Cacao

Figure 3: The first sentence of the figure is “Nitrite-reducing properties of the NirS mutant HF384 grown anaer- obically on nitrate.” No where in the figure does it mention NarG or NapF. Maybe it would have been clearer if I originally worded my explanation this way: both the wild type, and mutant NirS genes were grown of nitrate. Both the wild type and the mutant was able to convert the nitrate to nitrite. However, the wild type NirS were able to reduce the nitrate into nitrogen oxidizes, while the NirS mutants could not. Because of this, nitrite built up in the medium. You can see this by looking at the figure. The black squares represented by the black squares and you can see a reduction of nitrite over time. On the other hand, the white triangles represent the NirS mutants and you can see a increase in nitrite over time since the mutants are unable to further reduce nitrite to nitrogen oxides.

Figure 3 does not talk about the mechanism by which nitrite is accumulated in the medium based on the conversion of nitrate to nitrite. Instead this figure shows that when external nitrite is added there is an increase in the genes narG and napF. There is no mention of nirS in this figure.