FIG. 4.

Nondenaturing electrophoresis of periplasmic extracts (50 μg of protein) of R. sphaeroides f. sp. denitrificans grown under phototrophic conditions. Added to 18-h grown cultures were 0, 0.1, or 1 mM NaNO₂ or 20 mM KNO₃ or N₂O. Cell extracts were prepared 5 h after addition of the N oxides. Gels were stained for nitrate (A), nitrite (B), and N₂O (C) reductase activities with dithionite-reduced methyl viologen as the electron donor.