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
What is Kovac’s agent and what is is used for?
Used in indole test
What is a positive test in the indole test?
Red ring in alcohol layer
What is a positive test in the methyl red test?
Pink
What is a positive test in the Voges Proskauer test?
Pink
What is a positive test in the Citrate simmons agar?
Bright blue
What is S. aureus?
Gram +
Produces acid from mannitol
Resistant to NaCl
What is S. epidermis?
Gram +
Resistant to NaCl
What is E. coli?
Gram -
Produces acid from lactose
Sensitive to NaCl
What is P. aeruginosa?
Gram -
Produces no acid from lactose
Sensitive to NaCl
What is the necessary pore size to sterilize with filtration?
0.45 microm
How does moist heal kill bacteria?
Coagulating proteins, renders enzymes inactive
True or false. Moist heat kills faster than dry heat.
True. Vegetative cells contain more H2O.
How does UV light damage cells?
Induces dimerization of adjacent thymine residues. Causes errors in DNA replication
How can the bactericidal effect of UV be reduced?
immediate exposure to certain wavelengths of visible light. (Photoreactivation)
What is photoreactivation?
Photolyases are DNA repair enzymes that repair damage caused by exposure to ultraviolet light. These enzymes require visible light both for their own activation and for the actual DNA repair. The DNA repair mechanism involving photolyases is called photoreactivation.
How does dry heat kill bacteria?
Oxidizing various components of cell
