FIG 7.

Oxidation of nitrite by biogenic manganese oxide (MnO_X) produced in cell-free culture supernatant of AzwK-3b. The figure shows the concentrations over time of nitrite (A) and nitrate (B), as determined by ion chromatography (note that concentrations were corrected for the IC peak from chloride, to account for evaporation during the experiment). As controls, samples without MnO_X (green) or with MnO₂ powder (orange) were included in the experiment (see Materials and Methods). The samples with AzwK-3b cell-free manganese oxide contained (from gray to black) 0.2, 0.5, 1, and 2 mM manganese oxide equivalent (see Materials and Methods).