DESCRIPTIONS OF MEDICAL FUNGI

Descriptions of Medical Fungi 135
Synonymy: Rhizomucor variabilis Zheng & Chen.
RG-2 organism.
Morphological Description: Colonies are whitish to ochraceous, with buff-ochre
reverse. Sporangiophores arising from hyphae or from stolons; rhizoids abundant.
Sporangiophores are hyaline, up to 2 mm long, 9-23 μm wide, simple or once branched,
with branches terminating at a higher level than the main stems; branches all ending in
a sporangium. Sporangia subspherical to spherical, up to 100 μm diameter. Columella
spherical, ellipsoidal to cylindrical, about 40 μm wide, sometimes lobed, with or without
an apophysis. Sporangiospores are hyaline, smooth-walled, very variable, mostly
subspherical to ellipsoidal, 3-11 × 2-7 μm. Chlamydospores are abundant. Maximum
growth temperature 38 O C.
Comment: Mucor irregularis differs from other species of Mucor by having abundant
rhizoids of different sizes and sporangiospores of highly variable shape, mostly
subspherical to ellipsoidal (Lu et al. 2009, 2013). This species is closely related to
Mucor hiemalis (Voigt et al. 1999).
RG-1 organism.
Mucor irregularis Stchigel et al.
Mucor ramosissimus Samutsevich
Morphological Description: Colonial growth is restricted, greyish and does not
grow at 37 O C (maximum temperature for growth is 36 O C). Sporangiophores are
hyaline, slightly roughened, tapering towards the apex and are erect with repeated
sympodial branching. Sporangia are grey to black, globose or somewhat flattened,
up to 80 µm in diameter and have very persistent sporangial walls. Columellae are
applanate (flattened), up to 40-50 µm in size and are often absent in smaller sporangia.
Sporangiospores are faintly brown, smooth-walled, subglobose to broadly ellipsoidal,
5-8 x 4.5-6 µm in size. Oidia may be present in the substrate hyphae, chlamydospores
and zygospores are absent. Assimilation of ethanol is negative and that of nitrate is
positive.
Comment: Mucor ramosissimus differs from other species of Mucor by its low, restricted
growth on any medium, extremely persistent sporangial walls, columellae that are
applanate or absent in smaller sporangia (often resembling Mortierella species), short
sporangiophores that repeatedly branch sympodially as many as 12 times, and the
occurrence of racket-shaped enlargements in the sporangiophores (Hesseltine and
Ellis 1964b, Schipper 1976, Scholer et al. 1983, de Hoog et al. 2000, Schipper and
Stalpers 2003).
Antifungal Susceptibility: M. ramosissimus (Espinel-Ingroff et al. 2015a, Australian
National data); MIC µg/mL.
No. 16
AmB 19 2 4 3 6 1 1
POSA 13 4 4 2 2 1