Antigenic Structure Most are motile by peritrichous flagella --H antigens Capsule-K antigen( Vi for Salmonella). Cell envelope(wall) LPS(endotoxin)-O antigen. various outer membrane proteins. Pili-various antigen types, some encoded by plasmidsAntigenic Structure – Most are motile by peritrichous flagella --H antigens. – Capsule – K antigen ( Vi for Salmonella). – Cell envelope (wall) – LPS (endotoxin) – O antigen. – various outer membrane proteins. – Pili - various antigen types, some encoded by plasmids