The swimming sperm cell reminds us of our aquatic ancestors: the flagellates. While the sperm cell uses its flagellum solely for propulsion, flagellates use their flagellum also for foraging, making them the most important predators on bacteria and picophytoplankton in the ocean. A new review explores the fluid mechanics of predation in a microbial world.
Phagotrophic flagellates forage in a microscopic and nutritionally dilute world: they need to clear huge volumes of water for prey to meet their nutritional requirements, and at the same time the viscosity at this small scale impedes predator prey contact. A naked flagellum, like in a sperm cell, cannot produce sufficient force to produce a feeding current, but the flagellate apparatus in free-living flagellates is adapted in very diverse ways to overcome the impeding effect of viscosity. The number, position, and kinematics of flagella varies between species, and the flagella may be equipped with vanes or hairs, and be beating in depressions on the cell surface, all of which have implications to the fluid dynamics and function of the flagellum. The beating flagellum may also be attracting the flagellates flow sensing predators, and the diverse designs of the flagellar apparatus found among free-living flagellates can be seen as different solutions to this fundamental foraging-predation risk trade-off.
Read the paper here: https://doi.org/10.1146/annurev-marine-020123-102001
Kiørboe T (2023) Predation in a microbial world: mechanisms and trade-offs of flagellate foraging. Ann Rev Mar Sci 16: https://doi.org/10.1146/annurev-marine-020123-102001