Isolation and characterization of a polysaccharide antigen from Propionibacterium acnes released by a glycine-specific chemical protein degradation procedure.

An acid-labile antigenic polysaccharide has been isolated from both cell walls and culture media of Propionibacterium acnes using a new chemical degradation procedure which liberates protein-bound or associated carbohydrate. Lyophilized cells and culture media were treated with a suspension of mercuric oxide in a solution of alkaline mercuric cyanide for several hours at room temperature liberating water-soluble polysaccharide material. The antigenic polysaccharide was freed of reaction products by alcohol extraction and purified by anion exchange chromatography and gel filtration, resulting in three distinct fractions of acidic polysaccharides of apparent molecular weights between 15-150 kDa. Sugar analysis showed the polysaccharides to contain fucose, galactose, glucose, mannose, galactosamine, glucosamine, and 2,3-diamino-2,3-dideoxy-D-glucuronic acid. The three fractions also contained amino acids, predominantly glutamic acid, alanine, and glycine, known to be components of P. acnes cell wall peptidoglycan. All three molecular weight fractions reacted with rabbit antisera raised against whole P. acnes cells, with the highest titer for both cell and media-derived polysaccharide material consistently in the high molecular weight fraction. This procedure was also capable of releasing antigenic polysaccharide from tissues of rats administered P. acnes cells or radiolabeled cell wall fragments.