Evidence of Sexual Recombination amongCryptococcus neoformansSerotype A Isolates in Sub-Saharan Africa

The most common cause of fungal meningitis in humans,Cryptococcus neoformansserotype A, is a basidiomycetous yeast with a bipolar mating system. However, the vast majority (>99.9%) ofC. neoformansserotype A isolates possess only one of the two mating type alleles (MATα). Isolates with the other allele (MATa) were recently discovered and proven to mate in the laboratory. It has been a mystery whether and whereC. neoformansstrains undergo sexual reproduction. Here, we applied population genetic approaches to demonstrate that a population ofC. neoformansserotype A clinical isolates from Botswana contains an unprecedented proportion of fertileMATa isolates and exhibits evidence of both clonal expansion and recombination within two partially genetically isolated subgroups. Our findings provide evidence for sexual recombination among some populations ofC. neoformansserotype A from sub-Saharan Africa, which may have a direct impact on their evolution.

A new species of Hypholoma (Agaricales) from Western Australia

Hypholoma australe sp. nov., a primary wood decomposer, is described and illustrated from Western Australia. It appears to be closely related to Hypholoma sublateritium (Fr.) Quél, which is widespread in the Northern Hemisphere. Self crosses of both species reveal a bipolar mating system. Mating tests carried out between single-spore isolates from populations from Western Australia and North America were completely intersterile.

Conjugation and chlamydospores in Sporobolomyces odorus

Conjugation was observed in mix-mated pairs of 16 Sporobolomyces odorus isolates. The mating tests suggest a simple bipolar mating system. Conjugation resulted in the development of dikaryotic hyphae with clamp connections, and in chlamydospore formation. This dikaryotic phase closely resembled that of Sporidiobolus johnsonii. The chlamydospores germinated by the production of promycelium-like structures or of dikaryotic hyphae.