FIG 4.

Moorella thermoacetica DSM 2955 grown on H₂/CO₂ (⬥), glucose alone (□), or glucose with nitrate (×). (A) δ¹³C values of the substrate (CO₂ or glucose) and the product (acetate). In the key, the different treatments—H₂/CO₂, glucose (Glu), and glucose plus nitrate (Glu + NO₃)—are given in parentheses. (B) Regression analysis of the respective incubations. The δ¹³C value of acetate reflects the stoichiometry of the producing pathway. For example, on glucose, two-thirds of the acetate released originates from glycolysis and decarboxylation (ε_Glu+NO3 = −0.4‰) and one-third from the acetyl-CoA pathway (ε_H2/CO2 = −55.8‰); the coordinated action of both pathways results in a mixed fractionation reflecting the contribution of each (ε = −18.5‰).