Mucor amphibiorum

About Mucor amphibiorum

Mucor amphibiorum belongs to the Mucorales, a group of fast-growing, water-loving fungi that thrive under high-moisture conditions. Elevated indoor Mucor levels are generally associated with materials that have been wet, for example after flooding, a plumbing leak or heavy condensation. Mucor and related genera (Rhizopus) can cause mucormycosis, a rare but life-threatening fungal infection that can invade blood vessels and cause tissue death, particularly in individuals with diabetes, organ transplants, or blood cancers. Whether the values in this sample are clinically relevant to any specific person is a question for a qualified clinician.

Ecology and water requirements

Mucor amphibiorum is classified as a tertiary colonizer in the ecological succession that follows water damage in indoor environments. Primary colonizers (xerophilic Penicillium and Aspergillus species) establish first on damp materials at relatively low water activity; secondary colonizers (Cladosporium) follow as moisture stabilizes; tertiary species like Mucor amphibiorum require sustained, high water activity (A_w 0.93 or above)^[2] and typically appear after weeks to months of continuous wetness. Because of this requirement, its detection in indoor dust samples is one of the more diagnostic available signals of significant, sustained water intrusion^[3], distinct from elevated humidity alone. The species cannot establish on materials that dry between wetting events; persistent water contact with cellulose-containing or other organic substrates is required.

Mycotoxin biology

Mucor amphibiorum is not currently documented as a significant mycotoxin producer in the indoor environment context. Its primary health relevance indoors is generally as an allergen. Fungal spores and hyphal fragments are documented triggers for allergic rhinitis, asthma exacerbation, and hypersensitivity reactions in sensitized individuals. Allergen production and inflammatory potential vary by strain, growth substrate, and environmental conditions. As with all ERMI species, a positive DNA detection in dust indicates that spore material is present in the home but does not directly measure airborne exposure or sensitization status.

Detection in dust versus visual inspection

DNA-based detection of Mucor amphibiorum in settled household dust (the basis of the ERMI panel^[1]) integrates spore material from current and recent growth in the home, capturing exposure history over weeks to months. A positive detection in dust does not necessarily indicate currently-active growth at the time of sampling; conversely, an active growth site can produce relatively low dust spore counts if the spores are not being aerosolized (sealed wall cavities, behind vapor barriers, or under flooring). Interpretation requires considering the dust signal alongside building inspection, occupant symptom history, and the broader pattern of species detected on the panel.

Where it’s typically found

Mucor amphibiorum is documented on the following substrates and locations:

• Wet or flooded building materials
• soil
• decaying organic matter
• compost
• damp food storage areas

Mycotoxins

No mycotoxins documented for this species in our reference literature.

On your ERMI report

Mucor amphibiorum is one of the 10 EPA environmental reference species used to compute the SLG2 component of the ERMI score (sometimes labeled "Group 2" in EPA documentation). Group 2 species are commonly found in outdoor air; their levels are subtracted from the indicator-species sum, which means high outdoor-reference detections actually reduce the final ERMI. A low-level detection of Mucor amphibiorum is common, because these species are also found in outdoor air. Our interpretation report reads its level alongside the indicator species.

Related species