Three-dimensional cellular architecture of the sigmoid filament in Trichomonas vaginalis.

Trichomonas vaginalis is a parasite protozoan that causes human trichomoniasis, a sexually transmitted infection (STI) that affects more than 156 million people worldwide. T. vaginalis contains an uncommon and complex cytoskeleton constituting the mastigont system, formed by several fibers and proteinaceous structures associated with basal bodies. Among these structures is the pelta-axostylar complex made of microtubules and striated filaments such as the costa and the parabasal filaments. In addition, some structures are poorly known and studied, such as the sigmoid filament and the X-filament. Here, we have isolated the Trichomonas vaginalis cytoskeleton and used UHR-SEM (ultra-high resolution scanning electron microscopy), tomography, immunofluorescence, immunolabeling, and backscattered electrons on SEM, negative staining to model the three-dimensional architecture and possible function of the sigmoid.