DESCRIPTIONS OF MEDICAL FUNGI

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Descriptions of Medical Fungi
The genus Rhizomucor is distinguished from Mucor by the presence of stolons and
poorly developed rhizoids at the base of the sporangiophores and by the thermophilic
nature of its two species: R. miehei and R. pusillus. Both of these species are potential
human and animal pathogens and were originally classified in the genus Mucor.
Rhizomucor pusillus is cosmopolitan and both R. miehei and R. pusillus have been
reported as pathogens to humans and animals, the latter to a greater extent.
References: Cooney and Emerson (1964), Schipper (1978), Domsch et al. (1980),
McGinnis (1980), Ellis and Keane (1981), Scholer et al. (1983), de Hoog et al. (2000,
2015), Schipper and Stalpers (2003) and Ellis (2005b).
Identification of most Mucorales is based primarily on the morphology of the sporangia;
i.e. arrangement and number of sporangiospores, shape, colour, presence or absence
of columellae and apophyses, as well as the arrangement of the sporangiophores and
the presence or absence of rhizoids. Growth temperature tests can also be especially
helpful in identifying and differentiating members of the genera Rhizomucor, Rhizopus
and Lichtheimia.
Rhizomucor miehei (Cooney and Emerson) Schipper
Synonymy: Mucor miehei Lindt.
This species has been reported as a rare cause of bovine mastitis (Scholer et al. 1983)
and is similar in many respects to R. pusillus.
RG-1 organism.
Rhizomucor Lucet & Costantin
Morphological Description: All strains are homothallic forming numerous zygospores,
which are reddish-brown to blackish-brown, globose to slightly compressed, up to 50
µm in diameter, with stellate warts and equal suspensor cells. Colony colour is a dirty
grey rather than brown, and sporangia have spiny walls, are up to 50-60 µm in diameter,
with columellae rarely larger than 30 µm in diameter. Growth is stimulated by thiamine,
with no assimilation of sucrose and maximum growth temperature is 54-58 O C.
Key Features: Growth at 45 O C, the formation of numerous zygospores, a dirty grey
culture colour and a partial growth requirement for thiamine.
Synonymy: Mucor pusillus Lindt.
Rhizomucor pusillus (Lindt) Schipper
This species is a rare human pathogen. It has been reported from cases of pulmonary,
disseminated and cutaneous types of infection. It is more often associated with animal
disease, especially bovine abortion. Rhizomucor pusillus has a worldwide distribution
and is commonly associated with compost heaps.