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