Methyl Red and Voges-Proskauer Tests
Micro Lab Exam 2
Terms in this set (14)
What kind of medium is Methyl Red and Voges-Proskauer (MR-VP) Broth?
Is a combination medium used for both Methyl Red (MR) and Voges_Proskauer (VP) tests.
What are the main ingredients in MR-VP broth?
-Methyl Red (for MP test)
-VP Reagents (for VP test)
What do the Peptone and Glucose do in the MR-VP broth?
The Peptone provides Protein and the Glucose provides a Fermentable Carbohydrate.
What does the Potassium Phosphate do in the MR-VP broth?
It resists pH changes in the medium, acting as a Buffer.
What does the Methyl Red do in the MR-VP broth?
It is a Dye that indicates pH after Mixed Acid Fermentation, being added after incubation.
What do the VP Reagents do in the MR-VP broth?
They Oxidize the Acetoin and Diacetyl which were presumably products of Glucose Fermentation. The Oxidized Acetoin and Diacetyl reacts with Guanidine Nuclei from Peptone to produce an indication color.
What doe the different Colors of the MR test tell you?
-Red = pH 4.4 (positive indicator)
-Yellow = pH 6.2 (negative indicator)
- Various Shades of Orange = pH between 4.4 and 6.2
If you get a Red (positive result) from the MR test, what does that tell you about the Organisms you are studying?
It tells you that the acids produced by these organisms are stable, whereas other organisms produce acids that are unstable and are converted to neutral products.
What does Color indicate about the VP test?
-Red (positive indicator)
-No Color or Copper Color (negative indicator)
If you get a Red (positive result) from the VP test, what does that tell you?
Organisms that can Ferment Glucose, but quickly Convert their Acid Products to Acetoin and 2,3-Butanediol are present.
What is the MR and VP test used typically used for?
They are components of the IMViC battery of tests used to distinguish between members of the family Enterobacteriaceae and differentiate them from other Gram-Nagative Rods.
What VP reagents did we use?
What organisms were did we use in the MR-VP test?
What steps were performed in the MR-VP test?
1. Inoculate 1 tube containing MR-VP broth with pure culture
2. Incubate for 48 hours
3. Transfer 1.0 mL of broth to 2 Nonsterile test tubes
4. Add 3 Drops of Methyl Red to one and read results immediately.
5. Add 15 drops of Naptha Alpha and mix; Add 5 Drops of KOH and mix well to Oxygenate.
6. Read results at 10 Minute intervals for 60 minutes.