Role of high percentage of poly unsaturated fatty acids in barophiles
Answers
The bulk of de novo biosynthesis of the two long-chained polyunsaturated fatty acids (PUFA) of the n–3 series, eicosapentaenoic (20:5 n–3; EPA) and docosahexaenoic (22:6 n–3; DHA) acid, is thought to take place among phototrophic algae at the base of the marine food web. From there, they are transferred through trophic levels and accumulated as major constituents of the lipids of practically all marine animals [1]. The presence of n–3 PUFA in heterotrophic prokaryotes was first reported by Johns and Perry [2] in the marine bacterium Flexibacter polymorphus. Later, EPA and DHA have been proved present in bacteria isolated from a number of cold marine habitats [3–9] and even from freshwater fish [10]. Several studies ascribe a particular function to these fatty acids in the microbes’ adaptation to low environmental temperatures. This is manifested by distinct reciprocal relationships between growth temperature and the percentage of PUFA present in the total fatty acids [3, 4, 11]. Hamamoto et al. [9] point to a hierarchy of cold adaptation, where the DHA producers generally show a more psychrophilic character than the EPA producers, whereas non-PUFA-producing psychrotrophic strains exhibit the highest maximum growth temperatures. A positive correlation between hydrostatic pressure and the percentage of PUFA in barophilic bacteria has also been demonstrated