Part E | 26.3
654 Part E Marine Microbiology and Biotechnology
laboratory in large quantities [26.17, 32]. Therefore, microbial blue biotechnology has the advantage of being
a more sustainable activity, by avoiding the collection
of marine organisms from their habitat.
26.3 Biotechnology of Marine Microbes, from Viruses
to Microbial Eukaryotes
26.3.1 Marine Viruses
Viruses are ubiquitous biotic components of pelagic and
benthic ecosystems. They influence lateral gene transfer, genetic diversity, and bacterial mortality [26.33,
34]. Marine viruses were not studied until 1989, but
are now recognized as the most abundant biological entities in the sea (typically 10
7 viruses ml
1 ;
[26.35]. Phage diversity studies were initially restricted
by the requirement for cultivated hosts, but recent
applications of culture-independent techniques have revealed an enormous, and unexpected, viral diversity
in marine ecosystems [26.35, 36]. Archaeal, bacterial,
and eukaryotic viruses are cosmopolitan and abundant
throughout the world’s oceans [26.37]. Their host range
covers all known marine organisms, from prokaryotes
to fishes and mammals. Phages are particularly abundant in marine sediments, and viral infection represents
a substantial source of mortality in deep-sea benthic
ecosystems [26.38]. Many lines of evidence have suggested that phage diversity is virtually immense, but
studies describing marine phage diversity are nowadays
limited [26.39].
The genetic pool of marine viruses has enormous
potential for biotechnology, but the use of marine
viruses as biotechnological agents is still at an early
stage. One potential application can be in medicine, to
provide new solutions to sanitary problems for humans
or other organisms. Potential applications of viruses in
biomedicine, some of them already explored, include
the use of viral vectors (gene transfer, gene therapy and
vaccine development) and the use of viruses for protein expression and oncolytic viruses (e.g., virotherapy
for treating tumors). There are currently no studies involving marine viruses but, given the magnitude of the
diversity of marine phages, potential biotechnological
exploitations can be expected.
Phages were used in early forms of biotechnology to control bacterial infections [26.33, 40]. Phage
therapy was abandoned due to contrasting results and
the discovery of antibiotics. It is, however, currently
the subject of revived interest because of the emergence of antibiotic-resistance as either a biomedical and
environmental problem. Some authors have explored
the biotechnological usefulness of marine viruses as
agents for curing coral diseases. The rapid emergence
of infectious diseases in tropical stony corals is causing serious damage to coral reef ecosystems [26.41].
Efrony et al. [26.42] recently isolated two phages of
known coral bacterial pathogens (Vibrio coralliilyticus
and Thalassomonas loyana) and used them in controlled aquarium experiments to explore their utility
in coral phage therapy. The results showed that diseases could be successfully controlled by the use of
pathogen-specific phages, suggesting the possible usefulness of phage therapy. Cohen et al. [26.43] and other
authors recently confirmed the potential application
of marine viruses in the treatment of coral diseases.
Other potential biotechnological applications of marine
viruses are in the control of harmful algal blooms. Onji
et al. [26.44] reported on the isolation of two viruslike agents that are able to suppress the growth of
Gymnodinium mikimoto, a red-tide-forming marine dinoflagellate.
The exploration of the diversity of the marine virome has just begun. The discovery of novel genes
and proteins with unknown functions, with potential
biotechnological applications, can be expected, and deserves further in-depth investigations.
26.3.2 Marine Archaea
Archaea are evolutionarily unique prokaryotes, as genetically distant from bacteria as they are from eucarya [26.14]. They were historically assumed to live
only in extremophilic habitats, but two decades of studies have revealed that they are abundant, widespread,
and ecologically important members of the marine
biota [26.45, 46]. The discovery of archaea was a significant breakthrough in the history of biology, leading to
the replacement of the prokaryote/eukaryote dichotomy
by a trinity of domains, the archaea, bacteria and eukarya [26.47].
