Carbohydrates fermentation, TSI, MR-VP, Gelatin

Fermentation of Carbs

We performed this procedure to detect if our bacteria could ferment lactose, sucrose, or glucose by indicating the acid/gas production. The procedure began by inoculating our bacteria into three different phenol red-sugar broth, each with Durham tubes to collect the gases. Each tube was labeled with a different sugar; lactose, glucose, or sucrose. 

After letting the tubes sit for 48 hours, we recorded our results...

Lactose: pinkish/yellow, gas bubble present= acid/gas production

Sucrose: Orange/red, little gas bubble=acid/gas production

Glucose: Light Yellow, big gas bubble=acid gas production

TSI

During this lab we inoculated many tubes with our unknown bacteria. First we inoculated a triple sugar ion(TSI) slant which will indicate if the bacteria has the ability to ferment glucose, lactose, and sucrose. The triple sugar agar contains all 3 sugars and if our bacteria end up fermenting any of them, there will be a drop in pH. All we did was streak the slant in a zig zag fashion and allowed the bacteria to grow in an incubator for 24 hours. 

Unfortunately pictures are not available with the results but I will do my best to describe what happened. Our slant turned yellow. It had a yellow slant and yellow butt which means that glucose, lactose or sucrose fermented. We also noticed that there was a big gas bubble near the butt which means that it was a bacteria producing acid and gas. 

MR-VP 

The MR-VP test was to determine if the bacteria had the ability to ferment glucose via butanediol fermentation. We inoculated our bacteria into the MR-VP broth tube and incubated it for 48 hours. After 48 hours we added 1 ml of our MR-VP mixture to a smaller tube. We then added 5% alpha-napthol and 40% KOH. We proceeded to shake the smaller tube and read our results. There was no indication of color change at all because it remained yellow. If the color turned to red it would have been a positive result for the usage of butanediol fermentation. 

Next we added 10 drops of methyl red to the original tube and got a positive result for our bacteria’s ability to ferment glucose via mixed acid fermentation. The top of the broth changed to a redish color. 

Gelatin 

The gelatin test was preformed to determine the bacteria’s ability to digest gelatin. We inoculated our bacteria into the gelatin and incubated it for 48 hours. The next day we checked the liquifaction by tilting the tube. The medium remained as a liquid indicating that our bacteria is negative for hydrolyzing gelatin.