filamentous fungi belonging to Zygomycetes and
Ascomycetes (Buchalo et al. 2000). Algae of the genus
Dunaliella were often encountered in the Dead Sea but
also in artificial ecosystems such as salt marshes.
10.4.7 Biotechnological Applications
Moderate halophilic microorganisms can be the source of
very promising potential technological applications, because
some of them produce molecules that are of industrial interest (polymers or compatible solutes, bioemulsifiers, etc.).
Many studies on hydrolases produced by halophiles have
been reported because of their stability in solutions
containing organic solvents (Moreno et al. 2013).
Most of these organisms require few nutrients to grow.
They may also use a fairly wide range of organic compounds
as carbon and energy sources. These organisms growing at
high salt concentrations significantly reduce the risk of contamination in industrial processes.
The biotechnological applications where moderate/
extreme halophiles are involved include the fermentation of
soy sauce by halotolerant/moderately halophilic bacteria and
archaea which is used in the preparation in a Vietnamese fish
dipping sauce called “nuoc mam.” Moderate halophilic bacteria accumulate large amounts of molecules of low molecular
weight in order to face the osmotic pressure. The compatible
solutes glycine, betaine, and ectoine can be used as protective
agents against salinity stress, heat denaturation, freezing, or
drying (Shivanand and Mugeraya 2011). They also have a
high interest in the pharmaceutical and cosmetics industries.
Recent advances in fermentation processes and genetics of
halophilic prokaryotes have rendered possible the overproduction of these compatible solutes (Vargas et al. 2004).
It is also possible to perform gene transfer from moderately halophiles to give to plants, such as wheat, rice, and
barley, the capacity to adapt salted environmental conditions
and drought. Indigenous halophilic microorganisms to oilfield waters could be extremely valuable for enhancing
petroleum recovery by producing polysaccharides having
bio-emulsifying properties. These compounds have the
properties to resist to heat denaturation. They have higher
viscosity values at high temperatures as compared to
polymers currently commercialized such as xanthan gum.
For example, Halomonas eurihalina can produce large
amounts of a polyanionic extracellular polysaccharide (EPS
V2-7) with emulsifying properties that can be used in food
and pharmaceutical industries.
In recent years, there is an increase in the amount of
saline waters rejected by chemical and pharmaceutical
industries. Conventional microbiological treatments are not
applicable to these salted wastes, but the use of halotolerant/
halophilic microorganisms should be taken into consideration
for treating them either aerobically or anaerobically. As an
example, the treatment of high saline wastewater was successfully for the removal of phenolic or aromatic compounds
and highly toxic molecules such as organophosphates (Oren
et al. 1992).
Many other potential applications for halophilic
microorganisms can be considered for biotechnology (Kivisto
and Karp 2011), among which are: the recovery of phosphate
and the search for new bioactive molecules such as antibiotics,
surfactants, or new enzymes (restriction endonucleases).
Regarding the food industry, carotenes can be extracted
from halophilic microorganisms to be used as food additives
or as food-coloring agents.
A fascinating application has been considered for a protein
originating from the cytoplasmic membrane of
Halobacterium halophilum (bacteriorhodopsin). This protein
acts as a proton pump to establish a gradient between both
sides of the membrane (cf. Sect. 3.3.4). An electronic microchip composed of a thin layer of bacteriorhodopsin would be
able to store more informations than a silicon chip, thus
processing the information faster. These microchips will be
probably helpful in high performance-computer production
and even mass-producing vision systems for robotics.
Considered for long as environments hostile to all forms of
life, it is only recently that hypersaline ecosystems have been
intensively studied. Microorganisms that inhabit such
ecosystems have a great diversity in terms of phylogenetic
characteristics, shapes, metabolisms, and also strategies to
develop in these hypersaline environments. They have
promising biotechnological potentialities that can be used in
different industrial sectors (e.g., pharmacy, oil production).
Further investigations are however still needed to improve our
knowledge on the existing microbial diversity and associated
metabolisms in these extreme environments.
10.5 Piezophilic Microorganisms
10.5.1 Presentation
Hydrostatic pressure is a physical parameter, typical for
aquatic environments. Hydrostatic pressure is the ratio of a
force applied onto an area. A force of 1 N onto a surface of
1 m
2 corresponds to a pressure of 1 Pascal (Pa). Other units are
sometimes used as shown below but the legal unit is Pascal:
1 Pa ¼ 1:10
À5 bar ¼ 9:8692:10
À4 atm ¼ 1:4503:10
À4 PSI
¼ 7:5003:10
À3 Torr
To calculate the hydrostatic pressure applied by a liquid
onto a given area, gravity acceleration, volumic mass of the
liquid, and depth must be taken into account. More simply, for
10 The Extreme Conditions of Life on the Planet and Exobiology
375
Ascomycetes (Buchalo et al. 2000). Algae of the genus
Dunaliella were often encountered in the Dead Sea but
also in artificial ecosystems such as salt marshes.
