Description and Significance
Parabasalids (phylum Parabasalia) are anaerobic flagellated protists which contain at least one parabasal apparatus consisting of a parabasal body (Golgi complex) and a parabasal filament. Parabasalids can be distinguished by the presence of the microtubular axostyle-pelta complex, composed of a sheet of cross-linked microtubules that are the longitudinal axis of the cell. Trichomonas vaginalis is a parabasalid that causes a sexually transmitted disease in humans. Other parabasalid species live in the intestines of some cockroaches and termites, enabling them to break down the cellulose in the dead plant material they eat. These symbiotic parabasalids in turn have symbiotic bacteria that aid in locomotion and cellulose breakdown. The relationships of the parabasalids with their hosts and with other symbionts are complex and in most cases not well understood.