title: Scanning electron microscopy of Treponema pallidum (Nichols strain) attached to cultured mammalian cells.
abstract: This paper describes the attachment of Treponema pallidum (Nichols strain) to cultured mammalian cells as a visualized by scanning electron microscopy. Treponemes were incubated for 3 hr with cultured cells derived from normal rabbit testes or human skin epithelium, then fixed, processed with critical-point drying, and examined with a Cambridge Mark 2A scanning electron microscope. Large numbers of treponemes became attached to the cultured cells without altering the morphological integrity of the cultured cells. Attachment appeared to involve a very close physical proximity of treponemes to the cultured cells; at the site of attachment, no changes such as swelling or indentation of the cultured cell surface were observed. The addition of ruthenium red to the fixatives produced a treponemal-associated surface precipitate. This material, which is probably mucopolysaccharide and/or phospholipid, may be important in protecting the organisms against host defense mechanisms; in addition, it may be involved in the serological unresponsiveness of freshly prepared suspensions of T. pallidum.
mesh_terms: D000818:Animals; D001431:Bacteriological Techniques; D002478:Cells, Cultured; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008855:Microscopy, Electron, Scanning; D011817:Rabbits; D012430:Ruthenium Red; D014210:Treponema pallidum / Q000648:ultrastructure*
chemical_list: D012430:Ruthenium Red