15.6.3 Mycoparasitic Fungi
These attack other fungi. They were first described as early as around the year 1800
by mycologists who were interested in the diseases of plants. Mycoparasitic plants
can act as natural enemies of the phytopathogenic fungi that are causative agents of
plant diseases. For this reason research of some prospective fungi for the protection
of agricultural crops and fruit trees has been going on since the early twentieth
century and is still active now.
Some mycoparasitic fungi are biotrophic meaning that they grow on live mycelium of other fungi, and most of those biotrophs belong to the class Zygomycetes.
Other mycoparasites are known for necrotrophy, meaning they attack and destroy
their hosts. Some mycoparasitic fungi include mitosporic genera Gliocladium,
Pythium, and Trichoderma as well as genera from the former class Zygomycetes,
specifically the genera Dicranophora, Spinellus, and Syzygites.
Special attention is reserved for the species Pythium oligandrum, which differs
diametrically from the other species of the genera Pythium by its mycoparasitism. It
attacks fungi and enzymatically decomposes the mycelia and also some reproductive
organs of the attacked fungi, and then uses the products of those enzymatic degradative
processes for its own nutrition. From another point of view, the pathogenicity of P.
oligandum is brought about partly by its direct antagonistic action (¼ its
mycoparasitism) and partly by its formation of antimicrobial compounds. This fact
was confirmed by Nicole Benhamou et al. (1999) when Phytophthora megasperma was
inactivated at distance by P. oligandrum without any direct contact with this pathogen.
Later, in 2001 Benhamou with her coworker Chantal Garand (Benhamou and Garand
2001) proved that a protein called oligandrin, produced by P. oligandrum, causes a
systemic resistance of tomatoes against infection by a fungus of the genus Fusarium.
However, P. oligandrum must possess a certain ability to distinguish between its
own cells and the cells of a phytopathogenic fungus. Otherwise, it could destroy its
own organism by its cellulolytic enzymes. This question of how this recognition
occurs has not been solved yet. Thus, P. oligandrum acts as a biological fungicide
(biofungicide). Commercial preparations created on the basis of this fungus are
already used not only in agriculture for plant protection, but also in medicine for
the treatment of various mycotic ailments.
15.7 Predation
Let us imagine a relationship between a predator and its prey. One organism, the
predator, violently destroys and then consumes another organism, the prey. This is a
common natural event not only in the animal kingdom, but also in amongst microscopic organisms. On the microscopic level, the predators of bacteria are, for
example, myxobacteria, protozoa, and some fungi. For instance, a flagellate of the
genus Ochromonas of the family Chromulinaceae consumes not only whole bacteria, but also yeast and algae. Bacteria also constitute a frequent source of nutrition for
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These attack other fungi. They were first described as early as around the year 1800
by mycologists who were interested in the diseases of plants. Mycoparasitic plants
can act as natural enemies of the phytopathogenic fungi that are causative agents of
plant diseases. For this reason research of some prospective fungi for the protection
of agricultural crops and fruit trees has been going on since the early twentieth
century and is still active now.
Some mycoparasitic fungi are biotrophic meaning that they grow on live mycelium of other fungi, and most of those biotrophs belong to the class Zygomycetes.
Other mycoparasites are known for necrotrophy, meaning they attack and destroy
their hosts. Some mycoparasitic fungi include mitosporic genera Gliocladium,
Pythium, and Trichoderma as well as genera from the former class Zygomycetes,
specifically the genera Dicranophora, Spinellus, and Syzygites.
Special attention is reserved for the species Pythium oligandrum, which differs
diametrically from the other species of the genera Pythium by its mycoparasitism. It
attacks fungi and enzymatically decomposes the mycelia and also some reproductive
organs of the attacked fungi, and then uses the products of those enzymatic degradative
processes for its own nutrition. From another point of view, the pathogenicity of P.
oligandum is brought about partly by its direct antagonistic action (¼ its
mycoparasitism) and partly by its formation of antimicrobial compounds. This fact
was confirmed by Nicole Benhamou et al. (1999) when Phytophthora megasperma was
inactivated at distance by P. oligandrum without any direct contact with this pathogen.
Later, in 2001 Benhamou with her coworker Chantal Garand (Benhamou and Garand
2001) proved that a protein called oligandrin, produced by P. oligandrum, causes a
systemic resistance of tomatoes against infection by a fungus of the genus Fusarium.
However, P. oligandrum must possess a certain ability to distinguish between its
own cells and the cells of a phytopathogenic fungus. Otherwise, it could destroy its
own organism by its cellulolytic enzymes. This question of how this recognition
occurs has not been solved yet. Thus, P. oligandrum acts as a biological fungicide
(biofungicide). Commercial preparations created on the basis of this fungus are
already used not only in agriculture for plant protection, but also in medicine for
the treatment of various mycotic ailments.
15.7 Predation
Let us imagine a relationship between a predator and its prey. One organism, the
predator, violently destroys and then consumes another organism, the prey. This is a
common natural event not only in the animal kingdom, but also in amongst microscopic organisms. On the microscopic level, the predators of bacteria are, for
example, myxobacteria, protozoa, and some fungi. For instance, a flagellate of the
genus Ochromonas of the family Chromulinaceae consumes not only whole bacteria, but also yeast and algae. Bacteria also constitute a frequent source of nutrition for
15 Microscopic World and the Phenomenon of Symbiosis in the Natural Environment
253