Mycocladus corymbifera

Synonym: Absidia corymbifera

Reference: Hoffman et al. 2007.  Revision of the genus Absidia (Mucorales, Zygomycetes) based on physiological, phylogenetic, and morphological characters, thermotolerant Absidia spp. form a coherent group, Mycocladiaceae fam. nov.  Mycological Research 111:1169-1183.

The genus Absidia is characterized by a differentiation of the hyphae into arched stolons bearing more or less verticillate sporangiophores at the internode, and rhizoids formed at the point of contact with the substrate (at the node).  This feature separates species of Absidia from the genus Rhizopus, where the sporangia arise from the nodes and are therefore found opposite the rhizoids. The sporangia are relatively small, globose, pyriform- or pear-shaped and are supported by a characteristic funnel-shaped apophysis. This distinguishes Absidia from the genera Mucor and Rhizomucor, which have large, globose sporangia without an apophysis. Absidia currently contains 21 mostly soil-borne species. A. corymbifera is the only species of Absidia known to cause disease in man and animals.

Mycocladus (Absidia) corymbifera showing a typical pyriform-shaped sporangium with a conical-shaped columella and pronounced apophysis.

Colonies are fast growing, floccose, white at first becoming pale grey with age, and up to 1.5 cm high. Sporangiophores are hyaline to faintly pigmented, simple or sometimes branched arising solitary from the stolons, in groups of three, or in whorls of up to seven. Rhizoids are very sparingly produced and may be difficult to find without the aid of a dissecting microscope to examine the colony on the agar surface. Sporangia are small (10-40 um in diameter) and are typically pyriform in shape with a characteristic conical-shaped columella and pronounced apophysis, often with a short projection at the top.  Sporangiospores vary from subglobose to oblong-ellipsoidal (3.0-7.0 x 2.5-4.5 um), are hyaline to light grey and are smooth-walled.  Temperature: optimum 35-37C; maximum 45C. RG-2 organism.

MIC data is limited.  Antifungal susceptibility testing of individual strains is recommended.

Clinical significance:

Absidia corymbifera is a common human pathogen, causing pulmonary, rhinocerebral, disseminated, CNS or cutaneous types of infection. It is also often associated with animal disease, especially mycotic abortion. A. corymbifera has a world-wide distribution mostly in association with soil and decaying plant debris.

Mycosis: Zygomycosis

Further reading:

Domsch, K.H., W. Gams, and T.H. Anderson. 1980. Compendium of soil fungi. Volume 1. Academic Press, London, UK.

Kwon-Chung, K.J. and J.E. Bennett. 1992. Medical Mycology. Lea & Febiger, Philadelphia and London.