Immunochemical studies on the lipoteichoic acids of Bifidobacterium bifidum subsp. pennsylvanicum

Antisera to lipoteichoic acid of Bifidobacterium bifidum subsp. pennsylvanicum were obtained by injecting lipoteichoic acid/methylated BSA complexes into rabbits. Precipitin tests showed that the glycerol phosphate backbone is primarily responsible for serological specificity while the polysaccharide part of the molecule plays a minor role. Whole cells of B. bifidum subsp. pennsylvanicum were capable of absorbing antibodies, indicating the presence of lipoteichoic acid (14% of the total content) at or near the bacterial surface. Cross-reactivity with strains of the genera Bifidobacterium and Lactobacillus was tested using absorption of antiserum by whole bacteria and reactivity of phenol extracts. The results indicated that lipoteichoic acid is a common antigen within the genus Bifidobacterium. The cross-reactivity with the lactobacilli tested was very low.