Cryptococcus neoformans Recovered 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 seven 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). 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 five 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.

Environmental Status of Cryptococcus neoformans and Cryptococcus gattii in Colombia

“…Regarding genotypes, C. gattii VGII is the most common in clinical isolates, while the VGIII genotype is less frequent [ 102 ]. However, in the study by Escandon et al, the most common phenotype determined in environmental isolates was VGIII, in agreement with the results reported by Firacative et al in 2011, although to a lesser extent [ 26 , 57 ]. Additionally, the predominant genotype for clinical isolates of C. neoformans is VNI [ 102 , 103 ], which coincides with the genotype determined in environmental samples [ 18 , 26 , 27 ].…”

“…Additionally, the C. neoformans complex has been reported in tree species, with higher prevalence compared to the C. gattii complex, for example in Eucalyptus spp. [ 55 , 56 ], Terminalia catappa [ 22 ], Olea europea [ 57 ], and Ceratonia (carob tree) [ 55 ].…”

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 ).…”

Combining natural language processing and metabarcoding to reveal pathogen-environment associations

“…However, the closely related species Cryptococcus gattii [11], responsible for the Vancouver Island (BC, Canada) outbreak of cryptococcosis in 1999, is documented to be associated with the bark of a variety of tree species (potentially over 50) [12]. Several recent studies have also found C. neoformans isolates in association with trees, such as eucalyptus in Egypt [13], and olive in Turkey [14]. (note: at least a dozen such papers) Furthermore, recent work has shown that C. neoformans is able to grow both on live plant material, such as Arabidopsis seedlings and Douglas fir trees, as well as in saprobic association with dead plant materials [15].…”