Lab 15: Catabolism of Carbohydrates -MR-VP AND Citrate Test

MR Test
Growth medium= MR-VP broth
Reagent= methyl red indicator
Positive= red
Negative= yellow
Uninoculated= yellow

Positive MR test =RED

 Negative MR test= Yellow

 Uninoculated Tubes= yellow 

VP Test
growth medium= MR-VP broth
reagent= alpha-naphthol and potassium hydroxide (KOH)
Positive= crimson
Negative= copper
Uninoculated= yellow (see above)

VP test 

 Positive VP= crimson 

 Negative VP= copper 

CItrate test 

-tests for enzyme citrate permease 

Growth medium= Simmon’s citrate agar -contains bromomythmol blue= pH indicator that is green= neutral and blue= basic

Positive Citrate test= blue- bacteria contains enzyme citrate permease 

Negative Citrate test= green- bacteria does NOT contain enzyme citrate permease 

Citrate Test 

Negative Citrate= Green 

Positive Citrate= Blue

note how the one on the right is mostly blue with some green, 

this is still positive bc it is turning blue