1887

Abstract

SUMMARY

Continuous growth of was studied to determine whether the organism was capable of uninterrupted hyphal elongation, whether there was any evidence of homeostatic mechanisms controlling growth over extended periods and, particularly, whether spontaneous mutants with suppressive phenotypes were capable of being expressed. Parallel cultures, A and B, having a common origin, were incapable of uninterrupted growth but permanent cessations of growth were not encountered. The A-culture showed frequent stops of long duration whereas B had infrequent stops of short duration. This stop–start growth behaviour in the A- and B-cultures was determined by two different cytoplasmic factors. Both extra-nuclear mutants show decreased cytochrome-c oxidase activity (Bertrand & Pittenger, unpublished). These stopper phenotypes may be similar to ‘vegetative death’ in Aspergillus and ‘senescence’ in Podospora. Both A- and B-cultures showed several major increases and decreases in rate, in addition to more frequent minor fluctuations. The general constancy of growth, however, and the routine restoration of growth after cessations, as well as following either transient or long-term growth rate decreases, indicated that homeostatic mechanisms were capable of buffering the organisms against most deleterious intracellular effects. Two spontaneous nuclear mutants with decreased growth rates as homokaryons also accumulated during growth. These altered nuclear types, whose growth rates were clearly non-adaptive, nevertheless had selective values. Their proportions increased significantly during growth to the extent of either completely displacing the original type or of reaching a high enough proportion so that growth rates were decreased and the morphology of the cultures altered. These nuclear and extranuclear mutants appeared to have a selective advantage because of suppressive characteristics.

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/content/journal/micro/10.1099/00221287-50-3-337
1968-03-01
2021-08-01
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References

  1. Jinks J. L. 1958; Cytoplasmic differentiation in fungi. Proc. R. Soc. B 148314
    [Google Scholar]
  2. Jinks J. L. 1959; Lethal suppressive cytoplasms in aged clones of Aspergillus glaucus . J. gen. Microbiol 21:397
    [Google Scholar]
  3. Jinks J. L. 1964 Extrachromosomal Inheritance Englewood Cliffs, N.J.: Prentice-Hall;
    [Google Scholar]
  4. Marcou D. 1961; Notion de longévité et nature cytoplasmique du déterminant de la sénescence chez quelques champignons. Annls Sci. nat. (Bot.) series 12653
    [Google Scholar]
  5. McDougall K. J., Pittenger T. H. 1962; Observations of perpetual hyphal propagation in Neurospora. Neurospora News 2:10
    [Google Scholar]
  6. McDougall K. J., Pittenger T. H. 1966; A cytoplasmic variant of Neurospora crassa . Genetics 54:551
    [Google Scholar]
  7. Pittenger T. H., Kimball A. W., Atwood K. C. 1955; Control of nuclear ratios in Neurospora heterokaryons. Am. J. Bot 42:954
    [Google Scholar]
  8. Ryan F. J., Beadle G. W., Tatum E. L. 1943; The tube method of measuring the growth rate of Neurospora. Am. J. Bot 30:784
    [Google Scholar]
  9. Vogel H. J. 1956; A convenient medium for Neurospora (medium N). Microbiol. Genet. Bull 13:42
    [Google Scholar]
  10. Westergaard M., Mitchell H. K. 1947; Neurospora. V. A synthetic medium favouring sexual reproduction. Am. J. Bot 34:573
    [Google Scholar]
  11. Woodward D. O., Munkres K. D. 1966; Alterations in a maternally inherited mitochondrial structural protein in respiratory deficient strains of Neurospora. Proc. Natn. Acad. SciU.S.A 55872
    [Google Scholar]
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