Ex. 18: IMViC Reactions

1. Indole production test Methyl red test Voges-Proskauer test Citrate utilization test. Ex. 18: IMViC Reactions Objectives ??

2. Day 1

3. Day 2

4. Indole Test Checks for Tryptophanase • Medium: 1% Tryptone broth Test for indole with Kovac’s reagent • DMABA in Kovac’s reagent combines with indole and forms red band at the top of the medium

5. Enterobacter aerogenes E. coli

6. Methyl Red and Voges-Proskauer Tests • Physiologically related tests, use same medium (MRVP broth), NB with glucose • MR test checks for large amounts of acid endproducts from glucose fermentation • Do not confuse methyl red indicator with phenol red indicator!!! • VP test checks for production of acetoin, a neutral fermentation end product

8. MRVP after incubation and before adding test reagents

9. MR test After addition of 3 -4 drops of methyl red indicator Explain the meaning of this outcome

10. VP Test After addition of 15 drops of VP reagent A, and 5 drops of VP reagent B E. a. E. c. Explain the meaning of this outcome

11. Citrate Utilization Test • Checks if organism has citrate permease • Simmons citrate agar also contains ammonium phosphate as sole N-source and bromothymol blue as indicator. • If bacterium is able to use citrate it will also convert ammonium phosphate to NH3 and NH4OH

13. the end

14. Could an organism be both MR and VP positive? Explain. The End