1. Teichoic acid was isolated by extraction with trichloroacetic acid of the membrane fraction of disrupted cells of Staphylococcus lactis I3. 2. The purified material contains glycerol, phosphate and alanine, but little or no sugar or amino sugar. 3. A study of the products of hydrolysis with acid and alkali established that the membrane teichoic acid is a (1→3)-linked poly(glycerol phosphate) that differs in structure from the glycerol teichoic acid in the wall of this organism. 4. The alanine ester residues show the characteristic high lability to alkali and are thus distinguishable from the more stable alanine ester residues of the wall teichoic acid. 5. The significance of these structural features and the possible function of teichoic acids are discussed.
