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  • 1
    Electronic Resource
    Electronic Resource
    Phage and defective phage of strains of Myxococcus (1976)
    Springer
    Archives of microbiology 108 (1976), S. 271-279 
    Details
    ISSN: 1432-072X
    Keywords: Bacteriophage ; Myxococcus ; DNA ; Restriction ; Phage proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. Phage-like particles were found in the supernatants of cultures of strains of Myxococcus xanthus, M. virescens and M. fulvus. The largest number of such particles was associated with M. virescens V2. Most of the particles were similar in morphology to the virulent Myxococcus phage, MX-1. 2. Several new phages were isolated from soil and animal droppings. A new phage was isolated from cultures of M. virescens V2. All resembled phage MX-1 in morphology and were related to phage MX-1 serologically. One of these phage, øm, was characterized by fractionation of its proteins by SDS-polyacrylamide gel electrophoresis and by analysis of the restriction fragments of its DNA. The very close relatedness with MX-1 was confirmed by these techniques. Phage øm, was found to exist in a state of pseudolysogeny with strains of M. virescens and M. fulvus. 3. Two types of bacteriocin-like activity were found associated with Myxococcus strains. In one case, the activity was extracted from chloroform-killed or from sonicated cells. In the second case it was associated with extracellular material. Strains of Salmonella and Cytophaga were found to be good indicators for this latter activity. These strains were found to be killed by phage MX-1. 4. The significance of these data for origin of the phages of myxococci are discussed and it is proposed that MX-1 and the newly isolated phages may be virulent mutants of a family of lysogenic phages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00454852
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  • 2
    Electronic Resource
    Electronic Resource
    DNA of Myxococcus bacteriophage MX-1: Macromolecular properties and restriction fragments (1976)
    Springer
    Archives of microbiology 108 (1976), S. 221-226 
    Details
    ISSN: 1432-072X
    Keywords: Bacteriophage MX-1 ; Myxococcus ; DNA ; Restriction fragments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. Bacteriophage MX-1 is a virulent DNA phage whose hosts include strains of Myxococcus xanthus, M. fulvus and M. virescens. DNA was extracted from purified phage preparations. The molecular weight of phage DNA was measured by sedimentation-velocity and by rate-zonal ultracentrifugation. The apparent molecular weight was found to vary for reasons discussed in the text. From ratezonal ultracentrifugation, using calibrated sucrose gradients, the molecular weight was calculated to be 149 (± 22)×106 daltons. The base composition of the DNA was estimated by different methods and was found to be 50–52% (G+C). The DNA demonstrated an anomalous thermal denaturation profile in dilute buffer. Denatured DNA was fractionated by ion-exchange chromatography and by buoyant-density centrifugation. No significant strand separation was obtained and it was concluded that overall base compositions of the two strands are very similar. 2. DNA from bacteriophage MX-1 was hydrolysed with restriction endonucleases R. EcoRI, R. EcoRII and R. HindIII. The restriction fragments were catalogued and their apparent molecular weights calculated from electrophoresis gels calibrated with fragments from the DNA of coliphage λ. From the total fragments obtained with nuclease R. EcoRI, the minimum apparent molecular weight of MX-1 DNA was found to be 130×106 daltons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428955
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  • 3
    Electronic Resource
    Electronic Resource
    An embryogenic cell line of maize from A188 (Minnesota) contains Mu1-like elements (1988)
    Springer
    Plant molecular biology 10 (1988), S. 273-279 
    Details
    ISSN: 1573-5028
    Keywords: embryogenic cell culture ; maize ; Mutator ; transposable elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The maize inbred line A188 is popularly used for the production of embryogenic cell lines. A188, maintained at the University of Minnesota, was found upon molecular analysis to contain 2 to 4 copies of a DNA sequence very similar in structure to transposable Mu1 elements, which have been implicated in Robertson's Mutator system. These Mu1-like elements are in the same chromosomal locations in sibling plants and in A188 cell cultures derived from them. This suggests that the elements are in an inactive state and do not undergo transposition. However, we have observed that they are not modified at the target sites for certain restriction endonucleases. Possible causes for the apparent lack of transposition of these Mu1-like elements in these A188 lines are discussed. Inasmuch as the elements do not transpose, they must be maintained in this line as homozygous Mendelian elements by self-pollination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027404
