How do bacteria move?

Bacteria primarily move using structures called flagella and cilia, which are long, hair-like appendages that can rotate or whip back and forth. Flagella are particularly prominent in many bacterial species, allowing them to swim through liquid environments by rotating like a propeller. Cilia, while more common in certain eukaryotic cells, can also aid in movement by facilitating a coordinated wave-like motion. This mobility mechanism enables bacteria to navigate towards favorable conditions, such as nutrients or away from harmful substances.

The other options do not accurately describe the primary means of bacterial movement. The outer membrane plays a role in the structural integrity and protection of the bacterial cell but does not facilitate movement. While bacteria can sometimes be transported by air or water currents, this passive form of movement is not an active mechanism they employ. Division and replication refer to the process by which bacteria reproduce rather than how they physically move.