Malaria parasites differentially sense environmental elasticity during transmission

Transmission of malaria-causing parasites to and by the mosquito rely on active parasite migration and constitute bottlenecks in the Plasmodium life cycle. Parasite adaption to the biochemically and physically different environments must hence be a key evolutionary driver for transmission efficiency. To probe how subtle but physiologically relevant changes in environmental elasticity impact parasite migration, we introduce 2D and 3D polyacrylamide gels to study ookinetes, the parasite forms emigrating from the mosquito blood meal and sporozoites, the forms transmitted to the vertebrate host. We show that ookinetes adapt their migratory path but not their speed to environmental elasticity and are motile for over 24 hours on soft substrates. In contrast, sporozoites evolved more short-lived rapid gliding motility for rapidly crossing the skin. Strikingly, sporozoites are highly sensitive to substrate elasticity possibly to avoid adhesion on soft endothelial cells on their long way to the liver. Hence the two migratory stages of Plasmodium evolved different strategies to overcome the physical challenges posed by the respective environments and barriers they encounter. Highlights Plasmodium ookinetes can move for over 24 hours on very soft substrates mimicking the blood meal Plasmodium ookinetes change their migration path according to substrate stiffness Plasmodium sporozoites are highly sensitive to subtle changes in substrate elasticity Sporozoite may have evolved to not attach to the soft endothelium to help reach the liver