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Eukaryotic Cell doi:10.1128/EC.00097-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Cryptococcus neoformans mates on pigeon guano: implications for the realized ecological niche and globalization

Departments of Molecular Genetics and Microbiology, Medicine, Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710 USA

^* To whom correspondence should be addressed. Email: heitm001{at}duke.edu.

	Abstract

The ecological niche a species can occupy is determined by its resource requirements and the physical conditions necessary for survival. The niche to which an organism is most highly adapted is the realized niche, whereas the complete range of habitats an organism can occupy represents the fundamental niche. Growth and development of Cryptococcus neoformans and Cryptococcus gattii on pigeon guano was examined to determine whether these two species occupy the same or different ecological niches. C. neoformans is a cosmopolitan pathogenic yeast that predominantly infects immunocompromised individuals, exists in two varieties - grubii (serotype A) and neoformans (serotype D), and is commonly isolated from pigeon guano worldwide. By contrast, C. gattii often infects immuncompetent individuals, and is associated with geographically restricted environments, most notably eucalyptus trees. Pigeon guano supported growth of both species and a brown pigment related to melanin, a key virulence factor, was produced. C. neoformans exhibited prolific mating on pigeon guano, whereas C. gattii did not. The observation that C. neoformans completes the life cycle on pigeon guano but C. gattii does not indicates that pigeon guano could represent the realized ecological niche for C. neoformans. Because C. gattii grows on pigeon guano but cannot sexually reproduce, pigeon guano represents a fundamental but not a realized niche for C. gattii. Based on these studies, we hypothesize that an ancestral Cryptococcus strain gained the ability to sexually reproduce in pigeon guano and then swept the globe.

This article has been cited by other articles:

• Sun, S., Xu, J. (2007). Genetic Analyses of a Hybrid Cross Between Serotypes A and D Strains of the Human Pathogenic Fungus Cryptococcus neoformans. Genetics 177: 1475-1486 [Abstract] [Full Text]