Fig. S5.

Aerobic utilization of formate or nitrite by N. moscoviensis. (A) Aerobic use of formate with O₂ as terminal electron acceptor by a pure culture of N. moscoviensis. Data points show the means of biological replicates (n = 3). Error bars represent SD and are not shown if smaller than symbols. This experiment represents an independent replication of the experiment shown in Fig. 3B. (B) Aerobic use of nitrite with O₂ as terminal electron acceptor by a pure culture of N. moscoviensis. Data points show the means of biological replicates (n = 3). Error bars represent SD and are not shown if smaller than symbols. This experiment was performed with the same amount of biomass from the same inoculum as the experiment in A. (C) Aerobic growth of N. moscoviensis on formate or nitrite, respectively. Data points show the means of biological replicates (n = 3). Error bars represent SD and are not shown if smaller than symbols. Total biomass protein was measured during the incubations shown in A and B to follow the growth of the cultures in these experiments. In the control experiment, the same amount of N. moscoviensis biomass was incubated in mineral medium without addition of formate or nitrite. Here, total protein decreased likely because of endogenous respiration in the absence of any external electron donor. (D) Long-term incubation of N. moscoviensis with formate and nitrate under oxic conditions. The initial concentrations of formate and nitrate were 5 mM and 0.5 mM, respectively. This graph shows the formate concentration in the culture supernatant. The results of two biological replicates are shown. (E) Nitrite concentrations in the culture supernatant during the incubation experiment shown in D. The initial net increase of the nitrite concentration was caused by nitrate reduction. The following net decrease of nitrite demonstrates the concomitant utilization of nitrite and formate (also see D) from day 6 to the end of the experiment. The results of two biological replicates are shown. (F) Nitrate concentrations in the culture supernatant during the incubation experiment shown in D and E. The initial net decrease and subsequent net increase of the nitrate concentration are consistent with the nitrate-reducing and nitrite-oxidizing activities (D and E) of N. moscoviensis in this experiment. (G) Nitrite oxidation by N. moscoviensis in absence of formate. The rate of nitrite oxidation was considerably higher than in presence of formate (E). Highly similar amounts of N. moscoviensis biomass were used in these incubation experiments (D–G).