Mucor is a genus of about 40 species of molds commonly found in soil and on plant surfaces, as well as in rotten vegetable matter.
Colonies of this fungal genus are typically white to beige or gray and fast-growing. Colonies on culture medium may grow to several centimeters in height. Older colonies become grey to brown in colour due to the development of spores.
Mucor sporangiophores can be simple or branched and form apical, globular sporangia that are supported and elevated by a column-shaped columella. Mucor species can be differentiated from molds of the genera Absidia, Rhizomucor, and Rhizopus by the shape and insertion of the columella, and the lack of stolons and rhizoids. Some Mucor species produce chlamydospores.
During asexual reproduction, erect hyphal sporangiophores are formed. The tip of the sporangiophore swells to form a globose sporangium that contains uninucleate, haploid sporangiospores. An extension of the sporangiophore called the columella protrudes into the sporangium. The sporangium walls are easily ruptured to release the spores, which germinate readily to form a new mycelium on appropriate substrates.
During sexual reproduction, compatible strains form short, specialized hyphae called gametangia. At the point where two complementary gametangia fuse, a thick-walled, sphaerical zygosporangium develops. The zygosporangium typically contains a single zygospore. Nuclear karyogamy and meiosis (sexual recombination) occur within the zygospores, which are thought to be long-lived and resistant to adverse conditions. They may germinate to form hyphae or a sporangium. Mucor includes both homothallic (self-compatible) and heterothallic species.
Most species of Mucor are unable to infect humans and endothermic animals due to their inability to grow in warm environments close to 37 degrees Celsius. Thermotolerant species such as Mucor indicus sometimes cause opportunistic, and often rapidly spreading, necrotizing infections known as zygomycosis.
- Mucormycosis (a rare infection caused by the sole member of a different genus of the Mucoraceae family, Apophysomyces elegans).