Moorella thermoacetica (originally isolated as Clostridium thermoaceticum) has served as the primary acetogenic bacterium for the resolution of the acetyl coenzyme A (acetyl-CoA) orWood–Ljungdahl pathway, a metabolic pathway that (i) autotrophically assimilates CO2 and (ii) is centrally important to the turnover of carbon in many habitats. The purpose of this article is to highlight the diverse physiological features of this model acetogen and to examine some of the consequences of its metabolic capabilities.