BIOL 2120
HCC-Stafford Campus
J.L. Marshall, Ph.D.
Laboratory 9- Bacterial Flagella and Motility Testing*
*Laboratory notes are to be used as a study guide only and do not represent the comprehensive information you will need to know
for the exams.
Many species of bacteria move by using flagella (flagellum, singular). Bacteria respond to stimuli in their
environment such as chemicals and light. When bacteria move in response to chemicals it’s called chemotaxis,
and when they move in response to light it’s called phototaxis. Taxis means movement. But, not all bacteria
are motile, due to the lack of any flagella.
There are a few ways to test motility: staining method, live preparation, and motility test medium. We will use
motility test medium.
To test motility using motility test medium, you will use an inoculating needle. The bacteria will be inoculated
into this medium that contains a dye, TTC, that is visible when the bacteria grow and/or move through the
medium. If you see growth at the line of inoculation and away from the line of inoculation, then the bacterium
is motile. If you only see growth at the line of inoculation then the bacterium is not motile. + motile ~ flagella;
- motile ~ no flagella.
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