Gelatin Test, the Carbohydrates (sucrose, lactose, and glucose) Fermentation Test, TSI Agar Test, VP, Litmus Milk Test Results and Methyl Red Test

The results for our VP, gelatin, carbohydrate fermentation, TSIA, and the litmus tests are in! The following images show what we found... 

Above is the result of our VP test. The VP test determines the ability of our bacteria to use butanediol fermentation to ferment glucose. If the test is positive, the presence of oxygen will turn the liquid red upon addition of the VP reagents. As you can tell, our product has turned a reddish color (it was originally yellow) and therefore our test is positive, which means that our bacteria uses butanediol fermentation to ferment glucose.

The fermentation of carbohydrates tests (above) allow us to determine our bacteria's ability to ferment a particular carbohydrate. There are three carbohydrates that we used: sucrose, glucose, and lactose. If our bacteria uses one of these sugars for energy it will produce organic acids as waste products. If this is the case, the phenol red will turn from red to yellow in the presence of acid. As you can see from the picture, the sucrose and glucose tests were positive, meaning they use those sugars. Our bacteria does not use lactose because the medium is still red.

Above is the result of our gelatin hydrolysis test. The gelatin hydrolysis test determines if our bacteria has the enzyme, gelatinase, necessary to digest gelatin. If our bacteria does have gelatinase, it will cause the peptide bonds to cleave in the gelatin, causing the semi-solid to liquefy. If the gelatinous medium is still liquid at 4 degrees Celsius, the bacteria has gelatinase. It's hard to see in the picture, but our gelatin medium has liquefied, and so this test is positive.

The two above images are the result of the TSI (triple sugar iron) agar test. The agar in the TSI test contains lactose, sucrose, and glucose. The agar is originally red. If the bacteria uses any of these sugars, acid is a byproduct, thus causing the agar to turn from red to yellow. As you can see from the image, our slant is red and the butt is yellow. This means that our bacteria only ferments glucose and not lactose and/or sucrose. 

The purple medium in the test tube second to the left is the litmus milk test. The normally-lavender litmus milk medium allows us to differentiate the bacteria's ability to utilize lactose, protien, and litmus in litmus milk. The litmus acts as the pH indicator, turning pink in the presence of acid and blue in alkaline conditions. As you can see from the picture, our medium remained lavender in color. What you can't really see from this picture is that the medium produced a runny curd towards the surface of the medium. This means that our bacteria possesses the enzyme, rennin, to break down the casein. Our bacteria did not turn pink, meaning that it lactose fermentation did not occur.



Methyl Red Test Results: Negative



The above Methel Red test (Mixed Fermentation) shows us if the bacteria has the ability to ferment glucose via mixed-acid fermentation. 5 drops of methyl red are added to the test tube and if it turns red then the test is possitive. If there is no color change are the tube remains yellow, then the test is negative. Our test tube remained yellow so our results are negative.