Basidiobolales
Overview
The order contains one family, Basidiobolaceae, one genus, Basidiobolus, and five species. These fungi are defined by the presence of a subsporangial vesicle which ruptures during sporangial dehiscence, the sporangia and some cells may appear multispored because of the production of internal protoplasts, accessory cells are formed on the gametangia, and all cells are uninucleate with the nuclei being relatively large and having a conspicuous, central nucleous but no heterochromatin.
Basidiobolales was proposed because of the placement of Basidiobolus with the Chytridiomycota in several phylogenetic studies using nuclear SSU rDNA sequences (Nagahama et al., 1995; Jensen et al., 1998 James et al., 2000; Tanabe et al., 2000; Tehler et al., 2003). Ultrastructural examination using TEM has shown that Basidiobolus also produces a nucleus-associated organelle that resembles a centriole with microtubules; a flagellum is not produced (McKerracher and Heath 1985).
Lutzoni et al. (2004), however, found that a Bayesian analysis of nuclear LSU and SSU rDNA sequences placed Basidiobolus in the Zygomycota but it was not close to the remaining Entomophthorales. Keeling (2003) using α-tubulin and β-tubulin sequences and Tanabe et al. (2003) using EF-1α and RPB1 sequences also revealed that Basidiobolus was included in the Zygomycota but again it was not close to the Entomopthorales.
Molecular phylogenetic studies thus far have shown that Basidiobolus may not be closely related to the core Entomophthorales. It is unclear what the true affinities of the Basidiobolales are at this time. The final disposition of Basidiobolus may have to await phylogenetic analysis using sequences from additional genes.
Species of Basidiobolus can be isolated from dung and humus. Some species of Basidiobolus produce zygomycosis in humans (Gugnani, 1999).
Basidiobolales T. Cavalier-Smith, 1998 (Biol. Rev. 73:246).
Saprobes, occurring in soil or in the dung of amphibians or reptiles; may be weakly pathogenic in vertebrates. Mycelium more or less extensive, composed of uninucleate cells; often forming uninucleate hyphal bodies; uninucleate yeast cells sometimes produced; some cells may appear multispored following internal proliferation of the protoplast. Sporophores usually unbranched, developing a terminal, subsporal vesicle. Primary spores forcibly discharged by rupture of the subsporal vesicle. Spores unitunicate, uninucleate, spheroidal, often appearing multispored following internal proliferation of protoplasts. Secondary spores like the primary but smaller, or capillispores or microspores. Chlamydospores often produced. Zygospores smooth or undulate, formed in one of a pair of gametangia arising from adjacent hyphal segments; each mature gametangium bearing a uninucleate, beaklike accessory cell. Nuclei large (over 10 μm in length), with a conspicuous central nucleolus, no heterochromatin.
Type family: Basidiobolaceae.
Updated Feb 09, 2005