Article Figures & Data
Figures
- FIG. 1.
A steady-state culture of G. sulfurreducens growing at a dilution rate of 0.05 h−1 with fumarate as the terminal electron acceptor was pulsed with 10 mM Fe(III) citrate (arrow). The response of the cell to the pulse was monitored by analyzing the respective respiration products, succinate (filled circles) and Fe(II) (open circles). All the Fe(II) produced was finally washed out of the chemostat as expected in a continuous culture system. Cells were harvested before the Fe(III) pulse, after the Fe(III) pulse (6 h), and when all the Fe(III) was fully reduced to Fe(II) (14 h). RNA was isolated from those cells, and Northern blot hybridization was performed with a specific oligoprobe for frdC (fumarate reductase). The detected transcript corresponds with the 3.3 kb of the frdCAB operon. As a control, parallel cultures were pulsed with the chelating agent citrate, and Northern analysis was performed as described for the Fe(III) citrate pulse.
- FIG. 2.
(A) Effect of terminal electron acceptors on the growth yield. Cells of G. sulfurreducens were cultured in chemostats in the presence of fumarate, fumarate and Fe(III), or just Fe(III) as the terminal electron acceptor. The results shown are the means of results from triplicate cultures for each treatment. (B) Effect of the terminal electron acceptor on fumarate reductase (frdCAB) expression. Northern blot hybridizations on isolated RNA were performed with a specific oligoprobe for frdC. fum, fumarate.
- FIG. 3.
(A) Scheme of fumarate transformation by G. sulfurreducens in the presence of Fe(III). Fumarate is transformed into malate when fumarate respiration is inhibited. Malate is subsequently converted to acetyl coenzyme A (CoA) via pyruvate with the release of formate. TCA, tricarboxylic acid; e−, electron. (B) Malate (filled circles) and formate (open triangles) formation after a pulse of 10 mM Fe(III) citrate. The reduction of Fe(III) is plotted as Fe(II) production (open circles).
