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This document is also available as a PDF. WHERE MOULDS ARE FOUND Almost any natural material, no matter how small, will support an indigenous population of moulds.
Moulds are part of the economy of nature, quickly occupying dead or nearly dead materials and returning
them to the basic building components of new organisms. As such, they are essential to what biologists
call nutrient cycling, the process whereby nutrients never leave the realm of living things, but simply get
used again and again; earth to earth, ashes to ashes, dust to dust. While acknowledging that moulds are everywhere, it is useful to classify their habitats into a number of
categories based on nutritional characteristics. Moulds have specialized nutritional requirements and
usually do not range very far from their usual habitats: fungi that naturally decay seaweed on the beach
will not be expected to occur on mouldy bread in the kitchen. The competition among moulds having
similar nutritional requirements is intense and leaves no room for a mould adapted to another habitat. Aside from nutritional and competitive barriers, other factors encourage habitat restriction among
moulds. Most influential is spore dispersal. Although most moulds seem to produce astronomical
numbers of spores, they are, in fact, practising a strict economy. In their highly competitive life there can
be little waste; every minute bit of energy must be put to good use or a more efficient organism will
prevail. Thus moulds will produce only enough spores to ensure reproduction of their species from year
to year. If a mould were to put a disproportionate amount of energy into spore production, it would have
to be at the expense of some other activity, such as rapid growth. Economy in spore production is best
ensured by mechanisms of spore dispersal conferring a high probability of encountering suitable places to
germinate and grow. Many different mechanisms exist and account for the great variety of spores and
spore-producing structures found in moulds. In many instances, moulds living together in particular habitats have similar methods of spore dispersal,
even when the moulds themselves are not closely related, illustrating the idea that many structures in
organisms are similar because of common ecological pressures rather than common ancestry. Thus we
come again to a basis for subdividing habitats, and, as we shall see later, also a basis for applying certain
techniques for the isolation and cultivation of moulds. Living plants 1 of 11 9/30/99 11:50 AM Source http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds/Source.html Most plant diseases are caused by fungi. The largest
group of plant parasites are the rusts, a highly specialized
group of organisms that grow extremely slowly in the
laboratory and are outside the usual definition of moulds.
Powdery mildews, like the colonies of Uncinula
circinatum parasitzing a maple leaf at right, have never
been cultivated away from their plant hosts. Some plant
disease fungi are less difficult to grow but are so
specialized as parasites that they seldom occur in
laboratories other than those of the plant pathologist.
Many of these fungi have rather strict nutritional
requirements to induce sporulation and are usually seen
in cultivation only as sterile hyphae. The plant disease fungi most commonly encountered as
moulds are those having non-parasitic stages in their
life-cycles. These fungi usually grow and sporulate well
in the laboratory. Examples are species of Phoma,
Fusarium, Bipolaris, Graphium, Pestalotiopsis, and
Monilia. Most parasitic fungi do not produce great numbers of
spores and it is likely that they are transferred to
uninfected plants by fairly specific means. Those having wet spore stages, such as species of Phoma,
Fusarium, Pestalotiopsis, and Ustilago (a smut), are probably transmitted by insects or other arthopods,
such as mites. Other fungi, such as Cladosporium and Monilia, produce large numbers of dry spores, and
appear to be wind-dispersed. Also conspicuous are fungi attacking plants weakened by senescence or disease. Such invaders are hardly
parasites in the strict sense. Many of these fungi are now considered to be "endophytes", organisms that
enter plant tissues while they are still healthy and remain there in a dormant state until the tissue is
weakened or dies. Some ecologists now view these endophytes not as parasites but as the first arrivals in
a long sucession of decay organisms. Many species of Alternaria, Botrytis, Cladosporium, Fusarium, and
Ulocladium may belong here. Dead plant material Herbaceous plants Moulds occurring on dead herbaceous plants are often the same species attacking dying ones. Thus we
can again list Alternaria, Cladosporium, and others, as well as a few new ones such as Epicoccum and
Candida. In temperate climates, where many plants die in the fall, there is a tremendous flush of mould
activity in autumn. Because the dead plant material is so abundant, finely tuned dispersal mechanisms are
