Ecology and Environmental Niche
C. neoformans was first cultivated by Sanfelice from fermenting peach juice in 1894, and it was initially named Saccharomyces neoformans. In 1901, Jean-Paul Vuillemin renamed the organism C.
neoformans because it did not produce ascospores, a defining characteristic of the Saccharomyces (Barnett 2010). Emmons later (Emmons 1951, 1955) isolated the fungus from soil and pigeon excreta. The species C. neoformans has also been recovered from the guano of other avian species, including chickens, parrots, sparrows, skylarks, starlings, canaries, and turtledoves (Muchmore et al. 1963; Littman and Walter 1968; Bauwens et al. 1986, DeVroey and Swinne 1986, Hedayati et al. 2011), as well as from the nares and upper respiratory tract of cats, dogs, koalas, and ferrets with or without cryptococcosis (Malik et al. 1995, 1997, 2002; Sorrell et al. 1996; Lester et al. 2004; Morera et al. 2014; Danesi et al. 2014b). Soil has been suggested to represent a more inhospitable environment for C. neoformans than avian excrement (Ruiz et al. 1981). Moreover, C. neoformans is occasionally isolated from various nonavian sources (Pal and Baxter 1985; Swinne et al. 1986) and decaying wood debris within living tree hollows; its association with tree hollows is, however, weaker than that of C. gattii (Klein 1901; Nawange et al. 2006; Grover et al. 2007).The first isolation of C. gattii (VGI) from the environment was reported from the wood, bark, leaves, and plant debris of Eucalyptus Camaldulensis trees in Australia (Ellis and Pfeiffer 1990). Thereafter, C. gattii has been isolated from Eucalyptus trees in tropical and subtropical regions of Brazil (Montenegro and Paula 2000), other countries in South America (Ellis and Pfeiffer 1990; Bava and Negroni 1992; Castanon-Olivares et al. 2000), Mexico (Castanon-Olivares Castanon-Olivares et al. 2000), North America (Kwon-Chung and Bennett 1984; Clancy et al.
1990; Levitz1991), the region around the Mediterranean Basin (Mseddi et al. 2011; Elhariri et al. 2016; Cogliati et al. 2016), Malaysia (Keah et al. 1994), Australia (Pfeiffer and Ellis
1992), India (Padhye et al. 1993; Chakrabarti et al. 1997), and China (Li et al. 1993). Of note, the two known host trees of C. gattii, E. camaldulensis and Eucalyptus tereticornis, do not occur naturally in the “Top End” of the Northern Territory of Australia. Therefore, the isolation of a separate molecular type of C. gattii as “VGII” from different trees in this region strongly suggested the existence of an alternative environmental niche for C. gattii (Chen et al. 1997a). C. gattii has been isolated from more than 50 tree species, mostly angiosperms (such as Ceratonia, Eucalyptus spp., Ficus spp., Mangifera indica, Olea spp., Pithecellobium dulce, Quercus garryana, Syzygium cumini, Tamarindus indica, and Terminalia spp.), and less frequently from the gymnosperms (such as Abies spp., Arbutus menziesii var. menziesii, Cedrus spp., Cupressus lusitanica, Cupressus sempervirens, Picea spp., Pinus spp., Pseudotsuga menziesii var. menziesii, and Thuja plicata) in North America, South America, Africa, India, and the Mediterranean Basin (Randhawa et al. 2003; Kidd et al. 2004; Grover et al. 2007; Springer and Chaturvedi 2010; Cogliati 2013, 2016). Gymnosperms and angiosperms have in common the ability to develop decayed hollows but differ in biochemical composition, available nutrients, water content, microbial communities, and fungal associations (Lazera et al. 1998; Springer and Chaturvedi 2010).
C. gattii has also been recovered from several wild animals, including African grey parrots (Sorrell et al. 1996) and koalas (Ellis and Pfeiffer 1990; Krockenberger et al. 2003), as well as from bat guano (Lazera et al. 1993), ostrich feathers, and camel hair (Montagna et al. 1996). In Australia, the persistence and amplification of C. gattii in the environment have been attributed to koalas feeding on Eucalyptus trees (Ellis and Pfeiffer 1990; Krockenberger et al. 2003), in concert with the effects of their abrading wooden surfaces and providing nutrients to fungi from their urine and/or feces.
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