Syncephalastrum racemosum

The genus Syncephalastrum is characterised by the formation of cylindrical merosporangia on a terminal swelling of the sporangiophore. Sporangiospores are arranged in a single row within the merosporangia. Syncephalastrum racemosum is the type species of the genus and a potential human pathogen; however, well-documented cases are lacking. It is found mainly from soil and dung in tropical and subtropical regions. It can also be a laboratory aerial contaminant. The sporangiophore and merosporangia of Syncephalastrum species may also be mistaken for an Aspergillus species, if the isolate is not examined carefully.

RG-2 organism

Syncephalastrum microscopy

Terminal vesicle, merosporangia and sporangiospores of Syncephalastrum racemosum.

Morphological description: 
Colonies are very fast growing, cottony to fluffy, white to light grey, becoming dark grey with the development of sporangia. Sporangiophores are erect, stolon-like, often producing adventitious rhizoids, and show sympodial branching (racemose branching) producing curved lateral branches. The main stalk and branches form terminal, globose to ovoid vesicles which bear finger-like merosporangia directly over their entire surface. At maturity, merosporangia are thin-walled, evanescent and contain five to ten (up to 18) globose to ovoid, smooth-walled sporangiospores (merospores). Maximum growth temperature 40C.

Key features: 
Mucorales, producing sympodially branching sporangiophores with terminal vesicles bearing merosporangia.

Domsch et al. (1980), McGinnis (1980), Onions et al. (1981), Rippon (1988), Samson et al. (1995), de Hoog et al. (2000, 2015), Ellis (2005b).

Antifungal susceptibility: Syncephalastrum racemosum very limited data (Espinel-Ingroff et al., 2015a and Australian national data); MIC µg/mL.
Antifungal No 0.016 0.03 0.06 0.125 0.25 0.5 1 2 4 8 16 ≥32
AMB 41   8 16 3 11 3            
ISAV 1             1          
VORI 6             1   4 1    
POSA 42   1 2 6 12 13 5 1 2      
ITRA 32   4 3 7 9 6   1     2