Abstract
Lipids comprise a large group of chemically heterogeneous compounds. The majority have fatty acids (FA) as part of their structure, making these compounds suitable tools to examine processes raging from cellular to macroscopic levels of organization. Among the multiple roles of FA, they have structural functions as constituents of phospholipids which are the “building blocks” of cell membranes; as part of neutral lipids FA serve as storage materials in cells; and FA derivatives are involved in cell signalling. Studies on FA and their metabolism are important in numerous research fields, including biology, bacteriology, ecology, human nutrition and health. Specific FA and their ratios in cellular membranes may be used as biomarkers to enable the identification of organisms, to study adaptation of bacterial cells to toxic compounds and environmental conditions and to disclose food web connections. In this review, we discuss the various roles of FA in prokaryotes and eukaryotes and highlight the application of FA analysis to elucidate ecological mechanisms. We briefly describe FA synthesis; analyse the role of FA as modulators of cell membrane properties and FA ability to store and supply energy to cells; and inspect the role of polyunsaturated FA (PUFA) and the suitability of using FA as biomarkers of organisms.
Highlights
Photosynthetic marine and freshwater microalgae, heterotrophic protists and bacteria have been considered to be the producers of natural ω3 long-chain (≥20 carbons) polyunsaturated fatty acids (PUFA), because they possess the key enzymes including methyl-end desaturases necessary for their de novo synthesis [16,17,18,19,20,21]
A relation between the ability to produce polyunsaturated FA (PUFA) and psychrophilic and/or piezophilic growth strongly suggest a role of PUFA in bacterial membrane adaptation, a mutant of Photobacterium profundum unable to produce PUFA could grow under high pressure and low temperature conditions [100]
Wax esters, formed by a FA and a fatty alcohol linked by an ester bond, are produced by several bacterial species when grown on substrates such as hydrocarbons, alkanols and fatty acids under nitrogen-limiting conditions [113,114,115]
Summary
Fatty acids (FA), as part of molecules or acting individually, have diverse functions in cells that range from structural “building blocks” of cell membranes to suppliers of energy and signalling molecules (Table 1). Photosynthetic marine and freshwater microalgae, heterotrophic protists and bacteria have been considered to be the producers of natural ω3 long-chain (≥20 carbons) polyunsaturated fatty acids (PUFA), because they possess the key enzymes including methyl-end (or “ωx”) desaturases necessary for their de novo synthesis [16,17,18,19,20,21]. Recent studies have identified 121 ωx desaturase sequences from 80 species within various invertebrate taxa suggesting that, in addition to trophic upgrading, de novo synthesis of PUFA is possible in some invertebrates [22,23] These studies point to the need of a major revision in the scientific understanding of ω3 long-chain PUFA production in global food webs.
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