Treponema pallidum is a species of spirochaete bacterium with subspecies that cause treponemal diseases such as syphilis, bejel, pinta and yaws. It is not seen on a Gram stained smear because the organism is too thin. Alternative Names: p Treponema pallidum-15 protein, p Treponema pallidum-15, p15 Treponema Pallidum Antigen, p Treponema pallidum 15 protein, p15 Treponema pallidum, p Treponema pallidum 15