MUCORACEM 



973 



The sporangial protoplasm not used in the formation of endo- 

 spores gives rise to a peculiar mucilaginous substance, which at a 

 later period, by absorption of water, causes the bursting of the 

 sporangium. Each endospore or gonidium, when it has become 

 free, gives rise to a mycelial tube by germination. This mycelial 

 tube ramifies, and a new mycelium is formed. 



In some species, under certain conditions, a sexual reproduction 

 may take place. This consists in the conjugation of undifferentiated 

 non-motile gametes, which leads to the formation of zygospores. 



Many species, when vegetating in unfavourable media, reproduce 

 only by formation of conidia and chlamydospores. 



The Mucoracese are extremely common as parasites or saprophytes 

 of plants and animals. A mycosis due to these parasites is often 

 termed ' mucormycosis.' 



Mucoracese can be easily grown on sugar culture media — for 

 instance, Sabouraud's maltose agar — or even on ordinary agar. 

 The optimum temperature for their growth is between 35° and 

 40° C. The Mucoracese require plenty of oxygen, and therefore 

 the media tubes must never be closed with rubber caps. When 

 there is not enough oxygen, the Mucoraceae lose their character- 

 istics, and give rise to monilia-like or yeast-like forms. 



Classification. — Four genera of Mucoracese are found to contain 

 species parasitic on man: — 



Mycelium ramified, no rhizoidS' — Mucor. 



Mycelium non-ramified, with or without rhizoids; the peduncle 

 Family supporting the sporangium terminates in a special forma- 



Mucoraceae tion encircling the base of the columella — Lichtheimia. 



Mycelium with rhizoids; columella ovoid' — Rhizomucor. 

 Mycelium with rhizoids; columella hemispheric, shaped like a 

 mu^Yiroomr—Rhizopus. 



Genus Mucor MicheH, 1729. 

 Ramified mycelium ; absence of rhizoids. 



Mucor mucedo Linnaeus, 1764. 



Synonyms. — Mucor vulgaris Micheli, 1729; M. sphcerocephalus 

 Bulliard, 1791. 



The hyphse carrying sporangia (sporangiophores) are long and 

 erect; the sporangium is globular, 100 to 200 in diameter; its 

 colour brownish; its surface covered b}^ fine, minute crj^stals of 

 oxalate of calcium. The spores (gonidia) are elliptical, with a 

 smooth surface. The columella is ovoid-shaped, and generally 

 yellowish. Occasionally very large zygospores may be observed. 



M. mucedo L. is very common, living in organic substances in 

 decomposition — for instance, horse-dung. It is the cause of a 

 deadly disease in bees — the so-called ' mucorine,' or May's disease- 

 but is seldom found in man. Fiirbringer has observed it twice in 

 cases of pulmonary infarcts. A case of broncho-pulmonary mucor- 

 mycosis has been observed by Castellani in the Balcanic Zone. 



