SIM Sulfur Biochemical Test Overview, Citrate Biochemical Test Overview, SIM Indole Biochemical Test Overview, Urease Biochemical Test Overview

What is the purpose of the SIM Sulfur Test?

To determine if bacteria can produce thiosulfate reductase and cysteine desulferase to break down sodium thiosulfate and cysteine.

What are the substrates used in the SIM Sulfur Test?

Sodium thiosulfate and cysteine.

What enzymes are produced by bacteria in the SIM Sulfur Test?

Thiosulfate reductase and cysteine desulferase.

What does thiosulfate reductase break down?

Sodium thiosulfate to form hydrogen sulfide.

What does cysteine desulferase break down?

Cysteine to form hydrogen sulfide.

What is the indicator used in the SIM Sulfur Test?

Iron.

What reaction occurs when hydrogen sulfide combines with iron?

It produces sulfuric acid and ferrous sulfide.

What is the significance of the black precipitate in the SIM Sulfur Test?

It indicates a positive result, showing that bacteria can produce thiosulfate reductase and cysteine desulferase.

What does a positive result in the SIM Sulfur Test look like?

A black precipitate due to ferrous sulfide.

What indicates a negative result in the SIM Sulfur Test?

No black precipitate, indicating no formation of ferrous sulfide.

What happens when there is no hydrogen sulfide produced in the SIM Sulfur Test?

Iron has nothing to combine with, resulting in no sulfuric acid or ferrous sulfide formation.

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

Black, due to ferrous sulfide.

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

No color change, as there is no formation of ferrous sulfide.

What are the products formed in the SIM Sulfur Test?

Hydrogen sulfide, sulfuric acid, and ferrous sulfide.

What does the presence of hydrogen sulfide indicate in the SIM Sulfur Test?

That the bacteria can break down either sodium thiosulfate or cysteine.

What is the role of sodium thiosulfate in the SIM Sulfur Test?

It serves as a substrate for thiosulfate reductase.

What is the role of cysteine in the SIM Sulfur Test?

It serves as a substrate for cysteine desulferase.

What is the outcome if bacteria cannot produce thiosulfate reductase or cysteine desulferase?

The test will be negative, showing no black precipitate.

How is the black precipitate formed in the SIM Sulfur Test?

By the combination of hydrogen sulfide with iron.

What is the significance of sulfuric acid in the SIM Sulfur Test?

It is produced when hydrogen sulfide combines with iron, contributing to the test's results.

What is the purpose of the Citrate Test?

To determine if bacteria can produce citrate permease to move citrate into the cell and citrase to break down citrate.

How is citrate moved into the bacterial cell?

Citrate is moved into the bacterial cell via citrate permease.

What is the reaction catalyzed by citrase?

Citrate is broken down into pyruvate.

What are the substrates involved in the Citrate Test?

Citrate and ammonium phosphate.

What enzymes are produced by bacteria after inoculation in the Citrate Test?

Citrate permease and citrase.

What is the role of citrate permease in bacteria?

It makes the bacteria more permeable to citrate, allowing citrate to be moved into the cell.

What is the indicator used in the Citrate Test?

Bromothymol blue.

What color change occurs in bromothymol blue due to pH changes?

It changes from forest green (acidic) to royal blue (basic).

What products are formed when citrase breaks down citrate?

Pyruvate.

What products are formed when bacteria use ammonium phosphate?

Ammonia and ammonium hydroxide.

What effect does ammonia production have on pH in the Citrate Test?

It turns the pH basic, resulting in a color change of bromothymol blue.

What indicates a positive result in the Citrate Test?

A royal blue color due to a basic pH from ammonia production.

What does a positive result indicate about the bacteria?

The bacteria can produce citrate permease and citrase, allowing them to utilize citrate and ammonium phosphate.

What indicates a negative result in the Citrate Test?

A forest green color due to no change in pH.

What does a negative result indicate about the bacteria?

The bacteria cannot produce citrate permease or citrase.

What happens to the color of bromothymol blue if ammonia is not produced?

The color remains forest green.

What is the significance of pyruvate in the Citrate Test?

It is the product formed when citrase breaks down citrate.

What happens to the pH when bacteria continue to grow and use ammonium phosphate?

The pH becomes basic due to ammonia production.

What color does bromothymol blue turn in a basic environment?

Royal blue.

What is the initial color of bromothymol blue before inoculation?

Forest green.

What is the purpose of the SIM Indole Test?

To determine if bacteria can produce tryptophanase to break down tryptophan.

What substrate is used in the SIM Indole Test?

Tryptophan, which is already present in the agar deep before inoculation.

What enzyme do bacteria need to produce for the SIM Indole Test?

Tryptophanase.

What are the products of the breakdown of tryptophan by tryptophanase?

Indole and pyruvate.

What reagent is added to the SIM Indole Test after inoculation?

Kovac's reagent.

What does Kovac's reagent produce when it combines with indole?

A red ring.

What indicates a positive result in the SIM Indole Test?

The presence of a red ring, indicating that the bacteria can produce tryptophanase.

What indicates a negative result in the SIM Indole Test?

The absence of a red ring, indicating that the bacteria cannot produce tryptophanase.

Why does a negative result show no red ring?

Because without indole, Kovac's reagent has nothing to combine with to produce the red ring.

What is the significance of indole in the SIM Indole Test?

Indole is produced when tryptophanase breaks down tryptophan and combines with Kovac's reagent to indicate a positive result.

Urease Test

broth to determine if bacteria can produce urease to break down urea

Substrate

urea

Enzyme

urease

Indicator

phenol red

Products

ammonia + carbon dioxide

Positive

hot pink

Negative

yellow

pH change

acid/yellow, base/hot pink, neutral/red

Ammonia production

turns the pH basic resulting in a color change of phenol red in the broth

Color change indication

indicates the bacteria can produce urease to break down urea