Fig. 5
An overview of the potential metabolic fate of 13CO2 during the TCA cycle, cellular protein biosynthesis, nucleotide biosynthesis, and the impact on fatty acid production in transgenic E. coli K12 strains expressed (a) KOR or (b) KOR with ACL compared to vector control strain, respectively. A two-tailed t-test was used for statistical analysis, **** indicates p < 0.005 (highly statistically significantly difference); *** indicates p < 0.01; ** indicates p < 0.05 (statistically significantly difference); * indicates p < 0.1 (borderline statistically significantly difference). Two heterologous enzymes, KOR and ACL, play distinct roles in this carbon fixing system. KOR primarily fixes CO2 through the rTCA cycle, maintaining carbon flow within the TCA cycle. ACL further redirects and shifts the carbon flux of CO2 out of TCA cycle towards cellular protein and nucleotide biosynthesis. Metabolites from carbohydrate and TCA cycle are denoted in black, amino acids in blue, fatty acids in orange, and labeled 13CO2 in red. Hetero-expressed enzymes, KOR and ACL, are represented in purple and yellow, respectively. (SAFA: saturated fatty acids; MUFA: mono-unsaturated fatty acids; TFA: total fatty acid; PPRP: phosphoribosyl pyrophosphate; dC: deoxycytidine; dT: deoxythymidine; dG: deoxyguanosine; dA: deoxyadenosine)