin-dependent and bound to the thylakoids of cyanelles. Glutamine synthetase and ferredoxin-dependent glutamate synthase (GOGAT) are present both in cyanelles and the eukaryote. Activity levels of alanine dehydrogenase and glutamic acid dehydrogenase are marginal in Cyanopnora, indicating that ammonia is suggest assimilated by the glutamine synthetase GOGAT pathway. The data also that NH 4 + leaves the cyanelles to meet the nitrogen requirements of the eukaryote. It is concluded that the pathway of assimilatory nitrate reduction is similar in Cyanophora and photosynthetic eukaryotic cells and is different from that in byanobacteria.
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    Planta 156 (1982), S. 78-83 
    ISSN: 1432-2048
    Keywords: Cyanelles ; Cyanobacteria ; Cyanophora ; Endosymbiosis ; Photosynthesis (Cyanophora) ; Respiration (Cyanophora)
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Isolated cyanelles of Cyanophora paradoxa perform photosystem I and II dependent Hill reactions. The photosynthetic electron transport of the cyanelles does not show special features uncommon in cyanobacteria or chloroplasts of red algae. A preparation of cyanelles performs photosynthetic O2-evolution with approximately 1/3 of the rate of intact Cyanophora, in only, however, the first three minutes of the experiment. All attempts to stabilize the CO2-fixation activity of isolated cyanelles failed. Isolated cyanelles do not perform KCN-sensitive O2-uptake, indicating that respiratory cytochrome oxidase is lacking in cyanelles. O2-consumption by crude extracts from Cyanophora is inhibited by KCN when N-tetramethyl-p-phenylenediamine/ascorbate or NADH but not NADPH are supplied as the electron donors in contrast to the situation in cyanobacteria. These findings suggest that cyanelles do not respire. It is concluded that cyanelles are not so much related to cyanobacteria as formerly believed, but share many properties with chloroplasts of eukaryotic cells.
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  • 38
    ISSN: 1432-2048
    Keywords: Chlorella ; Endosymbiosis ; Infection ; Paramecium bursaria ; Photobehaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The endosymbiotic unit of Paramecium bursaria and Chlorella spec. shows two types of photobehaviour: 1) A step-up photophobic response which possibly depends on photosensitive agents in the ciliate cell itself — as is also shown by alga-free Paramecium bursaria - and can be drastically enhanced by photosynthetic activity of symbiotic algae; and 2) a step-down photophobic response. The step-down response leads to photoaccumulation of green paramecia. Both types of photobehaviour in Paramecium bursaria do not depend on any special kind of algal partners: The infection of alga-free Paramecium bursaria with different Chlorella species results in new ciliatealgae-associations. They are formed not only by combination of the original symbiotic algae with their host, but also by infection with other symbiotic or free-living (aposymbiotic) chlorellae, respecitively. Systems with other than the original algae are not permanently stable — algae are lost under stress conditions — but show the same types of photobehaviour. Photoaccumulation in general requires algal photosynthesis and occurs only with ciliates containing more than fifty algae/cell. It is not mediated by a chemotactic response to oxygen in the medium, since it occurs at light fluence rates not sufficient for a release of oxygen by the symbiotic system, e.g., below its photosynthetic compensation point. Photoresponses can be inhibited by 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU). Sensory transduction does not depend on any special symbiotic features of the algae, e.g., sugar excretion. The participation of oxygen in the Paramecium cell, of its cytoplasmic pH and of ions released or taken up by endosymbiotic algae in sensory transduction is discussed.
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  • 39
    ISSN: 1432-2048
    Keywords: Cyanobacteria ; Cyanocyta ; Cyanophora ; Endosymbiosis ; Regulation (development)
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    Notes: Abstract The prokaryote Cyanocyta korschikoffiana was isolated from the eukaryote Cyanophora paradoxa. The synthesis of several thylakoid proteins in these cyanelles is influenced by light and darkness and is sensitive to cycloheximide, the inhibitor of the eukaryotic host's translation. The possibility of a direct coordination between the translations of the host and of the cyanelles is discussed.
