ELECTRON MICROSCOPY OF <i>TREPONEMA CUNICULI</i>

Abstract

Treponema cuniculi was studied in the electron microscope by means of negative staining and ultrathin sectioning techniques. The sectioned organisms were studied in situ in biopsies from lesions of infected skin. Cells of T. cuniculi were found to be regular helices 8–15 μm long and 0.15 μm wide. The ends of the cells were pointed and three flagella were inserted in a row subterminally at each end. The flagella wound around the organisms and overlapped in the middle of the treponemes. The fine structure of isolated flagella was similar to that of flagella obtained from other treponemes. Treatment of T. cuniculi with Myxobacter AL‐1 protease 1 revealed bundles of intracytoplasmic microtubules. The diameter of each tubule was about 7 nm. In the ultrathin sections of infected tissue T. cuniculi was observed in intercellular spaces in the stratum spinosum and the stratum basale layers of the epidermis. No treponemes were observed in the connective tissue of the dermis. Sections of the microorganisms show the same structural pattern as previously described for T. pallidum Nichols. The organisms are surrounded by two tripple‐layered membranes with the flagella situated in between. The ultrastructure of the pathogenic treponemes, T. cuniculi, T. pallidum and T. pertenue is compared.