DESCRIPTIONS OF MEDICAL FUNGI

Descriptions of Medical Fungi 111
Synonymy: Mycocladus corymbifera (Cohn) J.H. Mirza.
Absidia corymbifera (Cohn) Saccardo & Trotter.
Mucor corymbifera Cohn.
Recent taxonomic revisions of the genus Absidia have placed the thermotolerant
species into the genus Lichtheimia (Hoffmann et al. 2007, 2009). The genus Lichtheimia
currently contains five mostly saprophytic plant decaying and soil-borne species.
Lichtheimia corymbifera is the principle pathogen causing human and animal infections,
however L. ramosa and L. ornata have also been reported as human pathogens (often
misidentified morphologically as L. corymbifera) (Alastruey-Izquierdo et al. 2010).
RG-2 organism.
Lichtheimia corymbifera (Cohn) Vuill.
Morphological Description: 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 solitarily or in groups. Subsporangial
septa are absent or rare. 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 µm 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 oblongellipsoidal
(3-7 x 2.5-4.5 µm), hyaline to light grey and smooth-walled. Intercalary giant
cells may also be present. Temperature: optimum 35-37 O C; maximum 46 O C.
Key Features: Mucorales, small pyriform-shaped sporangia with a characteristic
conical-shaped columellae and pronounced apophyses, rapid growth at 40 O C.
Comment: Morphological characteristics alone are not sufficient to reliably differentiate
between L. corymbifera, L. ramosa and L. ornata. While L. ornata develops large, densely
branched giant cells and L. ramosa has more ellipsoidal to cylindrical sporangiospores
and a faster growth rate, these characters are often difficult to interpret. Molecular
methods are needed to accurately separate these species.
Molecular Identification: Species recognition in Lichtheimia is based on ITS and/or
D1/D2 sequencing (Garcia-Hermoso et al. 2009, Alastruey-Izquierdo et al. 2010).
MALDI-TOF MS: Direct identification of Lichtheimia species was described by Schrödl
et al. (2012).
References: Ellis and Hesseltine (1965, 1966), Hesseltine and Ellis (1964a, 1966),
Nottebrock et al. (1974), O’Donnell (1979), Samson et al. (1995), Domsch et al. (1980),
McGinnis (1980), Ellis (2005b), de Hoog et al. (2000, 2015).