already harnessed to this type of business and the results are
promising.
10.2.3.1 Arctic and Antarctic Oceans
In these environments, below 60
south latitude, the temperature of the water varies between À1.9 and 5
C. The selection
pressure is high due to the relative stability of these
temperatures as compared to the same latitude terrestrial
environments. In the Arctic Ocean, below the permanent ice,
densities of 10
2 mL
À1 of heterotrophic bacteria have been
reported. Populations do not appear very different when comparing the Arctic to the Antarctic; so at the two poles, Alphaand Gammaproteobacteria and Bacteroidetes dominate with
97 % of the phylotypes identified being common to Arctic and
Antarctic. In Antarctica a large fluctuation of marine biomass
depending on the season, which reflects changes in temperature and light, is observed. Large populations of Flavobacteria
whose abundance is connected with chlorophyll and nutrients
are found on surface. Archaea are also abundant and represent
about 30 % of the biomass of prokaryotes. The most common
types of bacteria found in Arctic and Antarctic seawaters are
Alteromonas Colwellia, Glaciecola, Pseudoalteromonas,
Shewanella, and Polaribacter.
10.2.3.2 Deep Waters
Sixty percent of the Earth’s surface is covered by seas deeper
than 1,000 m. The hydrostatic pressure of these
environments is more than 110 MPa and temperatures
often below 4
C (except in hydrothermal vents where temperature can reach 370
C). Microorganisms capable of
withstanding these pressures and temperatures are called
psychropiezophiles. The first bacterium of this type was
discovered in 1979. It is a Spirillum-like bacterium (strain
CNPT-3) that grows well at 50 MPa and is unable to grow at
atmospheric pressure. Numerous psychropiezophilic bacteria have been isolated and characterized. It turns out that
they all belong to the group of Gammaproteobacteria
according to the classification based on the sequences of
16S and 5S rRNA genes. These bacteria are divided into
five predominant genera: Photobacterium, Colwellia,
Moritella, Shewanella, and Psychromonas. Regardless of
the type to which these bacteria belong, their membranes
have a high rate of unsaturated fatty acids to maintain fluidity at low temperature and high pressure as well. Depending
on genus to which bacteria belong, they also produce
long-chain polyunsaturated fatty acids including
eicosapentaenoic acid and/or docosahexaenoic acid (cf.
Sect. 17.7.8). The proportion of these polyunsaturated fatty
acids in the membrane varies between 50 and 70 %. However, production of these fatty acids does not seem to be
required for growth of psychropiezophiles. As an example,
Psychromonas profunda strain SS9 only produces monounsaturated fatty acids.
10.2.3.3 Sea Ice
Sea ice represents a particular habitat (Fig. 10.1) because of
temperature possibly dropping to À35
C and its semisolid
state. Its formation causes the expulsion of the dissolved salts
of the solid matrix but also the formation of a labyrinth with
liquid veins varying with temperature. Salinity can reach a
value of 14.5 % at À10
C compared to a value of 3.4 %
observed at À1.9
C. A very large concentration of dissolved
organic matter (DOM) is recorded, which transforms these
veins in habitats where many microorganisms develop. The
composition of these veins is not constant, resulting in a
desalination process increasing with the age of ice. Temperature gradients also exist within it, from the surface to the icewater interface, which makes this habitat a particularly heterogeneous environment. The total areas of these liquid streams
are of the magnitude order of 0.6–4.0 m
2 kg
À1 of ice. Heterotrophic bacteria are the main groups of prokaryotes detected.
They are psychrotrophic but also halotolerant; cyanobacteria
are also present. Unlike free waters, archaea are poorly
represented with about 0–3 % of total cells. The presence of
exopolysaccharides produced by microorganisms may act as
cryoprotectants but also as nutrient traps (see below) thus
favoring the colonization of habitats. More than 100 strains
belonging to five phylogenetic groups: Alpha- and Gammaproteobacteria, Bacillus-Clostridium group, Actinobacteria, and
Bacteroidetes were highlighted in the sea ice of the Spitzberg;
Gammaproteobacteria dominate the ecosystem. All strains are
psychrophilic (broadly defined) with a maximum production
of extracellular enzymes between 4 and 10
C. Active bacteria
up to À20
C have been identified in the sea ice of the Arctic.
In Antarctica, 100 distinct phylotypes were identified with
a distribution similar to that encountered in the Arctic ice.
They
include
Alphaand
Gammaproteobacteria,
Bacteroidetes, Gram-positive bacteria, and members of the
orders Chlamydiales and Verrucomicrobiales.
10.2.3.4 Snow and Glaciers
Snow and glaciers are interrelated ecosystems as ice-glacier
formed from snow by natural compression. The majority of
glaciers is found in Greenland and Antarctica and contain
about 80 % of the freshwater on the planet; their thickness
varies from a few tens of meters to 4 km. Although the low
salinity of freshwater is not conducive to the formation of
liquid jets, they do exist and their diameters vary from 1 μm
at about À50
C to 10 μm at 2
C (Price 2007). Other liquid
films form on the surface of insoluble mineral grains and
generate liquid inclusions hosting an abundant bacterial life.
The number of cells is on average between 10
2 and
10
4 mL
À1 ice, but in the basal region in contact with the
ground highly charged in minerals, cell densities can reach
10
9 mL
À1 . It was also demonstrated that the supply of
organic carbon in liquid veins would maintain a population
of 10–100 cells.mL
À1 for 400,000 years with possible
356
J.-L. Cayol et al.
promising.
