• Antarctic;
  • Psychrophile;
  • Eicosapentaenoic acid;
  • Arachidonic acid


A psychrophilic bacterium, designated strain 651, was isolated from Antarctic sea ice collected from Prydz Bay, Eastern Antarctica. The fatty acid composition of the strain was characteristic of the Flavobacterium-Cytophaga-Microscillia group. The bacterium also produced 12.2–2.6% eicosapentaenoic acid (20:5ω3) and 1.4–2.7% arachidonic acid (20:4ω6). To our knowledge this is the first report of a bacterium that contains elevated proportions of both fatty acids. The proportion of eicosapentaenoic acid responded to growth temperature in a linear manner over the temperature range 2–15°C while the percentage of arachidonic acid remained relatively unchanged. Eicosapentaenoic acid appears to modulate both lipid phase and fluidity in response to temperature within the cellular membrane of strain 651, while arachidonic acid does not appear to be involved in this response. Further study of the polyunsaturated fatty acid biosynthetic mechanisms of strain 651 may yield significant information regarding the relationship between prokaryotic and eukaryotic polyunsaturated fatty acid biosynthesis.