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  • 40
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    Journal of molecular evolution 17 (1981), S. 133-139 
    ISSN: 1432-1432
    Keywords: Endosymbiosis ; Cell evolution ; Isozymes ; Plant biochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The hypothesis stating that chloroplasts were derived from a photosynthetic procaryote is explored at a genetic and biochemical level. A transfer of genetic material from the endosymbiont to the nucleus of the host cell is proposed along with a corollary argument that the protein products of such transferred genes have remained specific to the chloroplast. This model provides an explanation for the presence of plastid-specific isozymes which are coded by nuclear DNA. It also suggests that the genome of the endosymbiont contributed the information necessary for the biosynthesis of carotenoids and the “essential” amino acids and the assimilation of nitrate-nitrogen and sulfate-sulfur. Animal cells lack these capabilities not because such were lost subsequent to the divergence of the plant and animal lines, but because animal cells did not become host to the appropriate symbionts. Additional implications of this thesis are discussed.
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  • 41
    ISSN: 1432-072X
    Keywords: Paramecium bursaria ; Chlorella sp. ; Symbiosis ; Endosymbiosis ; Ribulose 1,5-bisphosphate carboxylase ; Carbonic anhydrase
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The activities of ribulose 1,5-bisphosphate carboxylase and of carbonic anhydrase were studied in cell-free extracts of two symbiotic Chlorella strains isolated from Paramecium bursaria and from Spongilla sp., and of two nonsymbiotic strains of Chlorella (Chlorella fusca and Chlorella vulgaris) cultivated at varied CO2-concentrations. The symbiotic Chlorella of Paramecium bursaria differs distinctly from the other Chlorella strains by a higher activity of ribulose 1,5-bisphosphate carboxylase, which is independent of the actual CO2-concentration, and by a lack of carbonic anhydrase activity. These properties are discussed with respect to their ecological significance.
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  • 42
    ISSN: 1432-2048
    Keywords: Chlorella ; Endosymbiosis ; Maltose biosynthesis ; Paramecium bursaria
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    Notes: Abstract The endosymbiotic Chlorella sp. from Paramecium bursaria excretes maltose both in the light and in the dark. Experiments on photosynthetic 14CO2 fixation and 14CO2 pulse-chase experiments show that maltose is synthesized in the light directly from compounds of the Calvin cycle, whereas in the dark it results from starch degradation.
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  • 43
    ISSN: 1432-2048
    Keywords: Chlorella ; Endosymbiosis ; Paramecium bursaria ; Photoaccumulation ; Photoreceptor ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The endosymbiotic unit of Paramecium bursaria with Chlorella sp. photoaccumulates in white, blue-green, and red light (λ〈700 nm), whereas alga-free Paramecia never do. The intensity of photoaccumulation depends on both the light fluence rate and the size of the symbiotic algal population. Photoaccumulation can be stopped completely with 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosynthetic electron transport. Hence the photosynthetic pigments of the algae act as receptors of the light stimulus for photomovement and a close connection must exist between photosynthesis of the algae and ciliary beating of the Paramecium.
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  • 44
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    Journal of molecular evolution 10 (1977), S. 1-6 
    ISSN: 1432-1432
    Keywords: Evolution ; Ribosomes ; Genotype-Phenotype ; Cytoplasm ; Endosymbiosis ; Procaryote ; Eucaryote ; Progenote
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A central evolutionary question is whether the eucaryotic cytoplasm represents a line of descent that is separate from the typical bacterial line. It is argued on the basis of differences between their respective translation mechanisms that the two lines do represent separate phylogenetic trees in the sense that each line of descent independently evolved to a level of organization that could be called procaryotic. The two lines of descent, nevertheless shared a common ancestor, that was far simpler than the procaryote. This primitive entity is called a progenote, to recognize the possibility that it had not yet completed evolving the link between genotype and phenotype. This concept changes considerably the view one takes toward cellular evolution.
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    Journal of molecular evolution 10 (1977), S. 93-96 
    ISSN: 1432-1432
    Keywords: Evolution ; Endosymbiosis ; Mitochondrion ; Photosynthetic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The possibility is put forth that the mitochondrion did not originate from an endosymbiosis, 1–2 billion years ago, involving an aerobic bacterium. Rather, it arose by endosymbiosis in a much early, anaerobic period, and was initially a photosynthetic organelle, analogous to the modern chloroplast. This suggestion arises from a reconsideration of the nature of endosymbiosis. It ex-plains the remarkable diversity in mitochondrial information storage and processing systems.
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