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Variation of colony morphology and chromosomal rearrangement in Candida tropicalis pK233
T Suzuki1, Y Miyamae, I Ishida
1Biological Laboratory, Faculty of Science, Nara Women's University, Japan.
Abstract:
UV irradiation treatment of the asexual yeast Candida tropicalis gave rise to morphological mutants exhibiting at least four different types of abnormal colonies on glucose-containing solid medium. These mutants were named according to their colony morphologies: 'doughnut', 'frilly', 'echinoid' and 'walnut' mutants. The doughnut mutant produced a wrinkled colony with a hollow in its central region that was rich in filamentous pseudohyphal cells. With increased incubation time, the colony gradually changed to a reticulate shape. The parent strain, which normally produced smooth colonies, gave similar colonies to those of the doughnut mutant when grown in medium containing oleic acid as carbon source. Both the frilly and the walnut mutants produced pseudohyphal cells in a similar fashion to the doughnut mutant. The echinoid mutant produced an echinulate colony morphology with aerial hyphae and contained true hyphal cells as well as pseudohyphal ones. Pulsed-field gel electrophoresis showed that the echinoid and frilly mutants had different karyotypes from that of their parent strain, suggesting the occurrence of chromosomal rearrangements associated with these morphological mutations.
Insights
UV irradiation induced morphological mutants in Candida tropicalis yeast, revealing distinct colony forms like doughnut and echinoid. These mutations, particularly in echinoid and frilly types, are linked to chromosomal changes.
Area of Science:
- Mycology
- Yeast genetics
- Cellular morphology
Background:
- Candida tropicalis is an asexual yeast with implications in various biological processes.
- Understanding yeast morphology is crucial for studying cellular development and genetic variation.
- UV irradiation is a known mutagenic agent used to induce genetic alterations in microorganisms.
Purpose of the Study:
- To investigate the morphological changes in Candida tropicalis induced by UV irradiation.
- To characterize the distinct colony morphologies of the resulting mutants.
- To explore potential genetic underpinnings, such as chromosomal rearrangements, of these morphological mutations.
Main Methods:
- Exposure of Candida tropicalis to UV irradiation to induce mutations.
- Cultivation of mutant strains on glucose-containing solid medium to observe colony morphology.
- Microscopic examination to identify cellular characteristics (pseudohyphae, true hyphae).
- Pulsed-field gel electrophoresis (PFGE) to analyze karyotypes of parent and mutant strains.
Main Results:
- Four distinct morphological mutant types were identified: 'doughnut', 'frilly', 'echinoid', and 'walnut'.
- The 'doughnut' mutant exhibited a wrinkled colony with a hollow center, rich in pseudohyphal cells, and showed resemblance to the parent strain on oleic acid medium.
- 'Echinoid' mutants displayed echinulate colonies with aerial and true hyphae alongside pseudohyphae.
- Pulsed-field gel electrophoresis indicated karyotype differences in 'echinoid' and 'frilly' mutants compared to the parent strain.
Conclusions:
- UV irradiation is effective in generating diverse morphological mutants in Candida tropicalis.
- The identified mutants ('doughnut', 'frilly', 'echinoid', 'walnut') represent distinct phenotypic variations.
- Chromosomal rearrangements are suggested as a mechanism underlying the morphological changes observed in the 'echinoid' and 'frilly' mutants.