Bacterial Motility

Bacteria have multiple ways of moving around their environment. Some bacteria have a single tail-like structure, called flagellum, or a small cluster of flagella, that can rotate in a coordinated fashion, like a propeller. When the cluster of flagella rotate in an anticlockwise direction, it causes the bacteria to tumble randomly, instead of moving in a single direction. The structure of the flagellum itself is quite advanced and consists of multiple subunits.

Many prokaryotes have short, fine, hairlike appendages, that are thinner than flagella. These are called fimbriae. Fimbriae are important for attachment to surfaces. Another structure protruding from the bacteria is the pilus. Pili are often larger than fimbriae and can pull the bacteria forward along a surface like a grabbing hook. Pili typically facilitate twitching motility characterized by short intermittent jerky motions. Certain specialized pili are involved in the transfer of genetic material from one bacteria to another, a process called conjugation.

Bacteria don’t move aimlessly but because they don’t have a brain center, they rely on chemical cues from its environment to guide movement, a involuntary process called chemotaxis. Bacteria can be attracted to different nutrients or environmental cues. They can also get repelled by harmful substances and bacterial waste products.

Some bacteria also seek out each other. These bacteria cluster together and create a coordinated swirling movement pattern together. They can cluster in a biofilm providing additional characteristics that the bacteria can’t obtain independently.