"F." Is he Anaerobic and what does he eat?

Lab today revealed much about the treacherous life of "F" and how likely he is to survive!  In which conditions does "F" thrive? Let's find out!

The Oxygen Requirements of "F"

Recall, from the last blog we placed our bacteria in a GasPak in order to test if they could thrive in an environment without Oxygen. The chemical bags inside the GasPak eliminated the Oxygen. Also recall, that we made a Thioglycollate Broth culture of our unknown bacteria.

Results:

 The bacteria that was stored inside the GasPak is shown above. Note, that there is some growth on the plate, thus our bacteria is able to grow in a deoxygenated environment. Remember from previous labs that we ALWAYS grew our bacteria in an oxygenated environment as well. Therefore, because it grows in both conditions our bacteria is considered "Facultative".

To further prove that "F" is facultative, we analyzed the results of a Thioglycollate Broth. This broth also depicted large amounts of our bacteria growing throughout it. Bacteria was present in the reddish area depicting Oxygen, towards the top of the broth. Also, it was noticed reaching throughout the yellow broth towards the bottom of the tube, depicting its ability to grow without Oxygen. Growth was equal in both areas.

Starch, Casein, and Triglyceride Testing: 


Next, we proceeded to do tests to see what kind of nutrients our bacteria feasts on! To do this we acquired three agar plates: one containing starch, one containing a milk protein (known as Casein), and the other containing a lipid (known as a Triglyceride). Using the aseptic technique we inoculated the surfaces of each of these plates and placed them in the 37 degree Celsius incubator for 24 hours.

In the above photo the nutrient plates are as follows: Starch, Triglyceride, Casein.

Later... with the results...

The nutrient plates are as follows: Casein, Starch, Triglyceride.

Starch: 


In order to check to see where Starch was present in the agar, we covered the plate in Gram's Iodine for 30 seconds - 1 minute, waiting for the purple color to appear.

Notice the top half of the plate, this is where good old "F" is found (the bottom is a sample from a different set of bacteria for comparison in our lab). The Starch plate contains Amylopectin and Amylose. If there were a halo around our bacteria streaks (located on the top) then our bacteria would contain the enzyme Amylase, and thus be able to digest Starch. However, since our bacteria lacked this halo and had a blue black precipitate under the streak, it was unable to feed on the Starch present.

Casein: 

This Casein plate revealed no mysteries, other than the simple fact that neither of the bacteria feeds on the nutrient Casein. This is revealed through the opaque white surface that covers the entire plate, even after incubation. If Casein eating bacteria were present there would be a halo around the streak of bacteria, thus our bacteria does not produce the enzyme Casein Protease.

Triglyceride: 

The photo at the top depicts both of the bacterias -- ours is to the right with the blue color (also pictured separately above). The dark blue precipitate appearing in our sample with the bacteria proves that  the triglycerides in the agar underwent partial hydrolysis. This means that our bacteria was positive for the enzyme Lipase, and thus gets its nutrients from fat. The other sample pictured tested negative for the enzyme, take time to note the aesthetic difference.

Join us next time to discover more mysteries about "F". Now, we are going to go enjoy our lunches, though I can assure you it won't be the same lunch as "F" is eating right about now.