Comparative analysis of the intergenic spacer regions and population structure of the species complex of the pathogenic yeast Cryptococcus neoformans

Mara R. Diaz, Teun Boekhout, Traci Kiesling, Jack W. Fell

Research output: Contribution to journalArticlepeer-review

78 Scopus citations


Cryptococcus neoformans is an opportunistic basidiomycete responsible for the high incidence of cryptococcosis in patients with AIDS and in other immune-compromised individuals. This study, which focused on the molecular structure and genetic variability of the two varieties in the C. neoformans and Cryptococcus gattii species complex, employed sequence analysis of the intergenic spacer regions, IGSI and IGSII. The IGS region is the most rapidly evolving region of the rDNA families. The IGSI displayed the most genetic variability represented by nucleotide base substitutions and the presence of long insertions/deletions (indels). In contrast, the IGSII region exhibited less heterogeneity and the indels were not as extensive as those displayed in the IGSI region. Both intergenic spacers contained short, interspersed repeat motifs, which can be related to length polymorphisms observed between sequences. Phylogenetic analysis undertaken in the IGSI, IGSII and IGSI + 5S rRNA + IGSII regions revealed the presence of six major phylogenetic lineages, some of which segregated into subgroups. The major lineages are represented by genotypes 1 (C. neoformans var. grubii), genotype 2 (C. neoformans var. neoformans), and genotypes 3, 4, 5 and 6 represented by C. gattii. Genotype 6 is a newly described IGS genotypic group within the C. neoformans species complex. With the inclusion of IGS subgenotypic groups, our sequence analysis distinguished 12 different lineages. Sequencing of clones, which was performed to determine the presence of multiple alleles at the IGS locus in several hybrid strains, yielded a single IGS sequence type per isolate, thus suggesting that the selected group of cloned strains was mono-allelic at this locus. IGS sequence analyses proved to be a powerful technique for the delineation of the varieties of C. neoformans and C. gattii at genotypic and subgenotypic levels.

Original languageEnglish (US)
Pages (from-to)1129-1140
Number of pages12
JournalFEMS Yeast Research
Issue number12
StatePublished - Dec 2005
Externally publishedYes


  • Cryptococcus neoformans
  • Intergenic spacer (IGS)
  • Length polymorphism
  • Repeated motifs
  • Yeast

ASJC Scopus subject areas

  • Microbiology
  • Applied Microbiology and Biotechnology


Dive into the research topics of 'Comparative analysis of the intergenic spacer regions and population structure of the species complex of the pathogenic yeast Cryptococcus neoformans'. Together they form a unique fingerprint.

Cite this