Marine lipids
Different approaches can be applied in this research field: searching
for new fatty acid structures, evaluating new sources of polyunsaturated
fatty acids of biological interest and their role in cell membrane, investigating biosynthetic pathways, and developing biomarkers to detect
microorganisms and for chemotaxonomic purposes.
Our studies began with sponge phospholipids and were extended to lipids
of gorgonians, algae and tropical fishes. They are now mainly concerned
with glycolipids from marine invertebrates.
Sponges were collected by hand at low tide or by scuba diving (depths
of 10-45 m) along or off the coast of Senegal, New Caledonia, Australia,
Qatar and Brittany. The gorgonian Leptogorgiapiccola (two morphs) was
collected off the Senegalese coast. The red alga was collected on the
eastern coast of Sicily.
Results and discussion
Phospholipid fatty acids and cell membrane properties
Cell membrane permeability appears to be highly dependent on fatty
acid composition and can be described through a matrix constructed
with all possible combinations of chain lengths and double bonds
(Litchfield & Morales, 1976). This was originally done with major
fatty acids occurring in more than 30 organisms, half of which were
marine ones. The major fatty acids usually found in membranes ol
living organisms all fall into a central region, namely the “region of feasible adaptations”. Increasing the number of carbons or lowering the
number of double bonds makes the lipid bilayer more rigid. However,
marine sponges appear to be an exception to this rule.
Major sponge phospholipid fatty acids, including very low amounts of
the usual polyunsaturated fatty acids, but high levels of C24 to C30
chains (representing up to 80%), fall outside the central region (Bergmann & Swift, 1951; Litchfield & Morales, 1976). The fatty acid composition can vary considerably with temperature, relative to adaptation
to the environment, as recently observed in the case of gorgonians
(Mirallès et al., 1995).
Isoprenoid fatty acids from sponge phospholipids
In each sponge phospholipid studied in this work, about 70 fatty acids
were identified as methyl esters and N-acyl pyrrolidides by GC/MS. An
interesting finding was the co-occurrence of two isoprenoid fatty acids
in sponge phospholipids of the genus Cinachyrella: 4,8,12-trimethyltridecanoic acid (4,8,12-TM-13:0) is a frequent marine fatty acid,
whereas 5,9,1 3-trimethyltetradecanoic acid (5,9,13-TM-l4:0) is a quite
rare fatty acid in nature (table 1).
36
Different approaches can be applied in this research field: searching
for new fatty acid structures, evaluating new sources of polyunsaturated
fatty acids of biological interest and their role in cell membrane, investigating biosynthetic pathways, and developing biomarkers to detect
microorganisms and for chemotaxonomic purposes.
Our studies began with sponge phospholipids and were extended to lipids
of gorgonians, algae and tropical fishes. They are now mainly concerned
with glycolipids from marine invertebrates.
Sponges were collected by hand at low tide or by scuba diving (depths
of 10-45 m) along or off the coast of Senegal, New Caledonia, Australia,
Qatar and Brittany. The gorgonian Leptogorgiapiccola (two morphs) was
collected off the Senegalese coast. The red alga was collected on the
eastern coast of Sicily.
Results and discussion
Phospholipid fatty acids and cell membrane properties
Cell membrane permeability appears to be highly dependent on fatty
acid composition and can be described through a matrix constructed
with all possible combinations of chain lengths and double bonds
(Litchfield & Morales, 1976). This was originally done with major
fatty acids occurring in more than 30 organisms, half of which were
marine ones. The major fatty acids usually found in membranes ol
living organisms all fall into a central region, namely the “region of feasible adaptations”. Increasing the number of carbons or lowering the
number of double bonds makes the lipid bilayer more rigid. However,
marine sponges appear to be an exception to this rule.
Major sponge phospholipid fatty acids, including very low amounts of
the usual polyunsaturated fatty acids, but high levels of C24 to C30
chains (representing up to 80%), fall outside the central region (Bergmann & Swift, 1951; Litchfield & Morales, 1976). The fatty acid composition can vary considerably with temperature, relative to adaptation
to the environment, as recently observed in the case of gorgonians
(Mirallès et al., 1995).
Isoprenoid fatty acids from sponge phospholipids
In each sponge phospholipid studied in this work, about 70 fatty acids
were identified as methyl esters and N-acyl pyrrolidides by GC/MS. An
interesting finding was the co-occurrence of two isoprenoid fatty acids
in sponge phospholipids of the genus Cinachyrella: 4,8,12-trimethyltridecanoic acid (4,8,12-TM-13:0) is a frequent marine fatty acid,
whereas 5,9,1 3-trimethyltetradecanoic acid (5,9,13-TM-l4:0) is a quite
rare fatty acid in nature (table 1).
36