Phospholipid FA of piezophilic bacteria from the deep sea

Phospholipid FA (PLFA) profiles were determined on four piezophilic bacteria from the deep sea: Moritella japonica DSK1, Shewanella violacea DSS12, S. benthica DB6705, and S. benthica DB21 MT-2. The total concentrations of PLFA were higher in strains grown at low pressure (DSK1, 10 MPa, 27.0 mg/g dry wt cells; DSS12, 50 MPa, 24.0 mg/g), and lower in strains grown at high pressure (DB6705, 85 MPa, 1.9 mg/g; DB21MT-2, 100 MPa, 3.0 mg/g). The piezophilic bacteria were characterized by a high abundance of unsaturated FA (62-73% of total FA). In particular, PUFA were detected in all piezophiles examined. Moritella japonica DSK1 produced 22:6n-3 (DHA), whereas the three Shewanella strains produced 20:5n-3 (EPA) with trace amounts of DHA. The detection of low levels of the medium-chain-length PUFA 18:2n-6 and 18:3 (DSK1) and 20:2 (DB6705 and DB21MT-2) suggests that the biosynthesis of EPA and DHA may be regulated by the formation and desaturation of di- and tri-unsaturated FA.