RESUMEN
The lipid compositions of two spirochetes isolated from the human oral cavity and two isolated from pig feces were examined. These isolates were unusual in that they did not require long-chain fatty acids for growth, as do the other host-associated spirochetes, but rather required isobutyric and valeric acids. Therefore, they could be cultured in a medium free of serum or fatty acid - albumin supplements. The major fatty acids synthesized were normal and iso fatty acids with 14 and 16 carbons. No unsaturated fatty acids were detected, nor were chain lengths longer than 16 carbons. The major complex lipids found were monogalactosyl diglyceride, phosphatidyl glycerol, and bis-phosphatidyl glycerol. Nitrogenous phospholipids, present in Treponema and Leptospira, were not synthesized by these novel strains. The data indicate an intermediate position of these isolates between Treponema and free-living Spriochaeta.