Rabbit Anti-T. pallidum Polyclonal antibody for IHC, IF. Treponema pallidum is a species of spirochaete bacterium with subspecies that cause treponemal diseases such as syphilis, bejel, pinta and yaws. The treponemes have a cytoplasmic and outer membrane. They are not seen on a Gram stained smear because the organism is too thin to be observed under a light microscope. The recent sequencing of the genomes of several spirochetes permits a thorough analysis of the similarities and differences within this bacterial phylum. Treponema pallidum subsp. pallidum has one of the smallest bacterial genomes at 1.14 million base pairs (Mb), and has limited metabolic capabilities, reflecting its adaptation through genome reduction to the rich environment of mammalian tissue. The shape of Treponema pallidum is flat and wavy, unlike the other spirochetes, which are helical.