10.4.7 Biotechnological Applications
Moderate halophilic microorganisms can be the source of
very promising potential technological applications, because
some of them produce molecules that are of industrial interest (polymers or compatible solutes, bioemulsifiers, etc.).
Many studies on hydrolases produced by halophiles have
been reported because of their stability in solutions
containing organic solvents (Moreno et al. 2013).
Most of these organisms require few nutrients to grow.
They may also use a fairly wide range of organic compounds
as carbon and energy sources. These organisms growing at
high salt concentrations significantly reduce the risk of contamination in industrial processes.
The biotechnological applications where moderate/
extreme halophiles are involved include the fermentation of
soy sauce by halotolerant/moderately halophilic bacteria and
archaea which is used in the preparation in a Vietnamese fish
dipping sauce called “nuoc mam.” Moderate halophilic bacteria accumulate large amounts of molecules of low molecular
weight in order to face the osmotic pressure. The compatible
solutes glycine, betaine, and ectoine can be used as protective
agents against salinity stress, heat denaturation, freezing, or
drying (Shivanand and Mugeraya 2011). They also have a
high interest in the pharmaceutical and cosmetics industries.
Recent advances in fermentation processes and genetics of
halophilic prokaryotes have rendered possible the overproduction of these compatible solutes (Vargas et al. 2004).
It is also possible to perform gene transfer from moderately halophiles to give to plants, such as wheat, rice, and
barley, the capacity to adapt salted environmental conditions
and drought. Indigenous halophilic microorganisms to oilfield waters could be extremely valuable for enhancing
petroleum recovery by producing polysaccharides having
bio-emulsifying properties. These compounds have the
properties to resist to heat denaturation. They have higher
viscosity values at high temperatures as compared to
polymers currently commercialized such as xanthan gum.
For example, Halomonas eurihalina can produce large
amounts of a polyanionic extracellular polysaccharide (EPS
V2-7) with emulsifying properties that can be used in food
and pharmaceutical industries.
In recent years, there is an increase in the amount of
saline waters rejected by chemical and pharmaceutical
industries. Conventional microbiological treatments are not
applicable to these salted wastes, but the use of halotolerant/
halophilic microorganisms should be taken into consideration
for treating them either aerobically or anaerobically. As an
example, the treatment of high saline wastewater was successfully for the removal of phenolic or aromatic compounds
and highly toxic molecules such as organophosphates (Oren
et al. 1992).
Many other potential applications for halophilic
microorganisms can be considered for biotechnology (Kivisto
and Karp 2011), among which are: the recovery of phosphate
and the search for new bioactive molecules such as antibiotics,
surfactants, or new enzymes (restriction endonucleases).
Regarding the food industry, carotenes can be extracted
from halophilic microorganisms to be used as food additives
or as food-coloring agents.
A fascinating application has been considered for a protein
originating from the cytoplasmic membrane of
Halobacterium halophilum (bacteriorhodopsin). This protein
acts as a proton pump to establish a gradient between both
sides of the membrane (cf. Sect. 3.3.4). An electronic microchip composed of a thin layer of bacteriorhodopsin would be
able to store more informations than a silicon chip, thus
processing the information faster. These microchips will be
probably helpful in high performance-computer production
and even mass-producing vision systems for robotics.
Considered for long as environments hostile to all forms of
life, it is only recently that hypersaline ecosystems have been
intensively studied. Microorganisms that inhabit such
ecosystems have a great diversity in terms of phylogenetic
characteristics, shapes, metabolisms, and also strategies to
develop in these hypersaline environments. They have
promising biotechnological potentialities that can be used in
different industrial sectors (e.g., pharmacy, oil production).
Further investigations are however still needed to improve our
knowledge on the existing microbial diversity and associated
metabolisms in these extreme environments.
10.5 Piezophilic Microorganisms
10.5.1 Presentation
Hydrostatic pressure is a physical parameter, typical for
aquatic environments. Hydrostatic pressure is the ratio of a
force applied onto an area. A force of 1 N onto a surface of
1 m
2 corresponds to a pressure of 1 Pascal (Pa). Other units are
sometimes used as shown below but the legal unit is Pascal:
1 Pa ¼ 1:10
À5 bar ¼ 9:8692:10
À4 atm ¼ 1:4503:10
À4 PSI
¼ 7:5003:10
À3 Torr
To calculate the hydrostatic pressure applied by a liquid
onto a given area, gravity acceleration, volumic mass of the
liquid, and depth must be taken into account. More simply, for
10 The Extreme Conditions of Life on the Planet and Exobiology
375