Methyl Red Voges-Proskauer Test Lab Essay

1335 Words Apr 18th, 2015 6 Pages
Methyl Red Voges-Proskauer Test Lab

Tetia Richardson
Microbiology DL3: Instructor Newton
3/29/2015

PURPOSE
This experiment is designed to become familiar with and perform the MR-VP biochemical test, learn variations in how different organisms metabolize glucose, and to become familiar with and perform the catalase biochemical test.

Materials Used
10% bleach solution
Hydrogen peroxide
Paper towels
Saved E. coli culture
Stock culture: S. epidermidis
Gloves
Candle used for a flame source
Test Tube
Test Tube rack
Pipet
Slide-Box-MBK with blank slides
2 Broth, MR-VP - 5 mL
1 Barritt’s A Reagent - 3 mL in Pipet
1 Barritt’s B Reagent - 3 mL in Pipet
Methyl Red Reagent, 0.1% - 1 mL in Pipet
1 Inoculation Loop,
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The tubes were gently shook for 30 seconds. The broth was exposed to oxygen for a color reaction to occur.
The tubes were left to stand for 30 minutes before interpretation began.

Exercise 2
Procedural Steps
The work area was disinfected.
Two microscope slides were labeled one E. coli and S. epidermidis.
A plastic inoculation loop was used to transfer a sample of each organism to the corresponding slide.
A drop of hydrogen peroxide was added to the smear. The plastic loop was used for mixing.
The results were interpreted: a positive test was the evolution of oxygen gas evidenced by bubbling or foaming; a negative result was the evidence of no bubbles or only a few scattered bubbles.

DATA/OBSERVATIONS

Methyl Red Test: Pre-reagent [pic]

Figure 1 shows the test tubes of the pre-reagent for the Methyl Red Test. Two tubes of MRVP contained E. coli (labeled with a yellow E tag) and the other containing the S. epidermidis after incubation. Only two of these tubes located in the front of the test tube rack were used the Methyl Red Test.

Methyl Red Test: Post-reagent [pic]

Figure 2 shows two tubes of MRVP containing E. coli and S. epidermidis after incubation and after adding the reagent (Methyl Red Test). Using the pipet, eight drops of Methyl Red reagent were added to each of the tubes. Both the E. coli and S. epidermidis turned red indicating the

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