Maxin’s Enzyme Exam 2 – Flashcards

Gelatin Hydrolysis

;

or

;

Gelatin hydrolase

;

or;

;

Gelatinase

Starch negative

;

(The organism did not break down the starch into glucose)

Starch positive

;

(The organism has the amylase enzyme which broke down the starch into glucose)

Cysteine positive +

;

An anaerobe

;

(The organism contains the enzyme cysteine desulfhydrase which breaks down cysteine to yield Hydrogen Sulfide (H₂S) which reacts with the iron in the agar to form a black precipitate.)

;

;

;

;

Cysteine is an amino acid that contains sulfur.

;

(Think CySteine) S = Sulfur

Urea positive

;

(The organism contains urease which breaks down the Urea into ammonia (NH₃OH). ;Since ammonia is alkaline/basic, it turns the phenol red within the broth hot pink.)

Urea negative -

;

(Phenol red in the broth turns yellow in acidic conditions, meaning the organism lacks the ability (enzyme: urease) into ammonia.)

1. Nitrate positive

;

2. Nitrite (NO₂)

1. Nitrite (NO₂) positive

;

2. Ammonia (NH₃ or N₂)

;

(Nitrite reductase within the organism broke down Nitrite to Ammonia which combined with Nesslers to form Ammonium, the brown precipitate)

Nitrate positive

;

Nitrite negative

Nitrate reductase

;

and;

;

Nitrite reductase

Gelatin hydrolase

;

(Gelatin hydrolase breaks down the gelatin so the conents of the tube can no longer solidify and so they remain liquid)

Carbohydrate Fermentation

(Carbohydrase) Test

;

;

Lactase

;

Acid and Gas

;

(The organism is lactose positive + for acid and gas)

Lactase

;

Acid only

;

(Organism is Lactose positive for acid)

Dextrase

;

Acid and Gas

;

(Organism is dextrose positive +)

Trick question:

;

The organism is Sucrose negative - it does not contain sucrase and thefore could not break down the sucrose into acids nor gas.

;

• Indole (Tryptophanase)
• Methyl Red;
• Voges-Proskauer (Butanediol Dehydrogenase)
• Citrate Utilization (Citrase)

;

1. Indole

2. Tryptophanase

IMViC

Methyl Red (MR)

;

and;

;

Voges-Proskauer (VP)

Dextrose positive +

;

Acid

1. alphanaphthol

2. potassium hydroxide (KOH)

;

Voges-Proskauer (VP)

Butanediol positive +

;

Acetyl methyl carbionl (Acetoin)

MR test identifies organisims that make strong acids

VP test identifies organisims that make weak acids

;

(The weak acids are more neutral, but still acidic)

;

"MR. Strong, meet VP weak"

pH ; 7.6

"pH is less than 7.6"

;

Products range from neutral to acidic

pH ; 7.6

"pH is greater than 7.6"

;

The products range from neutral to basic/alkaline

1) Citrate positive

2) Citrase

;

(Lots of coliforms (bacteria that grow in the colon) produce a lot of alkaline products. ;Bromthymol indicator turns blue in presence of alkaline products.)

"Dehydrogenperoxidease"

;

It breaks down hydrogen peroxide (de-) and is an enzyme (-ase)

Hydrogen peroxide or Catalase positive +

;

Bubbles are Oxygen (O₂₎

Hydrogen peroxide or catalase negative -

;

1. Gram's Crystal Violet (Primary Stain)
2. Gram's Iodine (Mordant)
3. Ethyl Alcohol (Decolorizer)
4. Gram's Safranin (Counterstain)

Retain the primary

Lose the secondary

;

(Gram + bacteria are blue/violet due to Gram's crystal violet

Lose the primary stain

Retain the counter/secondary stain

;

(Gram - bacteria are red because they retain the Safranin counter stain)

Litmus is red in acids

Litmus is blue in bases

The organism contains lactase which broke down (fermented) the lactose and made acids.

The organism is lactose positive +

The organism does not contain lactase so the lactose was not fermented

The organism is lactose negative -

The organism contains casein hydrolase which broke down the casein protein in the milk.

The organism is casein +

The organism has reduced the litmus. ;The white is the milk.

Organism is Casein negative -

Hemolysin

;

exo-enzyme

Hemolytic +

Beta Hemolytic

;the Zone of inhibition

;

Sensitive

Nitrite Reductase

;

HCl

Sulfanilic acid 

and

Dimethylalphanaphthylamine