FIG. 3.

Reduction of fumarate, DMSO, TMAO, and nitrite by MR-1 and SR-21. Cell extracts of MR-1 and SR-21 were separated by native PAGE and assayed for fumarate (A), DMSO (B), and TMAO (C) reductase activities. Benzyl viologen was used as the artificial electron donor. Clear bands in all samples indicate the ability of MR-1 and SR-21 to reduce these electron acceptors. (D) Nitrite reduction by MR-1 and SR-21 was assayed by monitoring the decrease in nitrite concentration in the medium. No differences were observed in the ability of SR-21 to use nitrite compared to the wild type.