1887

Abstract

SUMMARY: When a culture of the temperature-sensitive DNA mutant tsSI is irradiated with a sublethal dose of ultraviolet or ionizing radiation and is plated immediately, all the bacteria give rise, after 36 h incubation, to colonies identical to those derived from unirradiated bacteria. However, when the irradiated population is held at its restrictive temperature (39 °C) (restrictive temperature holding) for 3 h before being plated, less than 0·1% of the surviving bacteria give rise to normal colonies, the rest producing, after incubation for 96 h, small malformed colonies. Qualitatively, the same effect is observed when u.v.-irradiated wild-type is incubated at 39 °C in the presence of nalidixic acid before plating. Compared with the loss of viability, the loss of normal colony development as a function of the radiation dose is sensitive, having I/e values of 210 ergs/mm for u.v. radiation and of 4 to 5 krad for Co -radiation. These are identical to the radiation dose-response values of a recombination-deficient mutant of At first the abnormal colonies consist entirely of giant bacteria but eventually a few bacteria with normal morphology appear and because of their much faster generation time a highly sectored colony results. These colonies can be ‘rescued’ by plating the irradiated bacteria held at 39 °C on agar containing pantoyl lactone, their growth being identical to that of unirradiated bacteria. Abnormal colony development is not a general phenomenon in temperature-sensitive mutants of but occurs in those mutants which are sensitized to radiation when held at 39 °C. It is concluded that these abnormal colonies are produced as a result of a defect in a recombination function and that this function is also involved in the regulation of normal cell division.

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/content/journal/micro/10.1099/00221287-86-2-343
1975-02-01
2024-03-28
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References

  1. Adler H. I., Hardigree A. A. 1964; Analysis of a gene controlling cell division and sensitivity to radiation in Escherichia coli. Journal of Bacteriology 87:720–726
    [Google Scholar]
  2. Anderson A. W., Nordan H. C., Cain R. F., Parrish G., Duggan D. 1956; Studies on a radio resistant micrococcus. Isolation, morphology, cultural characteristics, and resistance to gamma radiation. Food Technology 10:575–578
    [Google Scholar]
  3. Boling M. E., Setlow J. K. 1966; The resistance of Micrococcus radiodurans to ultraviolet radiation. III. A repair mechanism. Biochimica et biophysica acta 123:26–33
    [Google Scholar]
  4. Driedger A. A. 1970; The ordered growth pattern of microcolonies of Micrococcus radiodurans; firstgeneration sectoring of induced lethal mutations. Canadian Journal of Microbiology 16:1133–1135
    [Google Scholar]
  5. Driedger A. A., Grayston M. J. 1971; The effects of nalidixic acid on X-ray induced DNA degradation and repair in Micrococcus radiodurans. Canadian Journal of Microbiology 17:501–505
    [Google Scholar]
  6. Duggan D. E., Anderson A. W., Elliker P. R., Cain R. F. 1959; Ultraviolet exposure studies on a gamma radiation resistant micrococcus isolated from food. Food Research 24:376–382
    [Google Scholar]
  7. Green M. H. L., Greenberg J., Donch J. 1969; Effect of a recA gene on cell division and capsular polysaccharide production in a lon strain of Escherichia coli. Genetical Research 14:159–162
    [Google Scholar]
  8. Howarij-Flanders P., Simson F., Theriot L. 1964; A locus that controls filament formation and sensitivity to radiation in Escherichia coli K-12. Genetics 49:237–246
    [Google Scholar]
  9. Howard-Flanders P., Theriot L., Stedeford J. B. 1969; Some properties of excision-defective recombination-deficient mutants of Escherichia coli KI2. Journal of Bacteriology 97:1134–1141
    [Google Scholar]
  10. Inouye M. 1971; Pleiotropic effect of the rec A gene of Escherichia coli: uncoupling of cell division from deoxyribonucleic acid replication. Journal of Bacteriology 106:539–542
    [Google Scholar]
  11. Moseley B. E. B. 1963; The variation in X-ray resistance of Micrococcus radiodurans and some of its less pigmented mutants. International Journal of Radiation Biology 6:489
    [Google Scholar]
  12. Moseley B. E. B. 1967; The isolation and some properties of radiation-sensitive mutants of Micrococcus radiodurans. Journal of General Microbiology 49:293–300
    [Google Scholar]
  13. Moseley B. E. B., Mattingly A., Copland H. J. R. 1972a; Sensitization to radiation by loss of recombination ability in a temperature-sensitive DNA mutant of Micrococcus radiodurans held at its restrictive temperature. Journal of General Microbiology 72:329–338
    [Google Scholar]
  14. Moseley B. E. B., Mattingly A., Shimmin A. 1972b; Isolation and some properties of temperature-sensitive mutants of Micrococcus radiodurans defective in DNA synthesis. Journal of General Microbiology 70:399–409
    [Google Scholar]
  15. Rupp W. D., Howard-Flanders P. 1968; Discontinuities in the DNA synthesized in an excision defective strain of Escherichia coli following ultraviolet irradiation. Journal of Molecular Biology 31:291–304
    [Google Scholar]
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