2.3
Third Symbiont “Yeast”
In the study of Spribille et al. [9] is stated that many common lichens consist of a
known ascomycete, the autotrophic photosynthesizing partner, and unexpectedly
specific basidiomycete yeast (Fig. 1d). These yeasts are anchored in the cortex of
lichen thallus and their abundance correlates with previously unexplained variations
of the phenotype.
3
Anatomy and Morphology
Lichen morphology and anatomy is highly adapted to environmental restrictions; the
mycobiont forms the exhabitant and the photobiont is the inhabitant [22]. The lichen
“body” is called thallus. In the cross section (Fig. 2c), the lichen thallus usually
consists of the upper cortex, a photosynthetic layer, the medulla, and the lower
cortex. Some species also developed a central cord which has a support function
(Fig. 2a, b). The thickness of the layers can vary in different species which is a
response to the different environmental conditions.
Symbiosis is a source of dynamic evolution which is reflected by the different
growth forms of thalli [23]. Many different thalli structures are known [24, 25], but
they can be divided into three morphological types: (Fig. 3a) fruticose, (Fig. 3b)
crustose, and (Fig. 3c) foliose. Other types can be included into these main three
types. For example, Cladonia macilenta is lichen with squamulose bases and fruticose
fruiting structures which are called podetia (Fig. 3d). Lepraria species have leprose,
crustose lichen thalli with a powdery or granular surface. Genus Collema, Leptogium,
or Lathagrium are characteristic of their gelatinous foliose thallus (Fig. 3e).
Crustose (Fig. 3a) lichens are tightly attached to the substrate by whole thalli, and
it is very hard to remove them without any damage. These lichens usually grow on
rocks or barks and colonize extreme habitats, including metal rich substrates.
Unfortunately, the physiological studies of these lichens are very poor due to the
complicated removal from substrate and low biomass production for routine analysis
[26]. Extreme examples are endolithic species which penetrate a rock surface and
only fruiting bodies are exposed (Fig. 3f).
Foliose lichens (Fig. 3b) are known as leafy-like. They are partially attached to
the substrate or in one single point. The thallus is usually divided into lobes
(Parmelia sp.) with various degrees of branching, but in some species (Umbilicaria
sp.) the thallus is from one single unbranched lobe or a “multilobe” with limited
branching [8]. According to their biomass and easy collection, they are used in
biochemical and ecophysiological studies [26].
Fruticose lichens (Fig. 3c, d) are known as hair-like or strap-shaped. The lobes are
usually flat or cylindrical. The thallus can grow horizontally or vertically (Cladonia
sp.) or even hanging (Usnea sp.). The branching of lobes may be different within the
systematic groups or even a single genus. Fruticose lichens are growing usually on
tree barks but also on the ground. As with the foliose types, lichenologists prefer for
experiments fruticose growth forms of thalli due to the easy removal from surface.
9 Lichen Metabolites: An Overview of Some Secondary Metabolites and Their. . .
179
Third Symbiont “Yeast”
In the study of Spribille et al. [9] is stated that many common lichens consist of a
known ascomycete, the autotrophic photosynthesizing partner, and unexpectedly
specific basidiomycete yeast (Fig. 1d). These yeasts are anchored in the cortex of
lichen thallus and their abundance correlates with previously unexplained variations
of the phenotype.
3
Anatomy and Morphology
Lichen morphology and anatomy is highly adapted to environmental restrictions; the
mycobiont forms the exhabitant and the photobiont is the inhabitant [22]. The lichen
“body” is called thallus. In the cross section (Fig. 2c), the lichen thallus usually
consists of the upper cortex, a photosynthetic layer, the medulla, and the lower
cortex. Some species also developed a central cord which has a support function
(Fig. 2a, b). The thickness of the layers can vary in different species which is a
response to the different environmental conditions.
Symbiosis is a source of dynamic evolution which is reflected by the different
growth forms of thalli [23]. Many different thalli structures are known [24, 25], but
they can be divided into three morphological types: (Fig. 3a) fruticose, (Fig. 3b)
crustose, and (Fig. 3c) foliose. Other types can be included into these main three
types. For example, Cladonia macilenta is lichen with squamulose bases and fruticose
fruiting structures which are called podetia (Fig. 3d). Lepraria species have leprose,
crustose lichen thalli with a powdery or granular surface. Genus Collema, Leptogium,
or Lathagrium are characteristic of their gelatinous foliose thallus (Fig. 3e).
Crustose (Fig. 3a) lichens are tightly attached to the substrate by whole thalli, and
it is very hard to remove them without any damage. These lichens usually grow on
rocks or barks and colonize extreme habitats, including metal rich substrates.
Unfortunately, the physiological studies of these lichens are very poor due to the
complicated removal from substrate and low biomass production for routine analysis
[26]. Extreme examples are endolithic species which penetrate a rock surface and
only fruiting bodies are exposed (Fig. 3f).
Foliose lichens (Fig. 3b) are known as leafy-like. They are partially attached to
the substrate or in one single point. The thallus is usually divided into lobes
(Parmelia sp.) with various degrees of branching, but in some species (Umbilicaria
sp.) the thallus is from one single unbranched lobe or a “multilobe” with limited
branching [8]. According to their biomass and easy collection, they are used in
biochemical and ecophysiological studies [26].
Fruticose lichens (Fig. 3c, d) are known as hair-like or strap-shaped. The lobes are
usually flat or cylindrical. The thallus can grow horizontally or vertically (Cladonia
sp.) or even hanging (Usnea sp.). The branching of lobes may be different within the
systematic groups or even a single genus. Fruticose lichens are growing usually on
tree barks but also on the ground. As with the foliose types, lichenologists prefer for
experiments fruticose growth forms of thalli due to the easy removal from surface.
9 Lichen Metabolites: An Overview of Some Secondary Metabolites and Their. . .
179