Labs 4,6,7 Flashcards
What is in starch agar?
Starch, if you flood with I a clear zone will appear (If starch has been hydrolyzed)
Whats in milk agar?
Production of an enzyme capable of degrading casein=clear zone
What is phenol red and what is it used for?
pH indicator, turns yellow when sugar is fermented because acid is produced
What is in the peptide iron agar?
Contains cysteine. Some organisms can degrade (with cysteine desulfurase) it to yield H2S, which reacts with ferric ammonium citrate=black precipitate
What is the black precipitate formed in the peptone iron medium?
Ferrous sulfide
What is in nitrate broth?
No3- (nitrate) as only source of N
How are nitrate broths used to differentiate organisms?
Some organisms can reduce nitrate to NO2- or NO or N2O or N2. Nitrite reagent will change colour depending on which.
Is nitrite reagent is added into nitrate broth and it turns red, what was in the broth?
Nitrate reducer if no Zn added
No nitrate reduced if Zn added
What does it mean when theres no change in colour after Zn is added to the nitrate broth?
Organism was a full denitryifier.
What are the IMViC tests?
Series of 4 tests:
- Indole test
- Methyl Red test
- Acetyl methyl test
- Citrate test
What are the IMViC tests used for?
Used to differentiate members of gram negative intestinal bacilli.
What does the indole test detect?
Production of indole from tryptophan in tryptone broth
What does the methyl red test detect?
Indication of extent of acid production from glucose in Mr-VP medium.
What does the cirate test detect?
Determines whether organism can use citrate as sole carbon source.
How do you test whether an organism has created acetyl methyl carbinol?
Add dropper full of VpI and VPII to culture in MR-VP broth. Positive =pink
