Figure 2.
Photosynthetic activity and lipid accumulation in the Pt1 ecotype of P. tricornutum cultivated in replete or N- or P-depleted conditions. A, Time-course evolution of photosynthetic efficiency. The Fv/Fm ratio, representative of the photosynthetic efficiency of the diatom, was measured for Pt1 cells grown either in a replete medium (10N10P; black) or in medium deprived of N (0N10P; blue) or P (10N0P; red). B, Nonpolar lipid accumulation measured at day 13. Nonpolar lipid accumulation was estimated by Nile Red fluorescence normalized to cell number. In 10N10P, the fluorescence signal remained at background level, indicating that the Fv/Fm decrease was not due to N or P starvation. r.f.u., Relative fluorescence units. C, Total glycerolipid accumulation. The total level of glycerolipids (membrane lipids + TAG) was estimated by the total FA content after 5 d of cultivation in the replete condition (black bar) or following N starvation (red bar) or 13 d of P starvation (blue bar). To avoid any N deficiency in 10N10P or 10N0P culture, the media were replaced by fresh ESAW 10N10P medium every 3 d.