BIOSYNTHESIS AND DIETARY UPTAKE OF POLYUNSATURATED FATTY ACIDS IN PIEZOPHILIC BACTERIA

This study was undertaken to asses the importance of polyunsaturated fatty acids (PUFAs) in the growth of piezophilic bacteria under high hydrostatic pressure conditions, by examining the cellular uptake of arachidonic acid and the biosynthesis of PUFAs. A moderately piezophilic (Shewanella violacea DSS12) and two hyperpiezophilic bacteria (S. benthica DB21MT-2 and Moritella yayanosii DB21MT-5) were grown under 50 MPa (megapascal) and 100 MPa, respectively, on media containing marine broth (MB) 2216, MB 2216 with arachidonic acid (AA, sodium salt), and MB 2216 with AA and antibiotic cerulenin. The three piezophilic strains exhibited typical phospholipid fatty acid (PLFA) profiles dominated by unsaturated fatty acids (50 to 67% of the total fatty acids). There was active uptake and cellular incorporation of AA in the two hyperpiezophilic bacteria DB21MT-2 (14.7%) and DB21MT-5 (1.4%), but no uptake was observed in DSS12. When cells were treated with antibiotic cerulenin, all three strains incorporated AA into cell membranes (13 to 19%). Concurrently, the concentrations of EPA in DSS12 and DHA in DB21MT-5 increased, whereas the concentration of EPA in DB21MT-2. The biosynthesis of even-numbered monounsaturated fatty acids was significantly inhibited (10 to 37%), whereas the concentrations of PUFAs increased by 2-4 times. These results suggest that polyunsaturated fatty acids are required for growth and piezoadaptation for the piezophilic strains tested in this study.