Urea

       The purpose of this test was to determine if our bacteria could hydrolyze urea, and break it down into carbon dioxide and ammonia. 

First we inoculated a broth tube of urea with our unknown bacteria. We then incubated the sample for 48 hours before we read the results. Our results showed that the broth turned a yellow color which indicates that our bacteria is negative for hydrolyzing urea. However, if the broth turned a red/ pink color, the test would be positive. The red color is related to the ph change. Our bacterial broth had not achieved a pH change. 

Nitrate experiment

The nitrate test was performed in order to indicate if our bacteria was able to reduce nitrate ions to nitrite ions or nitrogen gasses. Nitrate reduction is usually for energy production during anaerobic conditions. To determine whether the bacteria used nitrate reduction can test the presence of nitrite ions. To detect nitrite ions, sulfanilic acid and dimethyl alpha naphthylamine are added to bacteria inoculated in nitrate broth. If the broth turns pink, nitrite is present, and the results for nitrate reduction are positive. However, having no color change does not determine a negative result. Instead, Zinc has to be added to determine if the nitrate ions were reduced to molecular nitrogen. If the color does not change after the addition of Zinc, the results are considered to be negative.  

First we inoculated a nitrate broth tube with our bacteria and let it incubate for 48 hours. Next, we added 5 drops of the two reagents listed above and proceeded to mix the contents. Right away, our broth turned red. Our bacteria is positive for nitrate reduction. We did not have to add zinc to the broth because the two reagents gave us instant results. The broth contained nitrite ions!

Citrate examination

The citrate test was performed in order to determine if citrate could act as our bacteria’s energy source. Bacteria which use citrate have membrane transporters called Citrate Permease. Citrate Permease convert the citrate to pyruvate and carbon dioxide. For this test we used Simmons citrate agar slant tube. The slant has a green agar that will turn blue if the bacteria utilizes citrate. We inoculated the slant and incubated it for 48 hours. The results turned out to be negative for the utilization of citrate as indicated by the green color of our slant agar.

Indole

       The indole test’s purpose was to determine the ability of our bacteria to split amino acids( tryptophan) into indole and pyruvic acid. The simple procedure had us first inoculate the tryptone broth with our bacteria and incubate it for 48 hours at 35 degrees C. After the incubation, we had to add 5 drops of Kovac’s reagent to broth. Right when we added the Kovac solution to the indole tube the top layer turned a redish, pink color which meant that our bacteria was positive for the presence of indole. Our bacteria successfully split the amino acid, tryptophan into indole and pyruvic acid. 

Antibiotic plate

For this experiment we wanted to test which antimicrobial agent our bacteria would be susceptible to.  We placed small samples of the antimicrobial agents onto a streaked plate of our bacteria. The next lab day we recorded the clear diameter of dead bacteria surrounding each microbial agent.

Diameter surrounding each


1.Penicillin : 1cm
2.Vancomycin: 1.2 cm
3.Novobiocin: 0 cm
4.Tetracyclic: 2 cm
5.Erythro: 1.9 cm
6.Chloramphenicol: 3 cm
7.Neomycin: 2 cm

By measuring the diameters we found that our bacteria was susceptible to Vancomycinb, Tetracyclic, Chloramphenicol, and Neomycin

Eosin methylene blue agar

       The purpose of this procedure was to isolate a gram-negative enteric bacilli. The type of agar used is called an Eosin Methylene Blue medium. The medium contains the dyes eosin, methylene, and the sugars lactose, and sucrose. The medium inhibits gram-positive bacteria growth, and only gram-negative bacteria. The primary use of this agar is to identify Enteric bacilli. 

We began by inoculating the agar with our bacteria using aseptic technique. We then let the medium incubate for 48 hours. Our results were very specific and exciting!!! The color of our bacterial streak turned to a dark purple, green metallic sheen. Our bacteria is able to ferment lactose and/or sucrose and produce acids. Our lab book stated that our results indicated that our bacteria was Escherichia coli! Exciting! This test helped us in our bacteria identification!!

MacConkey Agar

For this procedure we used a MacConkey agar in order to differentiate between gram-negative enteric bacteria and their ability to grow on the agar and ferment lactose. First we used aspetic technique to inoculate the agar plate with our bacteria. Next, we incubated the sample for 48 hours at 35 degree celsius. We examined the plate the next day and found a negative result. We concluded that because there was not a broad change of color on the agar, the bacteria was a non-lactose fermenter.