Molds of the genus Mucor are found in soil and as saprobes of plants and manure in the wild, and as a common contaminant of stored and processed foods in the kitchen. There are about 50 species described worldwide and many plague water-damaged or moist structural materials and can inflict allergies on exposed people.

View a second image of a Mucor zygotes.

As a member of the phylum Zygomycota, the filamentous fungus grows rapidly at 25 to 30 degrees Celsius, sometimes several centimeters high, and at the macroscopic level, its fluffy appearance resembles cotton candy. Initially the mold is white and gradually becomes gray with maturity. The life cycle is complex and involves asexual and sexual reproductive methods. Zygospores, if present, arise from the mycelium. Species of Mucor are distinguished from one another by the branching (unbranched or branched), the presence of sporangiophores and their shape (oval or round), the maximum temperature tolerated for growth, the presence of chlamydospores, and whether or not they can assimilate ethanol. The other genera of zygomycots grow best above 40 degrees Celsius, significantly higher than the maximum of 37 degrees reported for Mucor species.

Species in the fungal genus can cause a group of infections in humans known as zygomycosis. Zygomycosis includes infections in mucous membranes, nasal passages and sinuses, eyes, lungs, skin, and brain, as well as renal and pulmonary infections and septic arthritis. People suffering from diabetes, extensive burns, immunosuppression symptoms associated with AIDS and other afflictions, or those who are intravenous drug users, appear to be most susceptible to Mucor infections. Treatments of Mucor and other fungal infections of the phylum Zygomycota are difficult because of their property of invading vascular tissues of immuno-suppressed people, and mortality rates are relatively high.