B. Fungal Role in the Marine Environment
Fungi are widely distributed in marine environments from the deep sea to polar ice covers.
They occur in sediments and are found in all
kinds of living and dead organic matter (Hyde
et al. 2000; Jones 2011). Their numbers in the
water column of the oceans are low compared
to bacteria, and most of the studies on marine
fungi have been made with those associated
with marine sediments, specific substrates like
driftwood or with living macroorganisms such
as algae, corals, and sponges (Imhoff 2016).
Cultivation-based data and molecular functional studies demonstrated that fungi in the
ocean cover a variety of ecological roles. As
known for the terrestrial habitats, many marine
fungi act as saprophytes, especially degrading
macromolecular material as the starter for the
microbial food chain (Scheu 2002). Fungi,
besides directly serving as nutrient source,
also help in removing hardly digestible compounds present in plant parts (Raghukumar
et al. 2004b). The fibrous lignocellulose tissues
may be softened by the lignocellulosedegrading enzymes of the saprophytic fungi.
Fungi might also supply essential nutrients to
detritivores. Thereby, fungi play a crucial role
in the chemical cycling of carbon and nitrogen
in the sea sediments (Karthikeyan et al. 2014).
Especially deep-sea fungi were postulated to
significantly contribute to aggregate formation
and carbon contribution (Raghukumar et al.
2004b).
Despite the rise of metagenome studies
especially focusing on the marine environment,
metagenome data specifically targeting fungi
are missing. The use of NGS techniques opened
a new era for marine fungal biodiversity
research, tapping an unexpected fungal diversity and richness in the marine realm (e.g.,
Amend et al. 2012; Redou et al. 2014; Richards
et al. 2012; Hassett and Gradinger 2016; Ra ¨ma ¨
et al. 2014). Generally, the fungal abundance in
marine systems can vary greatly. The available
studies suggest fungi to be represented in sediments and associated to macroorganisms with
up to 30% of the obtained sequences but also
show high abundances in the open water column. The fungal sequences found do illustrate
the gap between molecular and cultural
approaches; especially the deep lineages of
fungi are not well represented in the cultural
collections, and the overlap of the described
diversity is still limited. However, the molecular
studies underline the untapped potential of
fungal diversity in the oceans.
Marine fungi can be repeatedly isolated
from living organisms. Both plants and animals
harbor a number of fungi, often with representatives of Acremonium, Aspergillus, Fusarium,
Penicillium, Phoma, and Trichoderma (Wang
2006). Due to their accumulation within the
animal or plant, usually a large number of fungal species can be isolated, which increases the
probability to find representatives of less common taxa. For example, fungi belonging to the
less common genera Beauveria, Botryosphaeria, Epicoccum, Tritirachium, and Paraphaeosphaeria have been obtained from
marine sponges (Zhang et al. 2009). The fungi
do occur on surfaces but also in specialized
parts of macroorganisms. For instance, it was
shown that the sponge Tethia aurantia harbors
different fungal communities in its different
tissue layers (Wiese et al. 2011; Thiel et al.
2007).
It is assumed that associations to macroorganisms are based on different ecological roles
including mutual or even symbiotic beneficial
interaction, saprophytic activity on injured
parts of the host and pathogenicity (Richards
et al. 2012; Yarden 2014). Aspergillosis in
marine animals is a well-studied example of
fungal pathogenicity. Aspergillus sydowii is a
pathogen, e.g., of the Caribbean sea fan (Gorgonia spp.) as well as other gorgonian corals. The
impact of disease ranges from local mass
impact to partial tissue loss and eventual recovery. A. sydowii is known as a common terrestrial soil fungus but was shown to prosper in
both terrestrial and marine environments.
Although A. sydowii is common and cosmopolitan, it had not previously been recognized
causing disease in terrestrial plants or animals.
It was concluded that isolates taken from diseased corals have acquired specific pathogenic
potential not seen in isolates from other
16 Biotechnology of Marine Fungi: New Workhorses and Applications
401
Fungi are widely distributed in marine environments from the deep sea to polar ice covers.