10.2.3.1 Arctic and Antarctic Oceans
In these environments, below 60
south latitude, the temperature of the water varies between À1.9 and 5
C. The selection
pressure is high due to the relative stability of these
temperatures as compared to the same latitude terrestrial
environments. In the Arctic Ocean, below the permanent ice,
densities of 10
2 mL
À1 of heterotrophic bacteria have been
reported. Populations do not appear very different when comparing the Arctic to the Antarctic; so at the two poles, Alphaand Gammaproteobacteria and Bacteroidetes dominate with
97 % of the phylotypes identified being common to Arctic and
Antarctic. In Antarctica a large fluctuation of marine biomass
depending on the season, which reflects changes in temperature and light, is observed. Large populations of Flavobacteria
whose abundance is connected with chlorophyll and nutrients
are found on surface. Archaea are also abundant and represent
about 30 % of the biomass of prokaryotes. The most common
types of bacteria found in Arctic and Antarctic seawaters are
Alteromonas Colwellia, Glaciecola, Pseudoalteromonas,
Shewanella, and Polaribacter.
10.2.3.2 Deep Waters
Sixty percent of the Earth’s surface is covered by seas deeper
than 1,000 m. The hydrostatic pressure of these
environments is more than 110 MPa and temperatures
often below 4
C (except in hydrothermal vents where temperature can reach 370
C). Microorganisms capable of
withstanding these pressures and temperatures are called
psychropiezophiles. The first bacterium of this type was
discovered in 1979. It is a Spirillum-like bacterium (strain
CNPT-3) that grows well at 50 MPa and is unable to grow at
atmospheric pressure. Numerous psychropiezophilic bacteria have been isolated and characterized. It turns out that
they all belong to the group of Gammaproteobacteria
according to the classification based on the sequences of
16S and 5S rRNA genes. These bacteria are divided into
five predominant genera: Photobacterium, Colwellia,
Moritella, Shewanella, and Psychromonas. Regardless of
the type to which these bacteria belong, their membranes
have a high rate of unsaturated fatty acids to maintain fluidity at low temperature and high pressure as well. Depending
on genus to which bacteria belong, they also produce
long-chain polyunsaturated fatty acids including
eicosapentaenoic acid and/or docosahexaenoic acid (cf.
Sect. 17.7.8). The proportion of these polyunsaturated fatty
acids in the membrane varies between 50 and 70 %. However, production of these fatty acids does not seem to be
required for growth of psychropiezophiles. As an example,
Psychromonas profunda strain SS9 only produces monounsaturated fatty acids.
10.2.3.3 Sea Ice
Sea ice represents a particular habitat (Fig. 10.1) because of
temperature possibly dropping to À35
C and its semisolid
state. Its formation causes the expulsion of the dissolved salts
of the solid matrix but also the formation of a labyrinth with
liquid veins varying with temperature. Salinity can reach a
value of 14.5 % at À10
C compared to a value of 3.4 %
observed at À1.9
C. A very large concentration of dissolved
organic matter (DOM) is recorded, which transforms these
veins in habitats where many microorganisms develop. The
composition of these veins is not constant, resulting in a
desalination process increasing with the age of ice. Temperature gradients also exist within it, from the surface to the icewater interface, which makes this habitat a particularly heterogeneous environment. The total areas of these liquid streams
are of the magnitude order of 0.6–4.0 m
2 kg
À1 of ice. Heterotrophic bacteria are the main groups of prokaryotes detected.
They are psychrotrophic but also halotolerant; cyanobacteria
are also present. Unlike free waters, archaea are poorly
represented with about 0–3 % of total cells. The presence of
exopolysaccharides produced by microorganisms may act as
cryoprotectants but also as nutrient traps (see below) thus
favoring the colonization of habitats. More than 100 strains
belonging to five phylogenetic groups: Alpha- and Gammaproteobacteria, Bacillus-Clostridium group, Actinobacteria, and
Bacteroidetes were highlighted in the sea ice of the Spitzberg;
Gammaproteobacteria dominate the ecosystem. All strains are
psychrophilic (broadly defined) with a maximum production
of extracellular enzymes between 4 and 10
C. Active bacteria
up to À20
C have been identified in the sea ice of the Arctic.
In Antarctica, 100 distinct phylotypes were identified with
a distribution similar to that encountered in the Arctic ice.
They
include
Alphaand
Gammaproteobacteria,
Bacteroidetes, Gram-positive bacteria, and members of the
orders Chlamydiales and Verrucomicrobiales.
10.2.3.4 Snow and Glaciers
Snow and glaciers are interrelated ecosystems as ice-glacier
formed from snow by natural compression. The majority of
glaciers is found in Greenland and Antarctica and contain
about 80 % of the freshwater on the planet; their thickness
varies from a few tens of meters to 4 km. Although the low
salinity of freshwater is not conducive to the formation of
liquid jets, they do exist and their diameters vary from 1 μm
at about À50
C to 10 μm at 2
C (Price 2007). Other liquid
films form on the surface of insoluble mineral grains and
generate liquid inclusions hosting an abundant bacterial life.
The number of cells is on average between 10
2 and
10
4 mL
À1 ice, but in the basal region in contact with the
ground highly charged in minerals, cell densities can reach
10
9 mL
À1 . It was also demonstrated that the supply of
organic carbon in liquid veins would maintain a population
of 10–100 cells.mL
À1 for 400,000 years with possible
356
J.-L. Cayol et al.