The genus Madurella was originally based on tissue morphology (mycetoma with black grains) and the formation of sterile cultures on mycological media.
Initially two species were described, M. mycetomatis and M. grisea. However recent molecular studies have recognised five species: Madurella mycetomatis, Trematosphaeria grisea (formerly M. grisea), M. fahalii, M. pseudomycetomatis and M. tropicana (Desnos-Ollivier et al. 2006, de Hoog et al. 2004a, 2012). All species have been isolated from soil and are major causative agents of mycetoma.
Colonies are slow growing, flat and leathery at first, white to yellow to yellowish-brown, becoming brownish, folded and heaped with age, and with the formation of aerial mycelia. A brown diffusible pigment is characteristically produced in primary cultures. Although most cultures are sterile, two types of conidiation have been observed, the first being flask-shaped phialides that bear rounded conidia, the second being simple or branched conidiophores bearing pyriform conidia (3-5 µm) with truncated bases. The optimum temperature for growth of this mould is 37C.
Grains of Madurella mycetomatis (tissue microcolonies) are brown or black, 0.5-1.0 mm in size, round or lobed, hard and brittle, composed of hyphae which are 2-5 µm in diameter, with terminal cells expanded to 12-15 (30) µm in diameter.
M. mycetomatis can be distinguished from Trematosphaeria grisea by growth at 37C and its inability to assimilate sucrose.
Black grain mycetoma, growth at 37C, diffusible brown pigment produced on culture and the occasional presence of phialides.
ITS sequencing is recommended for species separation (Ahmed et al. 2014b, Desnos-Olliver et al. 2006, Irinyi et al. 2015). A five locus phylogenetic analysis was performed by Ahmed et al. (2014a) using the ITS, D1/D2, RPB2 and EF-1α genes.
McGinnis (1980), Chandler et al. (1980), Rippon (1988), de Hoog et al. (2000, 2004a, 2012, 2015), Desnos-Ollivier et al. (2006).
Colonies are slow growing, dark, leathery, folded with radial grooves and with a light brown to greyish surface mycelium. With age, colonies become dark brown to reddish-brown and have a brownish-black reverse. Microscopically, cultures are sterile, although hyphae of two widths have been described, thin at 1-3 µm in width or broad at 3-5 µm in width. The optimum temperature for growth of T. grisea is 30C; this fungus does not grow at 37C.
Trematosphaeria grisea can be distinguished from Madurella mycetomatis by the inability to grow at 37C and to assimilate lactose.
Black grain mycetoma, no growth at 37C, no diffusible brown pigment produced on culture and absence of conidia.
McGinnis (1980), Chandler et al. (1980), Rippon (1988), de Hoog et al. (2000, 2015), Ahmed et al. (2014b), Desnos-Olliver et al. (2006), Irinyi et al. (2015).