FIG. 4.

(A) Reduction of Fe-beads by S. oneidensis MR-1 as a function of the preincubation conditions. MR-1 cells were preincubated with 1 mM fumarate (diamonds) or 1 mM ferric citrate (squares) or under oxygen-limited conditions (triangles). (B) Fe-bead reduction by anaerobically and aerobically grown MR-1 cells. Fumarate-grown cells were grown anaerobically with 10 mM fumarate as the electron acceptor, while aerobically grown cells were grown with oxygen as the electron acceptor. Chloramphenicol was added to separate Fe-bead cultures with these cells (+ Cm) to inhibit new protein synthesis. (C) Reduction of Fe-beads as a function of cell density. Serial dilutions of a standard high-density Fe-bead culture inoculum were incubated in separate tubes with Fe-beads. A linear fit to the data is shown. Each data point is the average for duplicate cultures (the error bars indicate the ranges) from 3 days of incubation with the Fe-beads.