Figure 1. Acetone-butanol production plant in Peoria, USA, around 1925. Drawing based on a photograph published in: S.C. Beesch, Ind. Eng. Chem. 44, 1677 (1953). (Drawing: Anne Kemmling, Goettingen, Germany.)

Figure 2. Cells of a Sporomusa species carrying spores. (Photograph: Hans Hippe, Goettingen, Germany.)