Treponema

Trep.o.ne'ma. Gr. v.trepôto turn; Gr. neut. n.nemaa thread; N.L. neut. n.treponemaa turning thread.Spirochaetes / Spirochaetia / Spirochaetales / Spirochaetaceae / TreponemaHost‐associated, helical cells 0.1–0.7 μm in diameter and 1–20 μm in length. Cells have tight regular or irregular spirals and one or moreperiplasmic flagella(axial fibrils or axial filaments) inserted at each end of the protoplasmic cylinder.Cytoplasmic filamentsare seen in the protoplasmic cylinder just under the cytoplasmic membrane and running parallel with the periplasmic flagella. Under unfavorable cultural or environmental conditions, spherical cells are formed. These can also be seen in old cultures. Gram‐stain‐negative. Cells stain well with silver impregnation methods. Most species stain poorly, if at all, with Gram or Giemsa stain. Best observed with darkfield or phase‐contrast microscopy.Motile. Cells have rotational movement in liquid media, and translational motion in media with high viscosity[e.g.,those containing 1% (w/v) methyl cellulose]. In a semisolid or solid medium, cells exhibit a serpentine type movement, sometimes referred to as creeping motility.Strictly anaerobic or microaerophilic. Frank pathogens (Treponema pallidumsubspecies,Treponema carateum, and the rabbit pathogenTreponema paraluiscuniculi) represent a closely related subset within this genus and are considered microaerophiles. Limited multiplication ofTreponema pallidumsubsp.pallidumstrains has been obtained in a tissue culture system, but none of the pathogenicTreponemahave been cultivated continuously in artificial media or in tissue culture.Chemo‐organotrophs, using a variety ofcarbohydrates or amino acids for carbon and energy sources. Cultivated anaerobic species are catalase‐ and oxidase‐negative. Some require long‐chain fatty acids found in serum for growth, while other cultivated species require short‐chain volatile fatty acids for growth.Host‐associated. PathogenicTreponema pallidumsubspecies cause skin lesions, andTreponema pallidum(particularly subspeciespallidum) can cause systemic infections that, if untreated, can last for years to decades. Other species are found in the oral cavity, intestinal tract, and genital areas of humans or other mammals, and in the gut contents of wood‐feeding insects.DNA G+C content(mol%): 37–54.Type species:Treponema pallidumsubsp. pallidum (Schaudinn and Hoffman 1905) Schaudinn 1905, 1728AL.