not necessary and the moulds simply release their spores in the wind. The likelihood that a spore of
Cladosporium, for example, will hit a dead plant part in the autumn is very great. Nutritional specialization dictates that different plants will support different fungi, and we find, for
example, dead grasses yielding a different flora of moulds than dead milkweeds or mustard, at least to a 2 of 11 9/30/99 11:50 AM Source http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds/Source.html partial extent. Wood Dead wood is a good source of moulds and provides two distinct habitats, depending on whether it is
covered with bark or not. Moulds occurring under the bark of fallen and standing trees cannot disperse
their spores into the air and most often utilize insects and mites for their transmission. Although, as we
might expect, many have wet spores ideal for sticking to the bodies of their dispersers, some have dry
spores that appear to become trapped among the animals' body hairs. I have seen hundreds of the curved,
dry ascospores of Fragosphaeria purpurea trapped among the bristles on the backs of mites under bark
of maple trees in Ontario. Often the moulds under the bark of dead standing trees are different from those
on fallen trees. The surface of wood not covered with bark often has a distinct community of moulds. Although air
dispersal of spores is possible in this situation and apparently often occurs, wet-spored moulds are still
abundant. Again standing and fallen trees support different fungi. Freshly cut wood is a good source of
moulds causing a phenomenon called blue stain. These moulds, common in lumber-yards as bluish to
black discoloration on the wood, produce tall sporulating structures bearing wet drops of
insect-transmitted spores. Closely related species occupy the tunnels and galleries formed by beetles
under the bark of living and recently dead trees. Leaves Dead or dying leaves of trees support moulds similar to those from herbaceous plants, with some notable
exceptions. However, tree leaves appear to support fewer Alternaria and Cladosporium colonies, thus
often allowing a better chance to observe the more slowly growing or rarer fungi. For example, in
Ontario fallen leaves of ash support a pin-sized mushroom called Marasmius minutus, that never occurs
on herbaceous plants. Leaves submerged in water support a number of moulds with unusual spore forms. The spores may be
needle-like, coiled like a watch-spring, or coiled into barrel-shaped structures that bob to the surface of
the water and float away. Others have three or four narrow arms and look something like jacks with two
or three of the arms missing. These moulds may be examined by submerging leaves in a bowl of water
and stirring them vigorously. After a few minutes the spores will float to the surface, where they can be
skimmed off in a drop of water. Best results are obtained with leaves likely to become submerged later in
the natural habitat but have not yet become so. Animals and humans Diseases A number of diseases of humans and animals are caused by mould and yeast-like fungi (Figure 7). Many
are known only from this habitat and are quite specialized. Notable are the moulds called dermatophytes,
the cause of a number of skin diseases such as ringworm and athletes' foot. The fungus grows on the
outermost layer of skin, causing reddening of the surrounding tissues (zoophilic types) and sometimes
scaliness (anthropophilic types). Dermatophytes do not normally attack deeper tissues; the symptoms are
usually due to an allergic reaction. Because of their essentially non-parasitic nature dermatophytes are 3 of 11 9/30/99 11:50 AM Source http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds/Source.html usually easy to grow in the laboratory. Many closely related species occur on substances similar to human
skin, such as leather, feathers, hair, and horn, and are unable to grow on living animals or man. Probably
the most commonly isolated dermatophytes are species of Microsporum (Figure 7A), Trichophyton, and
Epidermophyton. Several fungi can occur on living tissues and cause serious disease and even death. Many such organisms
are known only from individuals who have low disease resistance, due to prior infection, AIDS, old age,
or other factors. Most commonly, infections by these fungi occur when the normal bacterial populations
of the body are eliminated by the use of antibiotics. Without competition from bacteria these fungi occupy
the tissues and grow rapidly, often causing considerable damage. Other fungi attack healthy living tissues without the aid of antibiotics, causing more localized but very
serious infections. Histoplasmosis, a disease with symptoms similar to those of tuberculosis, is caused by
Histoplasma capsulatum, a mould associated with bird nests in nature (Figure 7C). It is frequently
reported in perfectly healthy people who have been exposed to the dust from nesting materials, such as
while tearing down old barns. The study of medically important fungi is beyond the scope of this book and will not be discussed further.
