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  • 1975-1979  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 108 (1976), S. 227-230 
    ISSN: 1432-072X
    Keywords: Bacteriophage MX-1 ; Myxococcus virescens ; Myxococcus xanthus ; Restriction ; Modification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The plating efficiency of bacteriophage MX-1 on Myxococcus xanthus strains A and B and M. virescens V2 were compared. Comparison of strains V2 and A suggest that V2 is restrictive and A is not (restriction coefficient was approximately 8). A derivative of M. virescens V2 (strain V2-9) was obtained by repeated exposure of strain V2 to ultraviolet radiation. Strain V2-9 was also unrestrictive. Strain B is apparently unrestrictive too but analysis of phenotypic changes in phage derived from hosts V2, B and A suggested that some of the host-cell processes differ from orthodox restriction and modification. 2. Cell-free extracts from M. virescens V2 were fractionated by ion-exchange chromatography and two restriction endonucleases, R. MviV2I and R. MviV2II were identified. Nuclease I was found to hydrolyse coliphage λ DNA at apparently one site only and MX-1 DNA at approximately 10 sites; nuclease II was found to hydrolyse MX-1 DNA at a very large number of sites and its restriction sequence was of comparable frequency with that of R. EcoRII. “Modified MX-1 DNA”, obtained from phage whose last host was M. virescens V2 was hydrolysed by nuclease II but not by nuclease I. The significance of these findings for restriction in myxococci is discussed.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 108 (1976), S. 271-279 
    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.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 108 (1976), S. 221-226 
    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.
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  • 4
    Publication Date: 1976-01-01
    Print ISSN: 0302-8933
    Electronic ISSN: 1432-072X
    Topics: Biology
    Published by Springer
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  • 5
    Publication Date: 1976-01-01
    Print ISSN: 0302-8933
    Electronic ISSN: 1432-072X
    Topics: Biology
    Published by Springer
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  • 6
    Publication Date: 1976-01-01
    Print ISSN: 0302-8933
    Electronic ISSN: 1432-072X
    Topics: Biology
    Published by Springer
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