The Case of the Mystery Bacteria: Part IV

It has been 23.25 hours and I am exited to analyse the results.  Here is a picture from when I opened the incubator, looks promising!

We will take the results one by one:

1) Glucose Fermentation

Tube on the left

• Observations: color changed to yellow; a small bubble roughly 3.0 mm in diameter and 1.5mm in height was visible in durham tube.
• Analysis:  The yellow color indicates a positive acid test; the bubble is quite small 

2) MSA (Mannitol Salt Agar)

• Observations:  Colonies produced at a rate beyond that of a TSA plate.  In all areas of colony expansion medium change from red to yellow in color indicating sugar metabolism.
• Analysis:  Bacteria is positive for the ability to ferment mannitol (a sugar) and grows well in a high salt concentration medium

3) Motility

• Observations: no color change
• Analysis:  The bacteria does not have flagella. 

To recap,  the bacteria tested positive in the Glucose Fermentation and MSA test and negative in the motility test.

If we take a look at the dichotomous key we have good reason to believe that our bacteria is.....

Stapylococcus aureus

After checking with advisor on the project I discovered that this deduction was correct.  The mystery is no longer.  Thanks for coming along with me on this journey through my first experiments in biology.  

I will have more for you soon.