Fig. 3

Characterization of the Nile red staining. a Biomass specific lipid fluorescence. After an initial linear correlation, the fluorescence signal saturates above a biovolume of 0.2 µL mL⁻¹ for both cell types (dashed line). b Time-dependent staining kinetics of cells with a biovolume of 0.15 µL mL⁻¹. In contrast to staining growing cells containing low levels of lipids (0.5 h), non-growing cells with high lipid content need significantly more time (2 h) for quantitative staining. Cells were stained in 25 % (v v⁻¹) DMSO containing 1 mg L⁻¹ Nile red at 40 °C, excitation at 480 nm. Error bars deviated from analytical replicates (n = 5)