Figure 3.

Iron binding to C. velia cells; temperature and time dependence. C. velia was grown in iron-free Mf medium, harvested, washed with iron-free Mf medium, and resuspended in the same medium at 0°C (circles) or 25°C (squares) in the presence of 0.5 μm ⁵⁵Fe(III)-citrate (1:20). At the times indicated, aliquots were taken and washed with Mf medium containing 1 mm citrate buffer. The amount of extracellular (black symbols) and intracellular (white symbols) iron specifically bound to the cells was determined by washing the cells with Mf medium containing EDTA, BPS, and desferrichrome (10 mm each). The difference between extracellular iron (washable by strong chelators) and intracellular iron (nonwashable) decreased with time only at 25°C (represented by Δ values on the figure). Means ± sd from three experiments are given.