There are several good books dealing with medical fungi from a mycological (rather than medical) point
of view. Especially useful are Hoog and Guarro, 1995; McGinnis (1980) and St-Germain and
Summerbell, 1996. Figure 7. Some fungi of medical importance. A: Microsporum, causative agent of ringworm and other
skin diseases. B: Blastomyces dermatidis, causative agent of North American blastomycosis. C:
Histoplasma capsulatum, causative agent of histoplasmosis. Predation 4 of 11 9/30/99 11:50 AM Source http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds/Source.html Some moulds actually trap small (usually microscopic) animals. Best known are those that trap eelworms
or nematodes (see Barron [1977] for an excellent account of these fungi). The traps produced by these
fungi are composed of loops, networks of filaments, or knobs and branches. Some are reminiscent of the
well known Venus' fly-trap, and are sprung upon contact with an eelworm. When the worm crawls into a
ring of one of these fungi, the ring rapidly constricts, holding the eelworm tightly. At first the worm
struggles violently, but it soon becomes still and is invaded by the filaments of the mould. In other
species, the loops and branches are sticky and hold the eelworm fast as soon as it touches them. A second group of eelworm catchers produces spores that are swallowed by the worm, germinating later
in the gullet. At least one species has an elaborate injection mechanism that, when sprung, forces a small
portion of the spore right into the tissues of the side of the eelworm. Soil Soil is one of the most commonly studied mould habitats. It is source of plant disease fungi, some human
disease fungi, predacious fungi, and a host of forms that bring about the transformation of dead plant and
animal material into soil. Soil is not a uniform substance; in fact, it is so complex that a study of soil is a science in itself. Scientists
recognize several layers in the soil, starting at the surface and working down. These are: L layer: the layer at the soil surface composed of undecayed plant litter. The origin of the litter is clearly
identifiable. F layer: the layer with identifiable but partially shredded or decayed plant material. H layer: the layer containing much material of plant origin, but with individual structures no longer
recognizable. A layer: the layer with plant or organic matter present but unrecognizable as such or well mixed with
loam (a mixture of sand, silt, and clay). B layer: a mineral layer containing little organic matter. C layer: the parent rock from which the mineral layer is derived. Naturally these layers are not always distinct, and grade more or less evenly on into the other. Some soils,
especially agricultural ones, lack stratification altogether. Soils differ from one another in the kind of plant
material falling into them; the relative proportions of sand, silt, and clay in the mineral components; the
moisture content; the relative acidity or alkalinity (pH); and in many other characteristics. Fungi, because they are highly specialized users of organic substances, vary from one soil to another and
with depth in the same soil. They are entirely dependent upon the kind of material falling into the soil: a
fungus specializing in oak leaves will probably not colonize a pine needle. This factor alone will account
for many differences between the mould populations of two soils. In addition fungi may be sensitive to
moisture levels, pH, competition from other organisms, and many other influences. 5 of 11 9/30/99 11:50 AM Source http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds/Source.html As a leaf falls into the soil it is shredded by arthropods and digested by microorganisms. Gradually it
becomes buried under newer generations of leaves and thus moves down into the lower layers of soil. It
undergoes continuous decay by moulds, bacteria and other organisms until it finally disappears
(somewhere in the B layer). Fungi that first invade the leaf, often while it is still on the tree, will grow on
it until the particular nutrient they need is exhausted and then die back, to be replaced by new fungi
extracting what they need from the leaf. In this way, a leaf moving down through the layers of soil will
have a series of moulds on it, each replacing a previous population. This transition of populations as the
habitat ages and is modified is called succession and is the object of much study and discussion among
ecologists. Although we tend to think of soil fungi as decomposers of litter, they play a number of other roles as
well. Many are associated with animals and animal products and may trap eelworms and other soil
animals, or decay the dead bodies of insects and earthworms. Some invade cast-off feathers and hair, and
at least one group specializes in old hooves and horns. Through their roots, living plants offer an attractive habitat for soil-inhabiting fungi. Some live around the
root and decay away the dead root layers or substances exuded by the root. Others invade the living root
tissues and either cause plant disease or live in harmony with them. The latter situation involves a form of
symbiosis called mycorrhizae, where the root and the fungi within each benefit the other, In fact, most
mycorrhizal fungi and plants cannot live apart. Only a few species of plants are consistently free of this
association. Air Air, of course, is not a habitat for moulds, though many disperse their spores by air currents and are
