Figure 2.

Fe Reallocation to FeSOD during Transition to Fe Starvation.

Strain CC125 was grown in TAP medium with 18 μM Fe, washed, inoculated into TAP medium with 0 μM or 18 μM supplemental Fe (labeled −Fe and +Fe, respectively), and allowed to grow for 5 d.

(A) to (D) Comparison of cell density, measured by counting on a hemocytometer (A), chlorophyll content, measured spectrophotometrically (B), Fe content of cells (C), and spent media, measured by inductively coupled plasma–mass spectrometry (D). Data from three individual experiments are shown, represented by circles, triangles, and squares; chlorophyll content was calculated for a single experiment (the data series represented by square symbols in the other three panels).

(E) Abundance of MnSOD3 and hierarchy of Fe allocation. Soluble proteins (60 μg) were separated by nondenaturing gel electrophoresis and SODs visualized by activity staining (top panels for MnSOD3 and FeSOD). Total proteins (20 μg) were separated by denaturing gel electrophoresis and transferred to PVDF or nitrocellulose for immunoblot analysis.