RT Journal Article SR Electronic(1) A1 Keller, S. M. A1 Viviani, M. A. A1 Esposto, M. C. A1 Cogliati, M. A1 Wickes, B. L.YR 2003 T1 Molecular and genetic characterization of a serotype A MATaCryptococcus neoformans isolate JF Microbiology, VO 149 IS 1 SP 131 OP 142 DO https://doi.org/10.1099/mic.0.25921-0 PB Microbiology Society, SN 1465-2080, AB Cryptococcus neoformans comprises two varieties (neoformans and gattii) and four serotypes (A, B, C and D). Fertile isolates of both mating types have been identified in serotypes B, C and D; however, a fertile serotype A MAT a strain has not been confirmed, although serotype A MATα strains will mate with serotype D MAT a strains. Preliminary analysis of a recent Italian environmental isolate (IUM 96-2828) suggested that this strain was haploid, serotype A and MAT a. In this study, IUM 96-2828 has been characterized in detail. A mating reaction between IUM 96-2828 and H99 (serotype A MATα) produced abundant spores with an equal distribution of MAT a and MATα progeny, all of which were serotype A. Karyotypic analysis of F1 spores revealed evidence of recombination, confirming that IUM 96-2828 was fertile. The MAT a pheromone gene from IUM 96-2828 was sequenced and found to be most closely related to the serotype D MAT a pheromone gene. Phylogenetic comparisons of other genes not linked to mating type also suggested IUM 96-2828 was most closely related to serotype A strains. Biochemical analysis showed that the carbon assimilation profiles of H99 and IUM 96-2828 were identical for 97 % (30/31) of the substrates while isozyme analysis showed 89 % (17/19) identity. Assays of major virulence factors found no difference between H99 and IUM 96-2828. Virulence studies using the mouse model demonstrated that IUM 96-2828 was virulent for mice, although it was less virulent than H99. These data strongly suggest that IUM 96-2828 is a true haploid serotype A MAT a isolate that is fertile., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.25921-0