Affiliation:
1. Departments of Molecular Genetics and Microbiology
2. Medicine
3. Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710
Abstract
ABSTRACT
The ecological niche that 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 that an organism can occupy represents the fundamental niche. The growth and development of
Cryptococcus neoformans
and
Cryptococcus gattii
on pigeon guano were examined to determine whether these two species occupy the same or different ecological niches.
C. neoformans
is a cosmopolitan pathogenic yeast that infects predominantly 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 immunocompetent individuals and is associated with geographically restricted environments, most notably, eucalyptus trees. Pigeon guano supported the 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 observations that
C. neoformans
completes the life cycle on pigeon guano but that
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.
Publisher
American Society for Microbiology
Subject
Molecular Biology,General Medicine,Microbiology
Cited by
150 articles.
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