Comparison of the electrophoretic karyotypes and chromosomal location of ten genes in the two varieties of Cryptococcus neoformans

We compared multiple isolates of the two varieties of Cryptococcus neoformans, as well as previously characterized representative isolates, for their electrophoretic karyotypes using pulsed-field electrophoresis. The two varieties could be clearly distinguished based upon the size of the smallest chromosome. The smallest chromosome for isolates of the gattii variety (serotypes B and C) was found to be 400-700 kb in size. The smallest chromosome for isolates of the neoformans variety was consistently found to be larger, approximately 770 kb in size. Isolates of the gattii variety averaged 13 chromosomes while the neoformans variety averaged 12. The size of the Cryptococcus genome was found to be approximately 23 megabases. Isolates of C. neoformans var. neoformans tended to be more conserved than those of var. gattii with regard to gene position.