Basidiobolus microsporus (R.K. Benjamin 1962) is a
gastrointestinal gut fungus of reptiles and amphibians. The
type culture was isolated from lizard dung, but the species is also
known from the dung of other reptiles and amphibians and from
soil. B. microsporus grows easily on synthetic media
(e.g., corn meal agar), producing hyaline vegetative hyphae that
become segmented by the development of cross walls resulting in
uninucleate hyphal segments. Intercalary hyphal segments
frequently become emptied of cytoplasm due to spore production or
concentrated in terminal hyphal segments.
Like other species of Basidiobolus, B.
microsporus produces multiple spore types including
smooth-walled zygospores (meiospores) typically formed through the
conjugation of adjacent hyphae, and multiple types of asexual
spores including: chlamydospore-like hyphal bodies, and forcibly
ejected, globos primary spores, which may develop into sporangia
that give rise to endogenous sporangiospores, or germinate a
sporophore that produces adhesive spores for dispersal by
insects. Unique to B. microsporous, and the basis of
its name, are apically elongated microspores that develop
exogenously from sporangiospores. As such, Basidiobolus
has evolved numerous spore types that function in dispersal by
insects, forcible dispersal through air, and resting spores for
long-term survival in the host gut and in the environment.
Basidiobolus has several unique genetic and genomic
features, which distinguish it from the rest of fungal world. It
has possibly the largest nuclei among all known fungi. Its genome
has been reported to contain a significant HGT signal from
co-occurring gut bacteria. Furthermore, the structure of its
mitosis-associated organelle is similar to the centrioles of all
flagellated eukaryotes, and its genome is comprised of a large
number of small chromosomes. As such, Basidiobolus
represents a system of gut fungi that exhibits noncanonical traits
in fungal evolution.
