#BSCTalks: The role of hybridisation in the emergence of fungal pathogens
Channel: BSC CNS
Date: 2023-06-21

🗣By Valentina del Olmo, researcher from the Comparative Genomics group.

Hybridisation is a common event in yeasts often leading to genomic variability and adaptation. Candida orthopsilosis is a human-associated opportunistic pathogen belonging to the Candida parapsilosis species complex. Most C. orthopsilosis clinical isolates are hybrids resulting from at least four independent crosses between two parental lineages of which only one has been identified. The rare presence or total absence of parentals amongst clinical isolates is hypothesised to be a consequence of a reduced pathogenicity with respect to their hybrids.

We analysed the genomes of the first sequenced environmental C. orthopsilosis strains, which were isolated from warm marine ecosystems. We found that a majority of environmental isolates are hybrids, and that these are phylogenetically closely related to hybrid clinical isolates. Furthermore, we identified the long-sought missing parental lineage, thus providing a complete overview of the genomic evolution of this species. Additionally, we discovered phenotypic differences between the two parental lineages, as well as between parents and hybrids, under conditions relevant for pathogenesis. 

Our results suggest a marine origin of C. orthopsilosis hybrids, with intrinsic pathogenic potential, and pave the way to identify the pre-existing environmental adaptations that rendered hybrids more prone than parental lineages to colonise and infect the mammalian host.