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Analysis of ploidy and sexual characteristics of natural isolates of Cryptococcus neoformans
Abstract:
We report here an extensive examination of the ploidy of a basidiomycetous yeast. The ploidy of 34 strains of Cryptococcus neoformans var. neoformans, isolated mostly from Japanese patients, was determined by means of quantitative fluorescence microscopy after DNA staining with propidium iodide. The sexual characteristics of the strains including the two tester strains were as follows. Twenty-four strains were of the heterothallic alpha type, 1 was of the heterothallic a type, and 2 were self fertile; the remaining 7 showed no sexual response. The following strains were found to be haploid: the heterothallic a strain, 20 of the 24 heterothallic alpha strains, and 3 of the 7 asexual strains. Thus, the C. neoformans strains were mostly haploid, as the sexual response of this organism suggests. Both of the self-fertile strains and four of the seven asexual strains were diploid. Unexpectedly, 4 of the 24 heterothallic alpha strains were diploid.
Insights
This study examined the ploidy of Cryptococcus neoformans yeast strains from Japanese patients. Most strains were haploid, aligning with the organism
Area of Science:
- Mycology
- Genetics
- Microbiology
Background:
- Cryptococcus neoformans var. neoformans is an important basidiomycetous yeast.
- Understanding its ploidy is crucial for studying its genetics and pathogenicity.
Purpose of the Study:
- To determine the ploidy of 34 Cryptococcus neoformans var. neoformans strains.
- To correlate ploidy with the sexual characteristics of these yeast strains.
Main Methods:
- Quantitative fluorescence microscopy was employed.
- DNA staining with propidium iodide was used for ploidy determination.
- Sexual characteristics of 34 strains were assessed.
Main Results:
- The majority of Cryptococcus neoformans var. neoformans strains examined were haploid.
- Haploid strains included the heterothallic 'a' type, most heterothallic 'alpha' types, and some asexual strains.
- Diploid strains were identified among self-fertile and asexual strains, with an unexpected finding of diploid heterothallic 'alpha' strains.
Conclusions:
- Cryptococcus neoformans var. neoformans strains are predominantly haploid, consistent with expectations based on sexual behavior.
- The presence of diploid strains, particularly among heterothallic 'alpha' types, warrants further investigation into their genetic and clinical significance.