Isolation of a Cryptococcus neoformans serotype A MATa strain from the Italian environment

Cryptococcus neoformans is a heterothallic basidiomycete which possesses a bipolar mating system based on two mating type alleles, MAT alpha and MAT a lpha In the type variety, C. neoformans var. neoformans, both mating types have been found among strains of one serotype, serotype D, whereas only MAT alpha was identified after extensive survey of serotype A strains. Serotyp e A MAT alpha appeared to be extinct or to exist only in a vestigial, non-f unctional form. We report the isolation of a C. n. var. neoformans serotype A MAT alpha strain from the Italian environment. The strain was serotyped by slide agglutination test, genotyped by polymerase chain reaction (PCR) f ingerprinting using the (GACA)(4) primer, and its haploid state was determi ned by flow cytometry. The mating type was identified by PCR amplification of the pheromone a gene. In addition, the amplification of the four STE20 a lleles, specific for the mating type of serotypes A and D, showed that the strain contains only the MAT alpha locus. By crossing experiments the strai n was found to be fertile. The interest in the finding of this fertile isol ate is related to the possibility to construct a congenic pair of serotype. A MAT alpha /MAT alpha strains to be used in genetic and pathogenesis stud ies.