FIG. 1.

Ferrihydrite reduction in growth experiments with S. deleyianum supplied with acetate, formate, ferrihydrite, and 0.01% inoculum. One of the following was added: cysteine (2 mM), cysteine (2 mM) plus thiosulfate (0.05 mM), or cystine (0.5 mg ml⁻¹). The inoculum had been grown with fumarate as the substrate and cysteine as the sulfur source. Means of two determinations are shown for duplicate experiments.