PMC

Growth dynamics of S. oneidensis MR-1 and selected mutants in anaerobic M1 medium supplemented with 20 mM lactate and 30 mM fumarate. Some error bars are smaller than the symbols.

Schematic representation of the proposed spatial localization of enzymes involved in pyruvate reduction. According to the proposed scheme, protons resulting from formate oxidation remain in the periplasm, whereas electrons through the electron transport chain are moved toward Dld-II and used in a reaction of pyruvate reduction, with the latter accompanied by the consumption of two protons in the cytoplasm. This process may therefore lead to PMF generation. Dld-II, oxidative d-lactate dehydrogenase; FDH, formate dehydrogenase.

Metabolic pathways implicated in pyruvate fermentation by S. oneidensis MR-1. FDH stands for one or more formate dehydrogenases encoded in the MR-1 genome (SO_0101 to SO_0103, SO_4508 to SO_4511, and SO_4512 to SO_4515). LdhA (SO_0968), fermentative lactate dehydrogenase; PDH (SO_0424 to SO_0426), pyruvate dehydrogenase complex; PflB (SO_2912), pyruvate formate-lyase; Pta (SO_2916), phosphotransacetylase; AckA (SO_2915), acetate kinase; Hyd (SO_3920 and SO_3921) and Hya (SO_2098 and SO_2099), [Fe-Fe] and [Ni-Fe] hydrogenases, respectively. The scheme reflects the predicted localizations of the corresponding enzymes.

Effects of gene deletions on S. oneidensis MR-1 growth (A) and acetate accumulation (B) under O₂-limited conditions in M1 medium supplemented with 90 mM sodium lactate as the sole source of carbon. Experiments were run in controlled bioreactors (see Materials and Methods for details). Samples for data presented here were taken at 16.5 to 17 h after the O₂ limitation phase started. Growth was measured as the optical density at 600 nm. The results are representative of a typical experiment. Experiments were repeated twice, and standard deviations did not exceed 8%.