Milk Agar Plate
Differential media
Tests for the presence of the enzyme caseinase
(Hydrolyzes casein (a milk protein) --> amino acid products)
(+) = Clearing
(-) = no clearing -
Starch Agar Plate
Differential media --> amylase
Hydrolyses starch --> simple sugars that can be tra...
MCB 3020 Lab Practical Exam Questions
and Answers
Milk Agar Plate
Differential media
Tests for the presence of the enzyme caseinase
(Hydrolyzes casein (a milk protein) --> amino acid products)
(+) = Clearing
(-) = no clearing -
Starch Agar Plate
Differential media --> amylase
Hydrolyses starch --> simple sugars that can be transported into the cell
Indicator= grams iodine
Iodine + starch = purple color
(+) = No color change/ colorless
(-) = purple around the colony
Lipase Plate
Differential media --> lipase
Hydrolyzes fats --> glycerol and fatty acids
Indicator: spirit blue dye
(+) = blue color
(-) = no color
Oxidase Test
Differential test -->cytochrome c oxidase
(oxidize aromatic amines)
Indicator: dimethyl-p-phenylenediamine hydrochloride DMPD (an aromatic amine)
In the presence of cytochrome c oxidase, the reagent will be oxidized and turn dark blue
to black
(+) = dark blue/black
(-) = colorless
Catalase Test
Differential test --> catalase
Converts hydrogen peroxide (H2O2) --> water and oxygen
Anaerobic (no O2) growth produces hydrogen peroxide which is toxic to the cell
Cell produces catalase to get rid of hydrogen peroxide
Add 3% hydrogen peroxide to the edge of the colony
, Oxygen product will be seen as bubbles coming from the sample
(+) = bubbles
(-) = no bubbles
Litmus Milk
Litmus pH indicator (turns pink at acidic pH)
Acid production
Alkaline production
Curd
Reduction
Proteolysis
Results
(+) Moderate Fermenter= pink
(+) Heavy Fermenter= Curd reaction
(-) Alkaline = blue
Clearing= Casinase +
Labeled Litmus results --
PR Sugar Broth (test for specific sugar fermentation - either glucose, lactose or
mannitol)
Reagent: phenol red and a Durham tube
(+) yellow color = acid
(+) gas + yellow color = acid + gas
(-) Red
(-) Cerise = alkaline -
OF Glucose Media
Tests for Glucose fermentation (Obligate anaerobic fermentation
vs Facultative anaerobic fermentation vs Strict aerobes)
Indicators: Bromthymol blue pH indicator
(closed- adding oil to make anaerobic environment)
Both tubes blue/green = no result
Both tubes yellow = fermentative (F)
Open yellow/closed green = oxidative (O) - Answer-
Vogues Proskauer (VP)
tests for 2,3-butanediol fermenters
Glucose -->AMC-->2,3-butanediol
2,3-butanediol fermenters produce the acetylmethylcarbinol (AMC)/acetoin intermediate
Reagents:
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller lectknancy. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £10.16. You're not tied to anything after your purchase.
