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This article defines mold hyphae or hyphal fragments and then discusses the significance of hyphal fragments as an indicator of mold contamination in a building and how we can find evidence suggesting that a given mold contamination case is new, old, or includes both old and new fungal growth.
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Useful Lay-person Definitions of Hyphae and Fungal Hyphal Fragments
The Dictionary of the Fungi defines hyphae as
hypha (pl. hyphae), one of the filaments of a mycelium;
At MOLD ATLAS & PARTICLES INDEX we offer our own longer definition of fungal hyphae or hyphal fragments found in mold samples and mentioned in mold lab reports:
But their presence in indoor air samples, if in quantity or in large segments, suggests an active fungal colony in the building. Their presence in a surface sample in quantity or in large segments indicates that active fungal growth is present or nearby, or that fungal material has been disturbed in the building. May be allergenic. -DF
Hyphal fragments might be just one or two little bits or a rats nest of growing mycelia (as we show at page top).
Hyphal fragments or hyphae may be colored (brown for example shown at the top of this page and just above) or colorless as in our photograph below (mycologists report colorless spores or hyphae as hyaline - just in case your report is not written in plain english).
Of course this means we need another definition right away.
Mycelia would not easily be visually identifiable as belonging to a specific species unless other components of the fungus are present. Particles of this material are probably allergenic. - DF; derived from op cit.
Mycelial cord, a discrete filamentous aggregation of hyphae which, in contrast to a rhizomorph, has no apical meristem; syrrota; - op cit.
What is the Biological Job of a Mycelium or of Hyphae?
From a lay person's view, it's reasonable to think of hyphal fragments as little pieces of plant stems or roots - except in this case the organism is not a tree or bush, but a fungal structure - mold.
When you see a mushroom sprouting in the forest, that's the fruiting body of what can be a very large, but hidden root structure underground - a mycelium. From the fungi's point of view, the mycelium is the "stomach" of the organism.
A mycelium exudes chemicals that help dissolve food that it is contacting, such as a leaf, or a piece of wood or paper. Nutrients are dissolved and transported into the mycelial structure.
A mycelium grows, that is, gets bigger, from the tips of individual hyphae.
What is the Significance of Hyphal Fragments Reported in a Mold Lab Test Report?
It is normal to find a few hyphal fragments in outdoor air and thus also in indoor air. At high levels or in some circumstances, these particles might tell us something more about the building in which they were detected. But if just a few such particles are reported in a mold lab report, they are most likely insignificant.
In some fungi hyphal fragments may be allergenic or may even contain mycotoxins. (In our terminology, fungal material may be harmless-cosmetic, allergenic, toxic, or pathogenic, depending on the genera/species and on its growth conditions.)
But the hyphal fragments or pieces found in air or dust samples are usually quite large and not likely to be inhaled deeply into the lungs. So mold hyphal fragments are less of an airborne risk to building occupants than say a high level of airborne toxic or allergenic mold spores such as Aspergillus sp.
We report hyphal fragments in air or dust samples (where it is common to find at least some) for these reasons:
Does the Presence of Hyphal Fragments Indoors Threaten New Mold Growth?
While some hyphal fragments might, if conditions were ripe, begin growing and eventually also lead to mold spore production, that's not really a critical focus. In our opinion, if conditions are ripe to grow mold, you'll get mold growing whether there were previously some hyphal fragments there or not.
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