DESCRIPTIONS OF MEDICAL FUNGI

Descriptions of Medical Fungi 167
RG-2 organism.
Rhizomucor pusillus (Lindt) Schipper
Morphological Description: Cultures are characterised by compact, low growing
(2-3 mm high), grey to greyish brown-coloured mycelium and by the development of
typical sympodially branched, hyaline to yellow-brown sporangiophores (8-15 μm in
diameter), always with a septum below the sporangium. Sporangia are globose (40-60
µm in diameter), each possessing an oval or pear-shaped columella (20-30 µm), often
with a collarette. Sporangiospores are hyaline, smooth-walled, globose to subglobose,
occasionally oval (3-5 µm), and are often mixed with crystalline remnants of the
sporangial wall. Chlamydospores are absent. Zygospores are rough-walled, reddish
brown to black, 45-65 µm in diameter and may be produced throughout the aerial
hyphae in matings between compatible isolates. Temperature growth range: minimum
20-27 O C; optimum 35-55 O C; maximum 55 O C. There is positive assimilation of sucrose
and no thiamine dependence.
Key Features: Mucorales, growth at 45 O C (thermophilic), poorly developed stolons
and rhizoids, branching sporangiophores with a septum below the sporangium, darkcoloured
sporangia without apophyses and smooth-walled globose to subglobose
sporangiospores.
20 µm
b
a
15 µm
Rhizomucor pusillus (a) sporangiophores, collumellae and (b) primitive rhizoids.
Antifungal Susceptibility: R. pusillus (Espinel-Ingroff et al. 2015a, Australian
National data); MIC µg/mL.
No. 32
AmB 36 3 8 9 12 1 2 1
POSA 36 1 5 11 11 7 1
ITRA 18 3 6 4 3 1 1