encountered in routine work. Fungi have a variety of mechanisms for getting their spores into the air. Simplest is that of exposing dry
spore masses to air currents. Many moulds use this method, especially those that colonize exposed leaves
and stems. Species of Alternaria, Cladosporium, and some of the basidiomycetes called smuts are
conspicuous for this kind of dispersal. These species usually produce large numbers of spores, a necessary
expenditure if at least a few randomly dispersed spores are to land on a suitable place to grow. Ascomycetes and basidiomycetes are usually capable of shooting their spores away into the air. Asci are
like popguns: the water pressure inside the ascus builds up higher and higher until the spores are fired out
the end with considerable velocity. Ascospores can, in fact, be shot a distance of several centimetres from
the end of the ascus, a prodigious feat considering the microscopic size of these mechanisms. The
equivalent at our own scale would be to fire a 30-cm projectile a distance of 6 km, a feat necessitating a
105-mm howitzer! With such a mechanism, ascomycetes need not be exposed directly to the wind but
may grow in places allowing entry to the air of their discharged spores. Thus ascomycetes are often found
growing closer to the ground than other air-dispersed organisms. Basidia discharge their spores from the tips of small projections called sterigmata. Such spores,
sometimes called ballistospores, are not shot very far, only far enough to clear the surface of the
basidium and the fruiting structure. The fruiting structures of basidiomycetes may be microscopic in size
and bear only a few basidia or they may be very large, as in mushrooms and bracket fungi. These last
fungi often continue to produce spores throughout the growing season and can produce a staggering 6 of 11 9/30/99 11:50 AM Source http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds/Source.html number. One of the most prolific of these, the "artist's fungus", Ganoderma applanatum, may disperse its
airborne spores many kilometres from the woods where it grows. Related to the basidiomycetes are the
mirror yeasts, a group of yeasts that produce ballistospores on solitary sterigmata. Most basidiomycetes
are not normally encountered as moulds, and are really outside our interest here, but a few, such as
Sistotrema brinkmanii may be encountered in the laboratory. Some spores become airborne by a mechanism known as droplet adhesion, a process dependent upon the
presence of tiny water droplets in the air. When one of these droplets, as on a foggy day, encounters a
mould spore attached to a leaf, for example, the spore adheres to the droplet by surface tension and is
carried off on it. It is then either deposited when the drop comes to earth, or becomes truly airborne when
the drop dries out. There are a few other mechanisms whereby spores become airborne, but these are rather more specific to
one or a few species. Most are forcible discharge mechanisms and may involve various kinds of spring,
water jet, or bellows devices. A discussion of these and other common mechanisms is found in the
excellent book on dispersal in fungi by C.T. Ingold (1953). Dung Although people expect dung to be a rather disgusting material to study, many become so intrigued with
the moulds and other organisms found there that they soon overcome their initial objections. Many fungi found on dung are highly specialized for growth there and never occur anywhere else. They
do not produce large numbers of spores and thus require a high probability of success in getting their
spores from one dung pile to another. The most commonly cited life-cycle in dung-inhabiting or coprophilous fungi is that shown by many
ascomycetes. The spores of these ascomycetes are very heavy, sticky, and dark, and when they are shot
from the ascus their weight allow them to travel a relatively great distance. Because of this weight,
however, they do not usually remain in the air long, but follow a parabolic trajectory and land near the
dung pile. Because they are sticky, often with rather elaborate slimy coverings or tails, they adhere to
whatever they fall on, and because of their dark colours they are not greatly affected by the ultraviolet
radiation in the sunlight to which they are exposed for an often considerable length of time. Eventually
they may be eaten, if they have fallen on vegetation, by a grazing animal, ultimately to be packaged up in
a new pile of dung. Many of these spores have a dormancy mechanism that prevents them from
germinating on the vegetation but that can be broken when subjected to the processes of the animal's
digestive tract. Most coprophilous ascomycetes are light-sensitive and aim their spore shots away from
the dark-coloured dung, a first step in their journey to a new dropping. Other coprophilous moulds present their spores to the environment in wet drops at the ends of stalks.
When one of the many insects or mites attracted to dung brushes against these stalked spore drops they
carry with them a few of the sticky spores. Later, perhaps on a new dung pile, the spores rub off and
germinate to produce a new colony. Most insect-transmitted fungi lack dormancy mechanisms in their
spores, and are unlikely to be away from dung for more than a few hours. The variety of coprophilous fungi is large, and many occur in the laboratory as moulds. Included are
several kinds of ascomycetes, some small mushrooms, slime moulds, zygomycetes, and many anamorphs.
