Fig. 3: Schematic of NO production and phototroph inhibition by NO via three mechanisms of nitrate-reducing Fe(II) oxidation.
From: Inhibition of phototrophic iron oxidation by nitric oxide in ferruginous environments
a, The Fe(II) oxidizer of culture KS (Gallionella) produces NO via denitrification coupled with enzymatic Fe(II) oxidation. Some NO may be scavenged by the heterotrophic partner strains (dominated by Bradyrhizobium), although this is probably limited by carbon availability. Remaining NO could interact with the phototroph causing inhibition. It is also possible that some NO reacts with Fe(II) abiotically in this scenario. The measured NO concentrations reflect the balance of these competing production and consumption pathways. Importantly, our model does not simulate the individual contribution of the components of the KS culture but models the culture as a whole. Corg, organic carbon. b, Fe(II) oxidation by Acidovorax sp. BoFeN1 produces NO2− during heterotrophic denitrification, which oxidizes Fe(II) abiotically and produces NO. c, Nitrite reacts abiotically with Fe(II) and produces NO. In all cases, the NO produced inhibits photoferrotrophic activity.
