BIOL 206 TAMU LAB PrAcTIcAL (ExAM 2) ExAM WITH cOrrEcT
AcTUAL QUESTIONS AND cOrrEcTLY WELL DEFINED ANSWErS LATEST
ALrEADY GrADED A+
Oxidase Test - ANSWEr-*Positive Oxidase Test:*
-Turns blue within 20-30 seconds
*Negative Oxidase Test*
-No color change within thirty seconds
*Reagent used:*
-Oxidase
What is the purpose of the oxidase test? - ANSWEr--The tests is used to identify bacteria containing the
respiratory enzyme cytochrome c oxidase. Differentiate between enterobacteriaceae and
pseudomonadaceae
How is the oxidase test performed? - ANSWEr-1. Transfer bacterium to the paper
2. Add drops of complex A & B to bacterium
3. Observe for color change within 30 seconds
,Why should you read the results of the oxidase test within 30 seconds? - ANSWEr--The reagents of this
test are unstable, therefore they may oxidize independently due to exposure to air.
Catalase Test - ANSWEr-*Positive Catalase*
-Visible Bubble production
*Negative Catalase Test*
-No Bubbles
*Reagent Used:*
-Hydrogen Peroxide
Why is the Catalase Test Used? - ANSWEr--This test is used to identify organisms that produce the
enzyme catalase, and its ability to break down hydrogen peroxide. Differentiate between micrococci and
streptococci
How is the catalase test performed? - ANSWEr-1. Transfer a large amount of growth to slide
2. Place one to two drops of hydrogen peroxide on bacteria
3. Observe for bubbles
, MacConkey Test - ANSWEr-*Poor Growth or No growth:*
-Organism is inhibited by CV and/or bile, therefore is Gram-positive
*Good Growth:*
-Organism is not inhibited by CV and/or bile, therefore Gram-Negative
*Pink to red growth with or without bile precipitate:*
-Organism produces acid from lactose fermentation therefore is a probable coliform
*Growth is "colorless" (not red or pink):*
-Organism does not ferment lactose, therefore is a noncoliform
What does the bacteria look like on a MacConkey Media? - ANSWEr-*Negative Growth:*
-Streak lines visible, but no colonies (Gram-positive)
*Positive For Growth, but colorless:*
-Gram-negative, but no lactose fermentation (noncoliform)
*Positive for growth and Lactose fermentation:*
-Pink growth and good growth indicates a Gram-negative bacteria and Lactose fermentation (coliform)
AcTUAL QUESTIONS AND cOrrEcTLY WELL DEFINED ANSWErS LATEST
ALrEADY GrADED A+
Oxidase Test - ANSWEr-*Positive Oxidase Test:*
-Turns blue within 20-30 seconds
*Negative Oxidase Test*
-No color change within thirty seconds
*Reagent used:*
-Oxidase
What is the purpose of the oxidase test? - ANSWEr--The tests is used to identify bacteria containing the
respiratory enzyme cytochrome c oxidase. Differentiate between enterobacteriaceae and
pseudomonadaceae
How is the oxidase test performed? - ANSWEr-1. Transfer bacterium to the paper
2. Add drops of complex A & B to bacterium
3. Observe for color change within 30 seconds
,Why should you read the results of the oxidase test within 30 seconds? - ANSWEr--The reagents of this
test are unstable, therefore they may oxidize independently due to exposure to air.
Catalase Test - ANSWEr-*Positive Catalase*
-Visible Bubble production
*Negative Catalase Test*
-No Bubbles
*Reagent Used:*
-Hydrogen Peroxide
Why is the Catalase Test Used? - ANSWEr--This test is used to identify organisms that produce the
enzyme catalase, and its ability to break down hydrogen peroxide. Differentiate between micrococci and
streptococci
How is the catalase test performed? - ANSWEr-1. Transfer a large amount of growth to slide
2. Place one to two drops of hydrogen peroxide on bacteria
3. Observe for bubbles
, MacConkey Test - ANSWEr-*Poor Growth or No growth:*
-Organism is inhibited by CV and/or bile, therefore is Gram-positive
*Good Growth:*
-Organism is not inhibited by CV and/or bile, therefore Gram-Negative
*Pink to red growth with or without bile precipitate:*
-Organism produces acid from lactose fermentation therefore is a probable coliform
*Growth is "colorless" (not red or pink):*
-Organism does not ferment lactose, therefore is a noncoliform
What does the bacteria look like on a MacConkey Media? - ANSWEr-*Negative Growth:*
-Streak lines visible, but no colonies (Gram-positive)
*Positive For Growth, but colorless:*
-Gram-negative, but no lactose fermentation (noncoliform)
*Positive for growth and Lactose fermentation:*
-Pink growth and good growth indicates a Gram-negative bacteria and Lactose fermentation (coliform)