It is a particularly rewarding group for study by the beginning mycologist. 7 of 11 9/30/99 11:50 AM Source http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds/Source.html One warning must be issued. Dung may contain the eggs, larvae or adults of parasitic organisms. While
most of these are of danger only to the species of animal producing the dung, some are able to parasitize
humans. Because of this dung should never be handled with bare hands. Figure 8. Spores of some dung-inhabiting fungi. A: Trichodelitschia. B: Thelebolus. C: Podospora. D:
Preussia. E: Triangularia. F: Cercophora. G: Sordaria. H: Coprinus. The human environment Food Aside from their role in plant, animal, and human disease, many moulds enter directly into human affairs,
in either a harmful or beneficial way. On the plus side is the involvement of moulds in the greatest
contribution to medicine of all time, that of antibiotics. The discovery of penicillin by Sir Alexander
Fleming in 1928 probably resulted in the saving of more lives than all other medical discoveries combined.
Penicillin, a product of the common mould Penicillium chrysogenum, is still one of the safest and most
widely used of antibiotics, in spite of a more than fifty-year search for others. The foods we eat are as nutritional to many moulds as they are to us, a fact often put to use in the
preparation of food products. For example, several types of cheese, such as Roquefort, Danish blue,
Camembert, and Brie, owe their distinctive flavour to the presence of mould growing on them. If the
mould were absent, these cheese would not ripen properly. Yeasts, although not really moulds, are
among the most important fungi in food preparation. Their value, at least for some Saccharomyces
species, lies in their ability to produce carbon dioxide and grain alcohol. In wine-making, where the
production of alcohol is valued, yeast is added to the grape juice to bring this about. In bread-making, the
important product is carbon dioxide, which is necessary in the rising process, and, again, yeast is added to
the dough. In the production of beer, both alcohol and carbon dioxide, to produce carbonation, may be
necessary, although today the carbon dioxide may be added later artificially. In the Far East, a number of moulds are used in food preparation that remain unexploited in most of the
world. Among these are species of Aspergillus, Monascus, and Rhizopus, used to process various rice,
bean and soybean products. 8 of 11 9/30/99 11:50 AM Source http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds/Source.html To most of us, the negative aspects of moulds in foods are more noticeable than the positive. Few of us
have failed to notice the pink, black, and green moulds growing on bread or the green or blue-green
Penicillium rots of citrus fruits. Moulds are one of the reasons food manufacturers include preservatives
in their products. One of the most destructive activities of moulds in foodstuffs occurs in stored seeds and grains. Certain
species of Aspergillus, Penicillium, and Eurotium are able to grow under particularly dry conditions and
attack stored grains. To guard against this, the grain must be dried to very low moisture levels. Keeping
grains dry in the humid tropics is particularly difficult if not, at times, nearly impossible. Not only do such
fungi damage the grains or render them unpalatable, they may also excrete toxins that can cause illness or
even death. Most famous of these are the aflatoxins - produced by Aspergillus flavus and other moulds -
which are not only immediately toxic but are also known to be carcinogenic. Aspergillus flavus often
grows on peanuts and was first discovered in peanut feed given to turkeys in Great Britain. Some of the same species of Eurotium that attack stored grain commonly appear on the surface of jams,
jellies, and syrups. These very sugary substances tend to prevent water from entering the cells of most
fungi and thus create what amounts to a microbiological desert. Eurotium species, with their ability to
grow under dry conditions, are ideally suited to such habitats. Some products, such as prunes and dried
apricots, are so dry and so sugary that even Eurotium species are unable to cope with them. They still can
be decayed by certain specialized moulds, however. Probably the most remarkable to these is Xeromyces
bisporus, which cannot even grow at the sugar concentration used to grow Eurotium species. Laboratory
cultures of this species are rather difficult to establish and require very special conditions. Cellulose products Cellulose is probably the most abundant material of biological origin on the earth and is a prime source of
energy for many fungi. We have met some cellulose-decomposing fungi already in our discussion of
moulds inhabiting dead and dying plant parts, notably Alternaria, Cladosporium and Epicoccum. While
these fungi are common enough, there are several others that seem to become especially common on
man-made cellulose products, such as paper, cotton, cardboard, and wood products. Many mould
growths on paper and cotton are commonly called mildews, but this term really has little meaning. These
fungi are able to dissolve the cellulose fibres in cotton and paper and thus cause the materials to
disintegrate. The process is especially rapid under moist conditions, as occur in damp basements or in the
