Microbiology Lab 9 Quiz Review

Vocabulary-style flashcards covering biochemical tests for bacteria identification, including fermentation, digestion, and the SIM test series.

What is the Carbohydrate Fermentation Broth Indicator?

Bromocresol Purple

What does a yellow color indicate with Bromocresol Purple?

indicates a positive result, meaning acid was produced.

What does a purple color indicate with Bromocresol Purple?

indicates a negative result, meaning no acid was produced.

Durham tube

A tube used in carbohydrate fermentation to detect gas production; a bubble indicates gas was produced, while no bubble indicates no gas.

Amylase

The enzyme of interest in Starch Digestion that breaks down starch into simple sugars.

Gram's Iodine

The reagent used in the Starch Digestion test to determine if bacteria can digest starch.

The enzyme of interest in DNA Digestion

DNase

Breakdown in DNA Digestion

$DNA \rightarrow Nucleotides$.

What is the indicator used for the DNA Digestion test.

Methyl Green

What does a positive result look like with Methyl Green?

a clear zone around the colony.

What does a negative result look like with Methyl Green?

the medium staying blue-green.

Catalase

The enzyme of interest for the catalase test that breaks down hydrogen peroxide ($H_2O_{2}$) into water ($H_2O$) and oxygen ($O_{2}$).

The reagent used for the Catalase Test

Hydrogen Peroxide

What indicates a positive result in the Catalase Test?

the formation of bubbles (Oxygen gas).

What indicates a negative result in the Catalase Test?

no bubbles are formed

Breakdown that occurs during the catalase test

H₂O₂ —> H₂O + O₂

SIM Test

A combination medium used to test for Sulfur (S), Indole (I), and Motility (M).

The enzyme of interest in the Sulfur portion of the SIM test

Cysteine desulfurase

Breakdown of Cysteine desulfurase

$Cysteine \rightarrow H_2S$.

What indicates a positive result for Sulfur in the SIM Test?

the formation of a black precipitate in the SIM medium

What indicates a negative result for Sulfur in the SIM Test?

no black color.

The enzyme of interest in the Indole portion of the SIM test

Tryptophanase

Breakdown that occurs during Indole part of SIM test

$Tryptophan \rightarrow Indole$.

What is Kovac's Reagent

The reagent added to the SIM test to detect Indole.

What indicates a positive result with Kovac's Reagent?

a red layer (or ring) on top.

What indicates a negative result with Kovac's Reagent?

a yellow layer on top.

Motility Positive Result

cloudy growth throughout the tube in SIM medium

Motility Negative Result

growth only on the stab line.

Urease

The enzyme that breaks down Urea into $Ammonia + CO_{2} + H_2O$.

The indicator used in Urea Digestion

Phenol Red

What indicates a positive result in Urea Digestion using Phenol Red?

turns the Phenol Red indicator bright pink.

What indicates a negative result in Urea Digestion using Phenol Red?

turns the Phenol Red indicator orange/yellow color.

What indicates Starch Digestion?

a clear zone around the colony after adding Gram's Iodine.

What does a negative result in Starch Digestion look like?

A negative result for Starch Digestion is indicated by dark brown/black around the colony.

Enzymes of Interest for Carbohydrate Fermentation

Glucose, Lactose, Sucrose