In merozoites, the malaria cell type that infects our red blood cells, the team observed the typical canonical microtubule shape with 13 protofilaments and was able to visualise other functional structures in detail due to the high resolution of the imaging technique used.
Sporozoites are the malaria cell forms in the saliva of the mosquito, which the mosquito injects into humans when it bites them and which then first migrate to their liver. Ookinetes result from the sexual reproduction of the malaria parasite in the mosquito's intestine: when the gametocytes have become gametes that fuse with each other.
The two parasite cell forms found in mosquitoes, sporozoites and ookinetes, also have the previously assumed microtubule structure with 13 protofilaments. However, in contrast to the merozoites, they again have a special feature: a filling of the cavity within the microtubules known as "interrupted luminal helices" (ILH). The research team suspects that the parasite's specially designed ILH provide stability without compromising flexibility. Balancing flexibility and stability is essential for the parasite's survival at all stages of malaria, and sometimes one is more in demand than the other: flexibility for the cell's dynamics or stability to keep the cell in shape.