Fig. 3.
Formate utilization by a pure culture of N. moscoviensis. (A) Anaerobic consumption of formate with nitrate as terminal electron acceptor. Nitrate was nearly stoichiometrically reduced to nitrite. No nitrite formation from nitrate was observed in the control experiment without formate. The results of two biological replicates are shown for all incubations. (B) Aerobic use of formate with O2 as terminal electron acceptor. For the incubations with N. moscoviensis cells, the results of two biological replicates are shown. Please note that the control experiment with formate but without cells, which confirms the chemical stability of formate, was performed for these incubation conditions only. (C) Aerobic use of formate with both O2 and nitrate as terminal electron acceptors. The oxidation of the formed nitrite became detectable on the seventh day of incubation. Data points show the means of biological replicates (n = 3). Error bars represent SD and are not shown if smaller than symbols. An extended incubation experiment (23 d) confirming the concomitant utilization of formate and nitrite is shown in Fig. S5 D–F.