They occur in sediments and are found in all
kinds of living and dead organic matter (Hyde
et al. 2000; Jones 2011). Their numbers in the
water column of the oceans are low compared
to bacteria, and most of the studies on marine
fungi have been made with those associated
with marine sediments, specific substrates like
driftwood or with living macroorganisms such
as algae, corals, and sponges (Imhoff 2016).
Cultivation-based data and molecular functional studies demonstrated that fungi in the
ocean cover a variety of ecological roles. As
known for the terrestrial habitats, many marine
fungi act as saprophytes, especially degrading
macromolecular material as the starter for the
microbial food chain (Scheu 2002). Fungi,
besides directly serving as nutrient source,
also help in removing hardly digestible compounds present in plant parts (Raghukumar
et al. 2004b). The fibrous lignocellulose tissues
may be softened by the lignocellulosedegrading enzymes of the saprophytic fungi.
Fungi might also supply essential nutrients to
detritivores. Thereby, fungi play a crucial role
in the chemical cycling of carbon and nitrogen
in the sea sediments (Karthikeyan et al. 2014).
Especially deep-sea fungi were postulated to
significantly contribute to aggregate formation
and carbon contribution (Raghukumar et al.
2004b).
Despite the rise of metagenome studies
especially focusing on the marine environment,
metagenome data specifically targeting fungi
are missing. The use of NGS techniques opened
a new era for marine fungal biodiversity
research, tapping an unexpected fungal diversity and richness in the marine realm (e.g.,
Amend et al. 2012; Redou et al. 2014; Richards
et al. 2012; Hassett and Gradinger 2016; Ra ¨ma ¨
et al. 2014). Generally, the fungal abundance in
marine systems can vary greatly. The available
studies suggest fungi to be represented in sediments and associated to macroorganisms with
up to 30% of the obtained sequences but also
show high abundances in the open water column. The fungal sequences found do illustrate
the gap between molecular and cultural
approaches; especially the deep lineages of
fungi are not well represented in the cultural
collections, and the overlap of the described
diversity is still limited. However, the molecular
studies underline the untapped potential of
fungal diversity in the oceans.
Marine fungi can be repeatedly isolated
from living organisms. Both plants and animals
harbor a number of fungi, often with representatives of Acremonium, Aspergillus, Fusarium,
Penicillium, Phoma, and Trichoderma (Wang
2006). Due to their accumulation within the
animal or plant, usually a large number of fungal species can be isolated, which increases the
probability to find representatives of less common taxa. For example, fungi belonging to the
less common genera Beauveria, Botryosphaeria, Epicoccum, Tritirachium, and Paraphaeosphaeria have been obtained from
marine sponges (Zhang et al. 2009). The fungi
do occur on surfaces but also in specialized
parts of macroorganisms. For instance, it was
shown that the sponge Tethia aurantia harbors
different fungal communities in its different
tissue layers (Wiese et al. 2011; Thiel et al.
2007).
It is assumed that associations to macroorganisms are based on different ecological roles
including mutual or even symbiotic beneficial
interaction, saprophytic activity on injured
parts of the host and pathogenicity (Richards
et al. 2012; Yarden 2014). Aspergillosis in
marine animals is a well-studied example of
fungal pathogenicity. Aspergillus sydowii is a
pathogen, e.g., of the Caribbean sea fan (Gorgonia spp.) as well as other gorgonian corals. The
impact of disease ranges from local mass
impact to partial tissue loss and eventual recovery. A. sydowii is known as a common terrestrial soil fungus but was shown to prosper in
both terrestrial and marine environments.
Although A. sydowii is common and cosmopolitan, it had not previously been recognized
causing disease in terrestrial plants or animals.
It was concluded that isolates taken from diseased corals have acquired specific pathogenic
potential not seen in isolates from other
16 Biotechnology of Marine Fungi: New Workhorses and Applications
401