Figure 1.

Mössbauer spectra of fermenting WT cells at varying pH (MM supplemented with 40 μM⁵⁷Fe^IIIcitrate and 10 μM CuSO₄).A, pH 7, B, pH 6, C, pH 5, D, pH 4, E, pH 3. Data are black hashmarks; composite simulations are the solid red lines. The green line simulates low-spin Fe^II hemes and [Fe₄S₄]²⁺ clusters. The blue line simulates nonheme high-spin Fe^II. The purple line simulates nonheme high-spin Fe^III. Individual simulations were combined to yield the composite simulation of of the WT pH 5 spectrum. MM, minimal medium.