Glossary of Common Molds

This mold glossary is for information purposes only and is a basic overview of common molds we deal with in water damaged buildings and outdoor air samples. This glossary of common molds should not be used as any definitive source of reference. It is drawn from our 25 years of experience and thousands of hours looking into our microscopes. Most pictures are taken from our air and surface mold samples.

 
Chaetomium

Cladosporium

Stachybotrys

Penicillium / Aspergillus

Curvularia

Epicoccum

Memnoniella

Alternaria

Tetraploa

Trichoderma

Spegazzinia

Ulocladium

Hyphal Fragments

 

 

 

 

 

Chaetomium

This genus of mold is commonly found growing in damp buildings, usually on drywall, paper or wood surfaces. Chaetomium is relatively slow growing and requires very wet conditions, so its presence is an indication of extended or repeated wetting of materials. The genus includes species that are known to be toxigenic and allergenic, as well as some that are known opportunistic human pathogens.

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Cladosporium

This genus is the most common mold in the outside air. Cladosporium can also grow inside damp buildings and is often found on shower and window surfaces (usually feeding on a soap/soil film), and in and around HVAC ducts and vents. Many mold species of Cladosporium are known to be allergenic. Some may be toxigenic mold.

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Stachybotrys

This genus of mold is often found growing in damp buildings, usually on drywall, paper or wood surfaces. It is relatively slow growing, so its presence is an indication of extended or repeated wetting of materials. It requires high moisture levels. Stachybotrys is widely recognized as one of the more problematic organisms to have growing inside a building. It produces a number of mycotoxins under the right conditions.

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Air Sample

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Surface Sample Click to Zoom


Penicillium / Aspergillus

This group of organisms is composed of the Penicillium genus (>200 species), the Aspergillus genus (>200 species), and some other less common genera. Their common feature is the small round nature of their spores, making differentiation by species (speciation) difficult with non-viable analysis methods. Accurate speciation generally involves the use of culturable methods, which require extended time to receive results. The Penicillium/Aspergillus group is common outside, and is the group most frequently found growing inside damp buildings. It is a highly diverse group that can digest a wide variety of materials and thrive over a wide range of temperature and moisture levels. It includes organisms that are known to be toxigenic and allergenic, as well as some that are known opportunistic human pathogens.

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Curvularia

This genus is typically found as plant debris and in the soil of tropical or subtropical plants. Curvularia is a fairly common mold in the outside air. It can also grow inside damp buildings and is often usually found on wood products. Many mold species of this genus are known to be allergenic.

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Epicoccum

This genus is widely distributed and commonly isolated from air, plant debris, soil and foodstuff. It is found also in some animals and textiles. It is typically disseminated as a dry spore through wind. There are no documented cases of infection in humans or animals. Epicoccum grows rapidly and produces woolly to cottony or velvety colonies on potato dextrose agar at 25°C. Common allergic reactions are typical of Type I allergies (hay fever, asthma).

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Memnoniella

This species is an indoor mold very closely related to Stachybotrys. The major morphological difference between the two fungi is that the conidia (spores) in Memnoniella are in long persistent chains whereas Stachybotrys spores are aggregated in slimy heads. Memnoniella has a world-wide distribution and is mainly isolated from soil, plants, and trees. Similar to Stachybotrys, it is isolated from cellulose-containing materials such as paper, wallpaper, textiles, and dead plant material. Sometimes both Memnoniella and Stachybotrys occur on the same water-damaged building material. Memnoniella mycotoxins could have toxicity similar to that of some isolates of Stachybotrys. Memnoniella is a dry spore that is easily distributed by the wind and is found on many surfaces.

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Alternaria

This group is comprised of up to 50 species and is found in most outdoor environments. Alternaria thrives on damp soil, dead organic debris and food stuffs. It is a known plant pathogen. Spores are spread on the wind when the colonies dry out. It can be found in damp indoor environments with a moderately high water activity requirement of 0.85- to 0.88 Aw. It is known to be allergenic and has been implicated in cases of pneumonia in sensitive individuals.

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Tetraploa

This species comprises a very small proportion of the fungal biota. This genus is naturally found just above the soil on the bases of leaves and stems of many kinds of plants and trees. Spores have very distinctive morphology. This genus is not typically found growing in indoor environments. Consequently, cases of human infection are extremely rare, but have involved cases of keratitis and subcutaneous infection of the knee. Allergenicity has not been studied. No information is available regarding other health effects or toxicity.

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Trichoderma

This ubiquitous species is a filamentous fungus that is widely found in soil, decaying wood, grains, citrus fruit, tomatoes, sweet potatoes, paper, textiles, and damp wood. Although it is commonly considered as a contaminant, Trichoderma may cause infections in presence of certain predisposing factors. It is considered an emerging opportunistic pathogen in immunocompromised persons. Very few human cases due to Trichoderma have been identified. Trichoderma infections have developed in immunocompromised patients and transplant recipients, as well as patients with chronic renal failure, chronic lung disease, or amyloidosis. Trichoderma is disseminated as a wet spore typically dispersed via rain, insects, water splash, and wind when dried out. Allergens are typically identified as Type I (hay fever, asthma) or Type III (hypersensitivity pneumonitis).

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Spegazzinia

This species comprises a very small proportion of the fungal biota. This mold spore naturally inhabits soil, trees, and plants, and has never been identified growing in indoor environments. No information is available regarding health effects or toxicity. Allergenicity has not been studied. This species is usually identified on spore trap samples, though may be found in culturable (Andersen) samples if incubation period is sufficient to allow sporulation to occur. Spores of this species are clearly identifiable due to their distinctive morphology.

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Ulocladium

This ubiquitous species is widely found in soil, dung, grasses, paint, fibers, wood, decaying plant material, paper, and textiles. It is normally disseminated as a dry spore in wind. Commonly found indoors on gypsum board, tapestries, jute carpet backing, paper, and paint. Ulocladium has a high water requirement. Spores may cause subcutaneous tissue infections, though very rarely. Allergens may be severe in some individuals and reactions are typically identified as Type I (hay fever, asthma). Ulocladium may cross-react with Alternaria, adding to the allergenic burden of Alternaria-sensitive patients.

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Hyphal Fragments

The basic "stem" of the plant-like structure. Many fungi do not adapt well to routine lab media and sterile (unnatural) growth conditions and may not sporulate. Specialized media, light-dark cycles, UV light, and low or high temperatures may be required to stimulate sporulation. Unless distinctive spore types are formed, identification may not be possible. Frequently non-sporulating colonies are produced by basidiomycetes (mushrooms) which usually do not produce fruiting structures on lab media.

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Common non-biological components of air samples
Candle Soot Cloth Fibers

For additional inforamtion on individual mold species and genera, please visit http://www.emlab.com/app/fungi/Fungi.po

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