What are the hair-like projections that help bacilli and spirilla move known as?

The hair-like projections that assist bacilli and spirilla in movement are known as flagella. Flagella are long, whip-like structures that protrude from the surface of certain bacterial cells, enabling them to swim through liquids. They are crucial for motility, allowing bacteria to navigate their environments, find nutrients, and evade harmful conditions.

Cilia, on the other hand, are similar structures but are typically shorter and more numerous, found on some eukaryotic cells that help with movement and the movement of substances along the cell surface. Pseudopodia are extensions of the cytoplasm used by some cells for movement and engulfing food, but they are not hair-like projections. Filopodia are slender, finger-like projections that assist in sensing the environment and movement but do not play a role in the propulsion like flagella do.