It is possible to watch living bacteria swim around using the phase microscope. This is a semisolid medium that will hold non-motile bacteria in place, but motile microbes can swim through it. The presence of turbidity throughout the tube is a positive test for the presence of motility. Typically microbes that live in aqueous environments will continually move around looking for nutrients. Sometimes this movement is random, but in other cases it is directed toward or away from something.
Bacteria are capable of a tactic response to various stimuli.
This is cool. One example is Aquaspirillum magnetotacticum , which has magnetosomes. The microbe uses this to determine which way is up and that helps it to find nutrients or adjust its depth in an aquatic environment. In these cases they are used for navigation on long migrations. Chemotaxis Chemotaxis is accomplished by sensing the environment and adjusting the rotation of the flagella in response to stimuli.