Diversity of flagellate swimming gaits

Self-propulsion by flagella through a typically fluid medium is a significant selective advantage for microorganisms which possess such capabilities. In species of bacteria, flagella bundle behind a rod shaped cell to propel or push the organism forward. In contrast, the model biflagellate alga C. reinhardtii uses two near-identical flagella to pull itself through the fluid -- executing a breaststroke. In reality neither gait is stereotypical, and instead across flagellate lifeforms there is an unprecedented diversity. Here we explore the implications of this diversity for unicellular algae that have powers of two flagella in terms of their respective swimming gaits, correlating this with a species-specific intracellular architecture. By analogy with limbed locomotion, we show that microalgae likewise rely on flagella to elicit responsive navigation through its surroundings.