Motility Test

 

What is the purpose of the test? 

 

Some bacteria have the ability to propel themselves through liquids by means of flagella (flagellum = singular). These long fibers of protein are found on many bacteria, including most supported by this simulation. However, not all bacteria are able to "swim", even if they have flagella. The purpose of this test is to see if the microbe can "swim" by means of flagella.

 

 

How is motility determined? 

 

Motility can be detected in a couple of ways. For this simulation, motility will be monitored by means of microscopically observing the bacteria in a wet mount.

 

 

What medium is used?  

 

No special media are required for this test, although use of broth cultures is preferred. Only fresh cultures (18-24 hr) of the bacterium grown on a nonselective medium should be used for preparing the wet mount to be observed.

 

 

How is the test performed?  

 

Fresh growth (not over 24 h old) should be used for preparing the wet mount. The growth is transferred to a drop of water or saline on a microscope slide, mixed, and a cover slip is added. For VirtualUnknown™ Microbiology, the work has been done for you, and a video displays the scene under the microscope.

 

Motility is interpreted using high dry magnification to locate the bacteria within the drop of water. If they swim randomly and "against the current" of water streaming across the slide surface, they are positive for motility. If they seem to be buffeted around, all moving the same direction and at the same speed, there is no motility. Instead, this type of movement is the result of the bacteria being knocked about by water molecules, called Brownian movement.

 

 

What reagents are added?

 

None.

 

 

To view the motility test in VirtualUnknown™ Microbiology, complete the following steps:

 

1. Select View -> Motility Video from the Main Menu.

 

2. Press the Play button to watch the video. A short video clip showing microscopic observation of a wet mount of the unknown organism will play.

 

3. Observe the results. If the bacteria are motile, movement of individual bacteria will be random but purposeful and at different speeds. If the bacteria are nonmotile, all cells will "quiver" and/or move the same direction at the same speed as the wet mount shifts under the cover slip.

 

4. Record the result by pressing the Record Result button on the Motility Video Screen. and selecting the appropriate result.