Lipoteichoic acid (LTA) and deacylated lipoteichoic acid were isolated from the bovine rumen Gram-negative anaerobe B. fibrisolvens by phenol extraction. Lipoteichoic acid (21.8 .mu.mol P/g cells) consisted of a conventional 1,3-phosphodiester-linked chain of glycerol phosphate units joined covalently to a glycolipid. It was not substituted with glycosyl or D-alanyl ester groups. Deacylated lipoteichoic acid (57.5 .mu.mol P/g cells) was similar in constitution but lacked fatty acid esters. Lipoteichoic acid reacted serologically with antisera to the glycerol phosphate backbone of known lipoteichoic acids. The presence of similar teichoic acid polymers was also demonstrated in some other strains of B. fibrisolvens and this is of significance in demonstrating that teichoic acids can occur in gram-negative bacteria.