2. Fatty Acids as Trophic and Chemical Markers
29
data). A report of the occurrence of 18:5(03 in the lipids of the cladocera Eurycercus lamellatus and Simocephalus vetulus from a small pond (Desvilettes et
aI., 1994) was rather unexpected, and it may have originated in the lipids of
Gymnodinium sp., a locally common phytoplankton species.
The fatty acid compositions and the relationship with the diet were studied in a
large number of species of aquatic and semiaquatic insects from diverse habitats
that use different feeding strategies (Hanson et aI., 1985). Arachidonic acid
(20:4(06) and 20:5(03 were among the major PUFA in most of the insects analyzed. The concentrations of 20:5(03 in the aquatic insects were larger than those
reported for terrestrial species (Dadd, 1983) and may represent an adaptation to
aquatic life. The analysis of lipids from aquatic insects also indicates that the
distribution of fatty acids markers of food sources differed predictably among
functional feeding groups (Hanson et aI., 1985). Filter-feeding species presented
the highest concentrations of 20:5(03 when compared with other feeding groups
such as shredders, gatherers, and predators. The high concentration of 20:5(03 in
the filterers obviously reflects the relative importance of diatoms in their diet.
2.4.3. Fatty Acid Composition of Bacteria
A comprehensive review of the lipid and fatty acid composition of bacteria can be
found in Ratledge and Wilkinson (1988). Bacterial fatty acids have been extensively studied, as evidenced by the large databases available on their lipid composition and chemotaxonomy (Boon et aI., 1996; Lechevalier, 1982). Bacterial
lipids and fatty acids have been used to assess biomass, taxonomic composition,
and physiological status (White, 1988; White et aI., 1979). Consequently, bacterial chemotaxonomy rapidly evolved as a very powerful tool with a wide range of
applications in classic bacteriology and microbial ecology. These applications
have created a demand for rapid and accurate methods for the identification of
bacteria and the development of automated GC-computerized systems for the
analysis of fatty acid composition of microorganisms (Haack et aI., 1994; Landry,
1994; Stead et aI., 1992; Moss, 1990). A detailed discussion of the occurrence and
distribution of fatty acids in bacteria is beyond the scope of this chapter, so a
summary of the principal fatty acids used as indicators of bacterial biomass will be
presented.
Lipids of gram-positive bacteria are concentrated in the plasma membrane,
whereas those of gram-negative bacteria have a greater complexity and consist of
an arrangement of neutral lipids and lipoproteins, embedded in the polysacharides
and proteins of the cytoplasm and the outer cellular envelope. Eubacteria can be
distinguished from archaebacteria due to the presence of acid-stable ether lipids in
the latest (Smith, 1988). There is a large structural variety in the fatty acids of
bacteria; different types of fatty acids markers used in microbial ecology are
presented in Table 2.3. Most bacterial fatty acids are either saturated or monounsaturated, including 16:0 and 16:1(07. Oleic acid (18:1(09) is present in bacteria,
but cis-vaccenic acid (18:1(07) is typically the dominant 18:1 isomer. The fatty
acids that make bacteria unique, however, are the hydroxy, cyclopropane, odd,
29
data). A report of the occurrence of 18:5(03 in the lipids of the cladocera Eurycercus lamellatus and Simocephalus vetulus from a small pond (Desvilettes et
aI., 1994) was rather unexpected, and it may have originated in the lipids of
Gymnodinium sp., a locally common phytoplankton species.
The fatty acid compositions and the relationship with the diet were studied in a
large number of species of aquatic and semiaquatic insects from diverse habitats
that use different feeding strategies (Hanson et aI., 1985). Arachidonic acid
(20:4(06) and 20:5(03 were among the major PUFA in most of the insects analyzed. The concentrations of 20:5(03 in the aquatic insects were larger than those
reported for terrestrial species (Dadd, 1983) and may represent an adaptation to
aquatic life. The analysis of lipids from aquatic insects also indicates that the
distribution of fatty acids markers of food sources differed predictably among
functional feeding groups (Hanson et aI., 1985). Filter-feeding species presented
the highest concentrations of 20:5(03 when compared with other feeding groups
such as shredders, gatherers, and predators. The high concentration of 20:5(03 in
the filterers obviously reflects the relative importance of diatoms in their diet.
2.4.3. Fatty Acid Composition of Bacteria
A comprehensive review of the lipid and fatty acid composition of bacteria can be
found in Ratledge and Wilkinson (1988). Bacterial fatty acids have been extensively studied, as evidenced by the large databases available on their lipid composition and chemotaxonomy (Boon et aI., 1996; Lechevalier, 1982). Bacterial
lipids and fatty acids have been used to assess biomass, taxonomic composition,
and physiological status (White, 1988; White et aI., 1979). Consequently, bacterial chemotaxonomy rapidly evolved as a very powerful tool with a wide range of
applications in classic bacteriology and microbial ecology. These applications
have created a demand for rapid and accurate methods for the identification of
bacteria and the development of automated GC-computerized systems for the
analysis of fatty acid composition of microorganisms (Haack et aI., 1994; Landry,
1994; Stead et aI., 1992; Moss, 1990). A detailed discussion of the occurrence and
distribution of fatty acids in bacteria is beyond the scope of this chapter, so a
summary of the principal fatty acids used as indicators of bacterial biomass will be
presented.
Lipids of gram-positive bacteria are concentrated in the plasma membrane,
whereas those of gram-negative bacteria have a greater complexity and consist of
an arrangement of neutral lipids and lipoproteins, embedded in the polysacharides
and proteins of the cytoplasm and the outer cellular envelope. Eubacteria can be
distinguished from archaebacteria due to the presence of acid-stable ether lipids in
the latest (Smith, 1988). There is a large structural variety in the fatty acids of
bacteria; different types of fatty acids markers used in microbial ecology are
presented in Table 2.3. Most bacterial fatty acids are either saturated or monounsaturated, including 16:0 and 16:1(07. Oleic acid (18:1(09) is present in bacteria,
but cis-vaccenic acid (18:1(07) is typically the dominant 18:1 isomer. The fatty
acids that make bacteria unique, however, are the hydroxy, cyclopropane, odd,