A DOUBLE MEMBRANE SURROUNDS THE HYDROGENOSOMES OF THE ANAEROBIC FUNGUS NEOCALLIMASTIX-FRONTALIS

The structure of hydrogenosomes of the anaerobic fungus Neocallimastix frontalis was analyzed using routine preparations for transmission el ectron microscopy, freeze-fracture and immunocytochemistry. They appea red as round or elongated structures, always enveloped by two distinct , but tightly apposed membranes. Images of organelle division were ver y similar to those observed in trichomonad protozoa. These observation s suggest that hydrogenosomes are homologous organelles in unrelated s pecies weakening the hypothesis of a polyphyletic origin and supportin g the evidence that fungal hydrogenosomes are probably derived from an endosymbiont relationship.