ACTIN CYTOSKELETON DEMONSTRATION IN TRICHOMONAS-VAGINALIS AND IN OTHER TRICHOMONADS

The flagellate form of Trichomonas vaginalis (T nu) transforms to amoe boid cells upon adherence to coverslips. They grow and their nuclei di vide without undergoing cytokinesis, yielding giant cells and a monola yer of T nu F-actin was demonstrated in Trichomonas vaginalis by fluor escence microscopy using phalloidin and an anti-actin mAb which labell ed the cytoplasm of both the flagellate and amoeboid forms. Comparativ e electrophoresis and immunoblotting established that the actin band h as the same 42 kDa as muscle actin, but 2-D electrophoresis resolved t he actin band into four spots; the two major spots observed were super imposable with major muscle actin isoforms. Electron microscopy demons trated an ectoplasmic microfibrillar layer along the adhesion zone of amoeboid T nu adhering to coverslips. Immunogold staining, using anti- actin monoclonal antibodies demonstrated that this layer was mainly co mposed of actin microfilaments. A comparative immunoblotting study com prising seven trichomonad species showed that all trichomonads studied expressed actin. The mAb Sigma A-4700 specific for an epitope on the actin C-terminal sequence labelled only actin of Trichomonas vaginalis , Tetratrichomonas gallinarum, Trichomitus batrachorum and Hypotrichom onas acosta, but not the actin of Tritrichomonas foetus, Tritrichomona s augusta and Monocercomonas sp. This discrimination between a 'tricho monas branch' and a 'tritrichomonas branch' is congruent with inferred sequence phylogeny from SSu rRNA and with classical phylogeny of tric homonads.