Cryptococcus neoformansrecovered from olive trees (Olea europaea) in Turkey reveal allopatry with African and South American lineages

Abstract

Cryptococcus species are life-threatening human fungal pathogens that cause cryptococcal meningoencephalitis in both immunocompromised and healthy hosts. The natural environmental niches of Cryptococcus include pigeon (Columba livia) guano, soil, and a variety of tree species such as Eucalyptus camaldulensis, Ceratonia siliqua, Platanus orientalis, and Pinus spp. Genetic and genomic studies of extensive sample collections have provided insights into the population distribution and composition of different Cryptococcus species in geographic regions around the world. However, few such studies examined Cryptococcus in Turkey. We sampled 388 Olea europaea (olive) and 132 E. camaldulensis trees from 7 locations in coastal and inland areas of the Aegean region of Anatolian Turkey in September 2016 to investigate the distribution and genetic diversity present in the natural Cryptococcus population. We isolated 84 Cryptococcus neoformans strains (83 MATα and 1 MATa) and 3 Cryptococcus deneoformans strains (all MATα) from 87 (22.4% of surveyed) O. europaea trees; a total of 32 C. neoformans strains were isolated from 32 (24.2%) of the E. camaldulensis trees, all of which were MATα. A statistically significant difference was observed in the frequency of C. neoformans isolation between coastal and inland areas (P < 0.05). Thus, O. europaea trees could represent a novel niche for C. neoformans. Interestingly,the MATa C. neoformans isolate was fertile in laboratory crosses with VNI and VNB MATα tester strains and produced robust hyphae, basidia, and basidiospores, thus suggesting potential sexual reproduction in the natural population. Sequencing analyses of the URA5 gene identified at least 5 different genotypes among the isolates. Population genetics and genomic analyses revealed that most of the isolates in Turkey belong to the VNBII lineage of C. neoformans, which is predominantly found in southern Africa; these isolates are part of a distinct minor clade within VNBII that includes several isolates from Zambia and Brazil. Our study provides insights into the geographic distribution of different C. neoformans lineages in the Mediterranean region and highlights the need for wider geographic sampling to gain a better understanding of the natural habitats, migration, epidemiology, and evolution of this important human fungal pathogen.

POPULATION GENOMIC ANALYSIS OF CRYPTOCOCCUS BRAZILIAN ISOLATES REVEALS AN AFRICAN TYPE SUBCLADE DISTRIBUTION

“…More recently, the improvement of sequencing technologies and bioinformatics tools allowed analysis of whole genome sequences, revealing new details in the structure and global geographical distribution of the Cryptococcus populations together with the identification of additional clades and subclades (Farrer et al 2019). Most of these studies focused on C. neoformans, with >1000 C. neoformans genome sequences analyzed in four studies (Desjardins et al 2017;Rhodes et al 2017b;Vanhove et al 2017;Ashton et al 2019;Ergin et al 2019). Through these efforts, the VNB clade has been separated into the VNBI and VNBII subclades, which have different resistance to oxidative stress and a different ability to produce melanin (Desjardins et al 2017;Vanhove et al 2017).…”