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  • 1
    ISSN: 1432-0983
    Keywords: Aspergillus ; Mitochondrial DNA ; Interspecies recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mitochondrial genome of Aspergillus nidulans var. echinulatus is approximately 20% larger than that of the closely related species Aspergillus nidulans (Eidam) Winter. Restriction enzyme mapping and electron microscopy has revealed that the size difference is due to the presence of six inserted sequences in the former. With the exception of a small number of species specific restriction sites and the six insertions/deletions, the two mitochondrial genomes appear identical. Protoplast fusion between the two species followed by selection of extranuclear drug resistance markers resulted in the isolation of recombinant mitochondrial genomes in an A. nid. var. echinulatus background. Restriction maps of the hybrid genomes indicated that three of the additional sequences found in A. nid. var. echinulatus could be transferred to the A. nidulans nuclear background without loss or detectable alteration. The nature of the additional mitochondrial DNA and high frequency transfer of certain species specific sequences is discussed with reference to studies in yeast and Neurospora crassa.
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  • 2
    ISSN: 1432-072X
    Keywords: Key words Phototrophic bacteria ; Taxonomy ; New ; species ; New genus ; Rhodospira ; Bacteriochlorophyll ; b ; Tetrahydrospirilloxanthin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new phototrophic purple bacterium was isolated from a flat, laminated microbial mat in a salt marsh near Woods Hole, Mass., USA. The spiral-shaped bacterium was highly motile and had bipolar tufts of flagella and intracytoplasmic membranes of the vesicular type. The major photosynthetic pigments were identified as the carotenoid tetrahydrospirilloxanthin and bacteriochlorophyll b. The long wavelength in vivo absorption maximum of the bacteriochlorophyll was at 986 nm. The marine bacterium showed optimal growth in the presence of 2% NaCl. It utilized a number of organic substrates as carbon and energy sources and required vitamins and sulfide as a reduced sulfur source for growth. In the presence of sulfide, elemental sulfur globules were formed outside the cells. Elemental sulfur was not further oxidized to sulfate. The new isolate had a unique lipid and fatty acid composition, and according to the 16S rRNA gene sequence, it is most similar to Rhodospirillum rubrum. It is described as a new species and assigned to a new genus with the proposed name Rhodospira trueperi.
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  • 3
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A detailed map of the 32 kb mitochondrial genome of Aspergillus nidulans has been obtained by locating the cleavage sites for restriction endonucleases Pst I, Bam H I, Hha I, Pvu II, Hpa II and Hae III relative to the previously determined sites for Eco R I, Hind II and Hind III. The genes for the small and large ribosomal subunit RNAs were mapped by gel transfer hybridization of in vitro labelled rRNA to restriction fragments of mitochondrial DNA and its cloned Eco R I fragment E3, and by electron microscopy of RNA/DNA hybrids. The gene for the large rRNA (2.9 kb) is interrupted by a 1.8 kb insert, and the main segment of this gene (2.4 kb) is separated from the small rRNA gene (1.4 kb) by a spacer sequence of 2.8 kb length. This rRNA gene organization is very similar to that of the two-times larger mitochondrial genome of Neurospora crassa, except that in A. nidulans the spacer and intervening sequences are considerably shorter.
