Abstract Plasmodium malaria parasites are obligate intracellular protozoans that use a unique form of locomotion, termed gliding motility, to move through host tissues and invade cells. The process is substrate-dependent and powered by an actomyosin motor that drives the posterior translocation of extracellular adhesins which in turn propel the parasite forward. Gliding motility is essential for tissue translocation in the sporozoite and ookinete stages; however, the short-lived erythrocyte-invading merozoite stage has never been observed to undergo gliding movement. Here we show Plasmodium merozoites possess the ability to undergo gliding motility and that this mechanism is likely an important precursor step for successful parasite invasion. We demonstrate that two human infective species, P. falciparum and P. knowlesi , have distinct merozoite motility profiles which may reflect distinct invasion strategies. Additionally, we develop and validate a higher throughput assay to evaluate the effects of genetic and pharmacological perturbations on both the molecular motor and complex signaling cascade that regulates motility in merozoites. The discovery of merozoite motility provides a new model to study the glideosome and may facilitate the pursuit of new targets for malaria treatment. Significance statement Plasmodium malaria parasites use a unique substrate-dependent locomotion termed gliding motility to translocate through tissues and invade cells. Dogma has suggested that the small labile invasive stages that invade erythrocytes, merozoites, use this motility solely to penetrate target erythrocytes. Here we reveal that merozoites use gliding motility for translocation across host cells prior to invasion. This forms an important pre-invasion step that is powered by a conserved actomyosin motor and is regulated by a complex signaling pathway. This work fundamentally changes our understanding of the role of gliding motility and invasion in the blood and will have a significant impact on our understanding of blood stage host-pathogen interactions, parasite biology, and could have implications for vaccine development.

Gliding motility of Plasmodium merozoites