[The presence of lytic bacteria within cysts of Sarcocystis tenella (Sporozoa, Protozoa) (author's transl)].

In cysts of Sarcocystis tenella parasitic in the oesophage of sheep, bacteria of the Gram-negative type were found to lyse the limiting membranes of the banana-shaped parasites. In cysts of S. tenella the parasites are enclosed within chamber-like hollows of the ground substance. In old cysts, however, only the peripheral hollows are filled with parasites, whereas those of the midzonal region are empty. There is no explanation for this observation reported by several authors. In the present study we found large numbers of small bacteria (2-2.7 by 0.6 -0.8 mum) of the Gram-negative type within the center of the cyst. From this side they were seen to lyse the pellicle of the banana-shaped merozoites. There is no explanation how these bacteria might have penetrated through the muscle tissue into the interior of the cysts, for the parasites at the periphery, the cyst wall and the surrounding host cell were intact. The penetration of the bacteria during preparation can be excluded, too, because the cysts were fixed only seconds after the death of the animals. It might be possible that the bacteria had been present since the beginning of cyst formation.