tropics. Many species of moulds are involved in cellulose decomposition, but none are more widespread
than species of the ascomycete genus Chaetomium. During the Second World War, countries fighting in
the South Pacific and Southeast Asian areas lost a great deal of equipment to these species. The resulting
increased interest in Chaetomium is reflected most notably in Ames's (1963) monograph on the
Chaetomiaceae, published by the United States Army. Sawdust contains many cellulose-utilizing moulds that may cause unwanted decomposition. Particularly
undesirable are members of a group of moulds able to grow at high temperatures (up to 60° C). The
growth of these moulds may actually cause the temperature of the sawdust to rise. Combined with
bacteria having an even higher temperature tolerance and natural chemical activities these moulds may
eventually lead to spontaneous combustion, a common cause of fire in lumber-yards. Other products Many other manufactured products are susceptible to mould attack. Painted walls, particularly in humid 9 of 11 9/30/99 11:50 AM Source http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds/Source.html places such as showers, can become overgrown by certain fungi, notably species of Phoma and
Exophiala. Wallpapers also serve as a source of nutrition for some moulds. Commonly cited are the
Scopulariopsis species which have been reported to grow on wallpapers containing arsenic pigments and
to release very poisonous gases. With modern wallpaper pigments, which contain no arsenic, this cannot
happen. Leather is mainly protein and serves as a convenient source of food for moulds. Some of the moulds that
occur here are related to the dermatophytes that attack the outer layer of human skin; others belong to
quite different groups. Some substances that seem to be entirely unlikely to support fungal growth may be found to be well
colonized by these organisms. Exophiala species, for example, are found in syrupy solutions of polyvinyl
alcohol. Cladosporium (Amorphotheca) resiniae often occurs on the surface of aircraft fuels in their
tanks and can damage jet engines. Penicillium ochrochloron can be found in electroplating solutions that
are extremely acid and contain very high levels of toxic copper salts. I was once involved in a search for
the organism responsible for decaying inflatable life-rafts periodically soaked in seawater. The culprit
eventually turned out to be a species of Aspergillus. Moulds in the indoor environment Increasing attention is becoming focused on fungi in indoor environments. Although most of the moulds
occurring in human environments occur indoors, the interior of buildings are themselves a special habitat.
It has long been known that indoor fungi cause allergies in sensitive persons, but only relatively recently
have indoor moulds been linked to other health problems. While allergy sufferers generally react to
substances in fungal spores, other health problems may be caused by voltile substances released by
moulds into the air. Virtually all buildings contain moulds, but some are mouldier than others. Indoor moulds can be
remarkably tolerant of dry conditions but none can live without some moisture. Excessively mouldy
buildings generally have a source of moisture leading to unusually heavy mould growth. The source of the
moisture may be a leaky basement, a dripping pipe, a roof in need of repair or some other fairly obvious
cause. In most cases the mould can be seen growing on walls or other materials in contact with the
moisture. Sometimes the moisture can occur inside walls and not be apparent. A common but not obvious
cause of moisture in cold climates is condensation inside north-facing walls. Severely mouldy buildings
may have a musty smell, but not necessarily. Sometimes the only sign of a problem is persistant poor
health of the occupants, such as headaches, nausea, respiratory symptoms, etc. It is now known that
mouldy buildings can present a serious health risk to occupants. In fact, some infant deaths have been
convincingly linked to indoor moulds. Any building with an apparent mould problem should be
thoroughly investigated by qualified people. Not all indoor moulds present a risk to human health, but an abundance of any mould is likely to be
accompanied by others, including toxic ones. Species of Stachybotrys are particularly toxic. Obvious
occurrences of Stachybotrys may be sufficient cause for a major "decontamination" by qualified
technicians wearing special protective clothing. Stachybotrys species produce black colonies on dry wall, 10 of 11 9/30/99 11:50 AM Source http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds/Source.html ceiling tiles and other materials containing
cellulose. The easiest way to confirm the presence
of Stachybotrys is to press a piece of cellulose
tape against the mouldy spot and then examine it
sticky side up on a slide under a microscope for
the characteristic spore-bearing structures. The
image at right illustrates conidiophores and
conidia of a Stachybotrys species collected on
tape from a basement in southern Quebec. Not all
moulds are identifiable using this technique, but it
works well for many, including Stachybotrys. 11 of 11 9/30/99 11:50 AM |
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