In terms of lipid composition this is the best-studied group of the genus. Like most clostridia and indeed many bacteria, these species contain PE, PG and CL. C. acetobutylicum differs from the other two in having large amounts of glycosyl-diradylglycerols in addition to phospholipids (Johnston & Goldfine, 1992; Oulevey et al., 1986). A distinguishing feature of these species is the presence of significant levels of glycerol-acetals of plasmenylethanolamine (PlaE) (Matsumoto et al., 1971; Khuller & Goldfine, 1974) and smaller amounts of PGacetals of PlaE