Final answer:
Some bacteria move using flagella, which are like tiny tails propelled by biological motors. This allows movement speeds up to 50 µm/s, significantly larger than their non-assisted terminal velocity. Observations in stab cultures can provide evidence for bacterial motility.
Step-by-step explanation:
It's true that some bacteria are propelled by biological motors. This movement is facilitated through cellular structures known as flagella. Flagella operate like small engines that rotate to move the bacterium forward. Because bacteria are so small, with sizes approximately 1 µm, the total distance they can move is quite significant relative to their size, even though their actual displacement may remain small.
Bacterial flagella are made up largely of the protein flagellin, which is a key component granting these microorganisms the ability to be motile. This movement, often called chemotaxis, is a response to environmental chemicals where bacteria can move toward or away from nutrients or toxic substances. Observations in a stab culture can indicate whether bacteria are motile, based on their ability to diffuse away from the line of inoculation.
Terminal velocity concepts explain that without the aid of mechanisms like flagella, small organisms like bacteria can only travel at constant speeds due to their minute size. However, bacteria equipped with flagella can achieve speeds up to 50 µm/s, which is significantly faster than their terminal velocity of around 2 µm/s. This remarkable motility enhancement is due to the biological motors powering the flagella. A stab culture can be a clear indication of activity that suggests motility in bacteria.