The Wood-Ljungdahl pathway of CO2 fixation is a stepwise process that involves the synthesis of acetate from CO2. This pathway has been extensively studied due to its importance in acetogenesis, the conversion of CO2 to acetate by acetogenic bacteria. The pathway consists of two branches: the Eastern branch, which reduces CO2 to a methyl group, and the Western branch, which reduces CO2 to carbon monoxide and then condenses it with the methyl group to form acetyl-CoA. The pathway is crucial for energy conservation and carbon assimilation in acetogens, and it is also used by methanogens for CO2 fixation. Key components and steps of the pathway have been identified through various biochemical, biophysical, and bioinorganic techniques. The pathway involves enzymes such as formate dehydrogenase, acetyl-CoA synthase, and methyltransferase, and cofactors like H4 folate, cobalamin, and nickel-iron-sulfur clusters. The pathway's importance extends to its role in the emergence and early evolution of life, as it may have been the first autotrophic metabolism. The genome sequencing of *Moorella thermoacetica* has provided insights into the genes and pathways involved in acetogenesis, highlighting the widespread distribution of acetogenic traits across different phyla.The Wood-Ljungdahl pathway of CO2 fixation is a stepwise process that involves the synthesis of acetate from CO2. This pathway has been extensively studied due to its importance in acetogenesis, the conversion of CO2 to acetate by acetogenic bacteria. The pathway consists of two branches: the Eastern branch, which reduces CO2 to a methyl group, and the Western branch, which reduces CO2 to carbon monoxide and then condenses it with the methyl group to form acetyl-CoA. The pathway is crucial for energy conservation and carbon assimilation in acetogens, and it is also used by methanogens for CO2 fixation. Key components and steps of the pathway have been identified through various biochemical, biophysical, and bioinorganic techniques. The pathway involves enzymes such as formate dehydrogenase, acetyl-CoA synthase, and methyltransferase, and cofactors like H4 folate, cobalamin, and nickel-iron-sulfur clusters. The pathway's importance extends to its role in the emergence and early evolution of life, as it may have been the first autotrophic metabolism. The genome sequencing of *Moorella thermoacetica* has provided insights into the genes and pathways involved in acetogenesis, highlighting the widespread distribution of acetogenic traits across different phyla.