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  • 4
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The cpn60 and cpn10 genes from psychrophilic bacterium, Oleispira antarctica RB8, showed a positive effect in Escherichia coli growth at low temperature, shifting its theoretical minimal growth temperature from +7.5°C to −13.7°C [Ferrer, M., Chernikova, T.N., Yakimov, M., Golyshin, P.N., and Timmis, K.N. (2003) Nature Biotechnol 21: 1266–1267]. To provide experimental support for this finding, Cpn60 and 10 were overproduced in E. coli and purified to apparent homogeneity. Recombinant O.Cpn60 was identical to the native protein based on tetradecameric structure, and it dissociates during native PAGE. Gel filtration and native PAGE revealed that, in vivo and in vitro, (O.Cpn60)7 was the active oligomer at 4–10°C, whereas at 〉 10°C, this complex was converted to (O.Cpn60)14. The dissociation reduces the ATP consumption (energy-saving mechanism) and increases the refolding capacity at low temperatures. In order for this transition to occur, we demonstrated that K468 and S471 may play a key role in conforming the more advantageous oligomeric state in O.Cpn60. We have proved this hypothesis by showing that single and double mutations in K468 and S471 for T and G, as in E.GroEL, produced a more stable double-ring oligomer. The optimum temperature for ATPase and chaperone activity for the wild-type chaperonin was 24–28°C and 4–18°C, whereas that for the mutants was 45–55°C and 14–36°C respectively. The temperature inducing unfolding (TM) increased from 45°C to more than 65°C. In contrast, a single ring mutant, O.Cpn60SR, with three amino acid substitutions (E461A, S463A and V464A) was as stable as the wild type but possessed refolding activity below 10°C. Above 10°C, this complex lost refolding capacity to the detriment of the double ring, which was not an efficient chaperone at 4°C as the single ring variant. We demonstrated that expression of O.Cpn60WT and O.Cpn60SR leads to a higher growth of E. coli at 4°C (µmax, 0.22 and 0.36 h−1 respectively), whereas at 10–15°C, only E. coli cells expressing O.Cpn60 or O.Cpn60DR grew better than parental cells (–cpn). These results clearly indicate that the single-to-double ring transition in Oleispira chaperonin is a wild-type mechanism for its thermal acclimation. Although previous studies have also reported single-to-double ring transitions under many circumstances, this is the first clear indication that single-ring chaperonins are necessary to support growth when the temperature falls from 37°C to 4°C.
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  • 5
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The holin function Ejh of the pneumococcal bacteriophage EJ-1 has been characterized. It shows structural features similar to, and functionally complemented, the prototype member of the holin family. In Escherichia coli and Pseudomonas putida the Ejh product caused cellular death, and changes in cell morphology could be accounted for by lesions in the cytoplasmic membrane. Expression of ejh resulted in the inhibition of growth in a variety of phylogenetically distant bacterial genera, suggesting a broad spectrum of action. Concomitant expression of the ejh and ejl (encodes a lysin) genes led to lysis of E. coli and P. putida cells. Remarkably, the Ejl lysin was able to attack murein from bacteria lacking choline in their sacculi, which suggests that pneumococcal lysins have a broader substrate specificity than previously assumed. Furthermore, the Ejh holin was able to trigger activity of the major pneumococcal autolysin cloned and expressed in E. coli, and this raised new questions about the regulation of this model autolysin. A new function for holins in systems where the phage lysin is supposed to be associated with the membrane is proposed.
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  • 6
    ISSN: 1432-0878
    Keywords: Key words Cytochalasin D ; Microtubuli ; Myxobacteria ; Protein kinase C ; Staurosporin ; Cell culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effects of the novel myxobacterial compound rhizopodin on mammalian cells were studied and compared with those of latrunculin B. Both substances induced adherently growing L929 mouse fibroblasts and PtK2 potoroo kidney cells to produce long, narrow, branched extensions or runners. Rhizopodin was more efficient than latrunculin B in that respect (minimal inhibitory concentration with L929 cells 5 nM vs 50 nM), and, in contrast to latrunculin B, its effects were permanent. Rhizopodin-treated cells became much larger than normal cells and were multinucleate, yet stayed alive and biochemically active for several weeks. Latrunculin B-treated cells returned to a quasi-normal state within 3–4 days. But latrunculin B acted faster, with the first effects becoming visible almost immediately upon the addition of the drug, while the first rhizopodin effects were seen 10 min later. Both substances caused reorganization of the actin cytoskeleton. When 100 nM rhizopodin was added to PtK2 cells, the stress fibers began to decay after just 10 min and had disappeared completely after about 3 h. Later there was a gradual restitution of F-actin. Long F-actin fibers were seen within the runners, and only there; in fact, these fibers may be responsible for the development and extension of the runners. The microtubuli network adjusted itself to the new cell morphology, but was not directly impaired by the compound.
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  • 7
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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