Mucor is a fungal genus within the Zygomycetes class of fungi that contains an estimated 40 species. Members of the genus can be found living all over the world, in a wide variety of environments, from the forest to the carpets of homes and businesses. In Northern Europe especially, these species are ubiquitous indoors, and they can contribute to mold allergies in sensitive individuals. Some species cause diseases in humans, while others are known plant pathogens.
Fungi in this genus grow in the form of a white to gray mold that develops into a fluffy mass. The mold can grow on living and dead plants and in the soil. Mucor species are very aggressive, and they will quickly overrun an environment and dominate other fungi. The mold grows and spreads quickly, making it difficult for slower-growing fungi to compete. Like other members of the class Zygomycetes, these fungi can reproduce asexually with spores, or sexually by fusing to create zygospores which contain a mixture of genetic material.
On magnification, fungi in this genus appear in the shape of very fine threads topped with ball-shaped clusters of spores. When they dry out, the balls rupture, allowing the spores to spread through the natural environment. Spores can also be spread through running and seeping water, which is one of the reasons why these species can be such a problem in structures, as the spores will hitch a ride along leaks and seeps in walls. To eliminate the fungus, it is necessary to use soap, followed by a bleach rinse, to remove it, and to dry the environment thoroughly to inhibit the spread of spores and the growth of the mold.
Some species have been linked with allergies and mold sensitivity. In some cases, they can cause severe pulmonary distress, including difficulty breathing, and in immunocompromised individuals, the fungi can cause opportunistic infections. These occur when the spores are ingested or inhaled, and the mold can quickly spread through the body, causing a variety of health problems. Antifungal medications can be used to treat Mucor infection, although some species can be very stubborn.
Many species cannot tolerate human body temperature. Only a handful of species are heat-tolerant enough to survive in the human body, which may explain why the genus does not cause more infections. One species, M. piriformis, is famous for causing Mucor rot, a disease in plants, and several species produce enzymes that can be used in cheesemaking, illustrating the diversity of this fungal genus.