Figure 3. The reconstructed TCA-cycle and CO₂ fixation pathway of Dehalococcoides.

The arrows show the directionality of the reactions. (A) Grey: citrate synthase gene currently not identified in iAI549, but the pathway is suggested to be present by Tang et al. [84]; Orange: pathways for which homologous putative genes (∼30% amino acid sequence identity) were tentatively identified in Dehalococcoides, but are suggested to be absent by Tang et al. [84]; Red: pathways for which putative genes are confirmed to be present by both iAI549 and Tang et al. [84]. In all cases, the TCA-cycle of Dehalococcoides is not closed which explains their inability to use acetate as an energy source. (B) Dehalococcoides' requirement of CO₂ in addition to acetate for their in silico growth. The numbers are flux values in mmol.gDCW⁻¹.h⁻¹. During pyruvate synthesis, Dehalococcoides require 67% carbon (molar basis) from acetate and 33% (molar basis) from CO₂. Thus, Dehalococcoides fix carbon via the pyruvate-ferredoxin oxidoreductase or pyruvate synthase (POR) pathway.