Cytokinesis arrest and nuclear fission in low density populations of trichomonad protozoan

Abstract Cell growth of anaerobic protozoan Tritrichomonas foetus was analyzed. This protozoan usually proliferates in extremely high density, but protozoan parasites were dispersed uniformly in F-bouillon medium and cell division stopped temporarily. However, nuclear fission continued and giant polynucleated cells formed. Later, cell division resumed and cells returned to normal form. In conditioned medium, cytokinesis of the dispersed parasites did not stop. Results indicated that T. foetus cells secreted an extra-cellular factor that influenced cytokinesis.