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  • 4
    Electronic Resource
    Electronic Resource
    Concomitant regulation of Mu1 transposition and Mutator activity in maize (1987)
    Springer
    Molecular genetics and genomics 208 (1987), S. 57-62 
    Details
    ISSN: 1617-4623
    Keywords: Transposable elements ; Mutation ; Mutator ; Maize
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mutagenic activity of the maize transposable element system Mutator can be lost by outcrossing to standard, non-Mutator lines or by repetitive intercrossing of genetically diverse Mutator lines. Lines losing Mutator mutagenic activity in either manner retain high copy numbers (10–15 per diploid genome) of the Mutator-associated Mu transposable elements. Frequent transposition of Mu1-related elements is observed only in active Mutator lines, however. The loss of Mutator activity on intercrossing is correlated with an increase in the copy number of Mu1-like elements to 40–50 per diploid genome, implying a self-encoded or self-activated negative regulator of Mu1 transposition. The outcross loss of Mutator activity is only weakly correlated with a low Mu element copy number and may be due to the loss of a positive regulatory factor encoded by a subset of Mu1-like elements. Transposition of Mu elements in active Mutator lines generates multiple new genomic positions for about half the elements each plant generation. The appearance of Mu1-like elements in these new positions is not accompanied by equally high germinal reversion frequencies, suggesting that Mu1 may commonly transpose via a DNA replicative process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330422
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  • 5
    Electronic Resource
    Electronic Resource
    Stimulation of acid invertase activity by indol-3yl-acetic acid in tissues undergoing cell expansion (1986)
    Springer
    Plant growth regulation 4 (1986), S. 259-271 
    Details
    ISSN: 1573-5087
    Keywords: Acid invertase (β-fructofuranosidase) ; auxin ; cell expansion ; Phaseolus vulgaris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The soluble acid invertase activity of young, excised P. vulgaris internodal segments fell when they were incubated in water, and their elongation ceased within 6–7 h. IAA (10 μM) promoted segment elongation and stimulated an increase in the specific activity of acid invertase to a level greater than that originally present. The rate of segment elongation in the presence of IAA was closely and positively correlated with the specific activity of the enzyme. Optimum concentration of IAA for both elongation and stimulation of invertase activity was 10 μM. Concurrent protein synthesis was necessary for these responses to IAA. Segments cut from mature, fully-elongated internodes did not responsd to IAA. Inclusion of Ca2+, vanadate or mannitol in the incubation medium abolished IAA-induced segment elongation but did not inhibit the stimulation of acid invertase activity by IAA. Auxin-induced elongation and acid invertase activity were both substantially increased in the presence of up to 25 mM D-glucose or up to 50 mM sucrose. Inclusion of either sugar in the medium considerably increased tissue hexose concentrations. Under some circumstances cell growth and invertase synthesis may compete for available hexose substrate. It is concluded that IAA-induced promotion of acid invertase in P. vulgaris internodal segments is not simply an indirect consequence of removal of end-product (hexose) during IAA-induced cell growth and that a more direct action of IAA on enzyme turnover is involved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028169
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  • 6
    Electronic Resource
    Electronic Resource
    Invertase activity in sinks undergoing cell expansion (1984)
    Springer
    Plant growth regulation 2 (1984), S. 327-337 
    Details
    ISSN: 1573-5087
    Keywords: β-D-fructofuranoside fructohydrolase ; acid invertase ; cell expansion ; carbohydrate metabolism ; sinks ; plant growth regulators
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract During the development of roots, internodes and leaves, closely correlated changes occur in the rates of cell expansion, specific activities of acid invertase and concentrations of hexose sugars and sucrose. Rates of cell growth and acid invertase activities frequently exhibit closely coupled responses to environmental changes and to growth regulator treatments. The possibility is considered that, by controlling the availability of hexose substrates for cellular metabolism, acid invertase may regulate cell growth. Potential mechanisms regulating the in vivo activity of acid invertases are reviewed and attention is drawn to the need for more information on the sub-cellular localization of the enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027292
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