Environmental Engineering Reference
In-Depth Information
Figure 6.6
Stachybotrys
spores/spore-bearing structures. (Courtesy of University of
Minnesota.)
needs from nonliving organic matter. Most saprobes are saprophytes, that
is, they decompose dead plant matter. Some species are both parasitic and
saprobic, living on dead organic matter but invading living tissues when a
host is present.
Most parasitic fungi are plant pathogens. A number of these are notable
because they pose major threats to agricultural crops, which require contin-
ued selective breeding programs or intensive use of fungicides for their
protection. A small number of species can parasitize humans, causing infec-
tions of the skin (e.g., athlete's foot) or more serious diseases such as histo-
plasmosis and life-threatening pulmonary infections (aspergillosis).
The major ecological role of fungi is decomposition, a role shared with
bacteria and insect larvae. During decomposition, fungal hyphae infest sub-
strates, producing extracellular enzymes that digest complex organic mole-
cules into smaller and simpler molecules that are absorbed and metabolized.
Decomposition is a successional phenomenon, with different species domi-
nating as the decomposing substrate changes. As a consequence, substrate
samples often show the presence of a number of species.
Fungal species have varied growth requirements. Therefore, individual
species may be prevalent on some substrates and in certain environments
but not others. These growth requirements affect species prevalence in both
outdoor and indoor environments.
Many saprobic fungi can use a variety of substrates. Substrate coloniza-
tion in individual situations is dependent on their ability to compete with
other species, as well as the presence of suitable temperatures and availabil-
ity of water.
D. Environmental requirements
Water is a major limiting factor in the growth of fungi. Humidity >70% is
required for spores to germinate, and optimal substrate moisture is necessary
 
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