Marine archaea are an interesting source for
biotechnology, however only few fields of biotechnological exploitations have so far been successfully
654 Part E Marine Microbiology and Biotechnology
laboratory in large quantities [26.17, 32]. Therefore, microbial blue biotechnology has the advantage of being
a more sustainable activity, by avoiding the collection
of marine organisms from their habitat.
26.3 Biotechnology of Marine Microbes, from Viruses
to Microbial Eukaryotes
26.3.1 Marine Viruses
Viruses are ubiquitous biotic components of pelagic and
benthic ecosystems. They influence lateral gene transfer, genetic diversity, and bacterial mortality [26.33,
34]. Marine viruses were not studied until 1989, but
are now recognized as the most abundant biological entities in the sea (typically 10
7 viruses ml
1 ;
[26.35]. Phage diversity studies were initially restricted
by the requirement for cultivated hosts, but recent
applications of culture-independent techniques have revealed an enormous, and unexpected, viral diversity
in marine ecosystems [26.35, 36]. Archaeal, bacterial,
and eukaryotic viruses are cosmopolitan and abundant
throughout the world’s oceans [26.37]. Their host range
covers all known marine organisms, from prokaryotes
to fishes and mammals. Phages are particularly abundant in marine sediments, and viral infection represents
a substantial source of mortality in deep-sea benthic
ecosystems [26.38]. Many lines of evidence have suggested that phage diversity is virtually immense, but
studies describing marine phage diversity are nowadays
limited [26.39].
The genetic pool of marine viruses has enormous
potential for biotechnology, but the use of marine
viruses as biotechnological agents is still at an early
stage. One potential application can be in medicine, to
provide new solutions to sanitary problems for humans
or other organisms. Potential applications of viruses in
biomedicine, some of them already explored, include
the use of viral vectors (gene transfer, gene therapy and
vaccine development) and the use of viruses for protein expression and oncolytic viruses (e.g., virotherapy
for treating tumors). There are currently no studies involving marine viruses but, given the magnitude of the
diversity of marine phages, potential biotechnological
exploitations can be expected.
Phages were used in early forms of biotechnology to control bacterial infections [26.33, 40]. Phage
therapy was abandoned due to contrasting results and
the discovery of antibiotics. It is, however, currently
the subject of revived interest because of the emergence of antibiotic-resistance as either a biomedical and
environmental problem. Some authors have explored
the biotechnological usefulness of marine viruses as
agents for curing coral diseases. The rapid emergence
of infectious diseases in tropical stony corals is causing serious damage to coral reef ecosystems [26.41].
Efrony et al. [26.42] recently isolated two phages of
known coral bacterial pathogens (Vibrio coralliilyticus
and Thalassomonas loyana) and used them in controlled aquarium experiments to explore their utility
in coral phage therapy. The results showed that diseases could be successfully controlled by the use of
pathogen-specific phages, suggesting the possible usefulness of phage therapy. Cohen et al. [26.43] and other
authors recently confirmed the potential application
of marine viruses in the treatment of coral diseases.
Other potential biotechnological applications of marine
viruses are in the control of harmful algal blooms. Onji
et al. [26.44] reported on the isolation of two viruslike agents that are able to suppress the growth of
Gymnodinium mikimoto, a red-tide-forming marine dinoflagellate.
The exploration of the diversity of the marine virome has just begun. The discovery of novel genes
and proteins with unknown functions, with potential
biotechnological applications, can be expected, and deserves further in-depth investigations.
26.3.2 Marine Archaea
Archaea are evolutionarily unique prokaryotes, as genetically distant from bacteria as they are from eucarya [26.14]. They were historically assumed to live
only in extremophilic habitats, but two decades of studies have revealed that they are abundant, widespread,
and ecologically important members of the marine
biota [26.45, 46]. The discovery of archaea was a significant breakthrough in the history of biology, leading to
the replacement of the prokaryote/eukaryote dichotomy
by a trinity of domains, the archaea, bacteria and eukarya [26.47].
Marine archaea are an interesting source for
biotechnology, however only few fields of biotechnological exploitations have so far been successfully