Environmental factors determining structural transition in herpetomonas samuelpessoai

Transition from promastigote to paramastigote and opisthomastigote forms of Herpetomonas samuelpessoai in culture is dependent on environmental factors, among which paramount importance is attributed to the oxygen tension, which seems to play a decisive role in determining the choice between the aerobic and the anaerobic modes of respiration. A decrease of the oxygen tension and consequently of the pH, provokes the occurrence of structural transition, particularly in nonaerated cultures. In airgassed media, the changes in PO2 and pH occur at comparatively later stages of the culture and the cell volume does not change appreciably. A direct relationship has been found between the modal cell volume and the extent of structural transition as evaluated by the cell concentrations of the different forms in culture.