148
ROBINA B. SCHOLES AND J. M. SHIEWAN
below 1000 m they are within the range 6’ to - 1.6OC. Finally, the
chemical compositions of many of the plants and animals are somewhat different from those on land. Thus, sea weeds contain large
amounts of alginates in their structural elements, and chitin, in the
form of lobster, crab and other crustacean shells, is very much more
abundant than on land. It is not surprising, therefore, that in the sea
microorganisms are found adapted to both the peculiar physical and
chemical conditions of their environment and some of these will now be
considered in more detail.
A. Halophiles
Bacteria and other organisms capable of growing in natural environments containing high salt concentrations, such as exist in the
Dead Sea and the Great Salt Lake have long been known (see Larsen,
1962). Richter (1928), however, was the first to show that certain
marine bacteria not only tolerated high salt concentrations but had a
specific requirement for salt. The term chlorophilic ” was first used
to describe these microorganisms by Le Dantec (1906), but the more
usual term now applied i s “ halophilic ” or I‘ salt Ioving ”.
All bacteria, on the basis of their tolerance or requirement for
sodium chloride, can be divided into three main groups (Shewan, 1942).
(1) The salt-sensitive or halophobic group, i.e. those which are killed
or suffer restricted growth in salt contents up to 8%. This includes most
pathogens, coliforms ” and anaerobes.
(2) The halotolerant group, which can grow in salt concentrations
between 0 and saturation (32% NaC1) and are often stimulated in low
concentrations ; this group comprises mainly micrococci and aerobic
spore bearers.
(3) The halophiles, requiring from 2% to 32% salt. These are sometimes further subdivided into the slight (2 to 5% NaCl); moderat@
(6 to 20%), and extreme halophiles (20 to 30%) (see also Larsen, 1962).
The rather extensive literature on the halophiles has been reviewed
by Weber (1949), Flannery (1966) and Ingram (1967) and more recently
and very thoroughly by Larsen (1962).
The extreme halophiles are usually characterized by the production
of an intense red or pink pigment, said to protect them fiom the bright
sunlight of their natural environment (Larsen, 1962), hence known a
the “ red ” or pink )’ halophiles ; and by the extreme pleomorphism
of their cells (Klebahn, 1919). They have been isolated from natural
wafers and soils (Hof, 1936) ; but are most often encountered in solm
salts and in salted products such as salt fish or salted hides (Lochhead,
1034) for the preparation of which such salf8 are used. They comprise
ROBINA B. SCHOLES AND J. M. SHIEWAN
below 1000 m they are within the range 6’ to - 1.6OC. Finally, the
chemical compositions of many of the plants and animals are somewhat different from those on land. Thus, sea weeds contain large
amounts of alginates in their structural elements, and chitin, in the
form of lobster, crab and other crustacean shells, is very much more
abundant than on land. It is not surprising, therefore, that in the sea
microorganisms are found adapted to both the peculiar physical and
chemical conditions of their environment and some of these will now be
considered in more detail.
A. Halophiles
Bacteria and other organisms capable of growing in natural environments containing high salt concentrations, such as exist in the
Dead Sea and the Great Salt Lake have long been known (see Larsen,
1962). Richter (1928), however, was the first to show that certain
marine bacteria not only tolerated high salt concentrations but had a
specific requirement for salt. The term chlorophilic ” was first used
to describe these microorganisms by Le Dantec (1906), but the more
usual term now applied i s “ halophilic ” or I‘ salt Ioving ”.
All bacteria, on the basis of their tolerance or requirement for
sodium chloride, can be divided into three main groups (Shewan, 1942).
(1) The salt-sensitive or halophobic group, i.e. those which are killed
or suffer restricted growth in salt contents up to 8%. This includes most
pathogens, coliforms ” and anaerobes.
(2) The halotolerant group, which can grow in salt concentrations
between 0 and saturation (32% NaC1) and are often stimulated in low
concentrations ; this group comprises mainly micrococci and aerobic
spore bearers.
(3) The halophiles, requiring from 2% to 32% salt. These are sometimes further subdivided into the slight (2 to 5% NaCl); moderat@
(6 to 20%), and extreme halophiles (20 to 30%) (see also Larsen, 1962).
The rather extensive literature on the halophiles has been reviewed
by Weber (1949), Flannery (1966) and Ingram (1967) and more recently
and very thoroughly by Larsen (1962).
The extreme halophiles are usually characterized by the production
of an intense red or pink pigment, said to protect them fiom the bright
sunlight of their natural environment (Larsen, 1962), hence known a
the “ red ” or pink )’ halophiles ; and by the extreme pleomorphism
of their cells (Klebahn, 1919). They have been isolated from natural
wafers and soils (Hof, 1936) ; but are most often encountered in solm
salts and in salted products such as salt fish or salted hides (Lochhead,
1034) for the preparation of which such salf8 are used. They comprise