This past week in lab Sammy and I
tested the motility of our microbe. Motility is the ability of a microbe to
move on its own. By using a special, soft agar we can see motile bacteria grow
throughout the medium and non-motile bacteria grow only where the inoculating
needle stabbed the agar. We tested a positive control (E. coli) and a negative
control (S. aureus) in the agar to compare to our mystery microbe.
Unfortunately, this specific E. coli we used was actually not motile so both
our controls were negative. Our mystery microbe ended up not growing within the
agar or along the line of inoculation but instead on the surface of the agar.
Since our triple sugar test a few weeks ago showed that our microbe can
tolerate anaerobic growth it is most likely that our microbe is motile and it
“swam” out of the stab and to the surface of the agar.
Bacteria need to possess flagella,
threadlike organelles extending from the cells outer membrane, to be capable of
motility. Different bacteria vary in their number of flagella from one to
numerous. Bacteria can also move using other cellular structures including the
lesser-understood gilding motility, which does not involve flagella. Another
bacterial group called spirochetes move by using axial filaments, which are
similar to flagella.
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| example of flagellum and axial filament structures http://ncse.com/book/export/html/890 http://classes.midlandstech.edu/carterp/courses/bio225/chap04/lecture3.htm |
Some microbes have evolved to be
motile when it is evolutionarily beneficial in their environment. Some microbes
need to be able to flee from a harmful environment and towards a desired
environment. This type of movement is described in our textbook as chemotaxis. Although
it seems evolutionarily beneficial to be motile some bacteria cannot move on
their own. A possible explanation for this is that these bacteria can survive
in harsher environments than motile bacteria and therefor do not need the
energetically costly cellular structures necessary for motility.
So far the dichotomous key has shown us that are microbe fits the following criteria..
1. Gram positive
2. Morphology, Rod Shaped (Bacilli)
3. Non-acid fast organism
4. Catalase activity
5. Endospore positive
2. Morphology, Rod Shaped (Bacilli)
3. Non-acid fast organism
4. Catalase activity
5. Endospore positive
The link for the key we have been using doesn't seem to be working currently but the next step, I believe, was whether our microbe was motile or non motile. According to our soft agar test we can tentatively say our microbe is motile!
6. Motile
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