The Journal of General and Applied Microbiology
Online ISSN : 1349-8037
Print ISSN : 0022-1260
ISSN-L : 0022-1260
HEREDITARY VARIATION AND RECOMBINATION IN KOJI-MOLDS (ASPERGILLUS ORYZAE AND ASP. SOJAE)
V. HETEROCARYOSIS
CHIYOKO ISHITANIKIN-ICHIRO SAKAGUCHI
Author information
JOURNAL FREE ACCESS

1956 Volume 2 Issue 4 Pages 345-400

Details
Abstract

1. The frequency of hyphal fusions is strongly affected by various conditions; the main factors have been investigated.
a) The frequency of fusions is proportionate to the density of conidia per unit volume of the medium; the higher frequencies were obtained when conidia were less than 10μ apart.
b) The concentration and the reaction of the media are important factors; optimal concentrations are between 1/5 and 1/20 of the original concentrations, and optimal reactions are between pH 5.4 and 6.0.
c) As concerns the effect of genetic conditions on anastomosis, there was scarcely any difference in the frequency of fusion between the test strain, Asp. oryzae K.B., and different strains of Koji-molds, but there were considerable differences in interspecific and intergeneric crosses. In the Aspergilli, Asp. tamarii, Asp. ochraceus, Asp. wentii, and various black Aspergillus species gave much higher frequencies of anastomosis than other species. In the Penicillia, only the Monoverticillata and some members of the Biverticillata anastomosed with the test strains in comparatively low frequencies.
2. The use of genetic markers (size of conidia, color of conidia, and nutritional requirements) has been examined for their usefulness in the detection of heterocaryons.
a) The large size of conidia produced in multinucleate strains such as Koji-molds proved useful in detecting heterocaryons.
b) The use of conidial color only as a criterion, without genetic confirmation, does not give reliable results.
c) Double nutritional markers give critical evidence for the formation of heterocaryons.
3. Allelism-tests were carried out by using various mimic mutants and the presence of pseudo-allelism was suggested for an arginineless locus. The genetic steps in arginine synthesis were in accordance with those in N. crassa and in P. notatum, but nor in Asp. nidulans; arginine is synthesized from ornithine through citrulline.
4. Heterocaryotic strains are unstable and segregate out into their component strains. The segregation ratios are affected both by genetic back-ground and cultural conditions.
5. The phenotype of heterocaryons between two mutants is generally like that of the wild type, differing from the component strains in both morphology and physiology.
a) The increase of conidial size and nuclear number of in heterocaryons is a remarkable characteristic of the Koji-molds.
b) Heterocaryons obtained by mixed culture in various combinations showed enzyme activities that were weaker than either parent, intermediate between them, or like one or the other.
6. Heterocaryosis was induced by the UV treatment of homo-type strains in Asp. oryzae aX without hyphal fusion.

Content from these authors
© The Microbiology Research Foundation
Next article
feedback
Top