Microbiology biochemical identification tests flashcards

What does a catalase test determine?

It determines the presence of the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen.

True or False: A positive oxidase test indicates the presence of cytochrome c oxidase.

True. A positive oxidase test shows bacteria can use oxygen as a terminal electron acceptor.

Fill in the blank: The _____ test assesses an organism's ability to ferment glucose.

The Durham test assesses an organism's ability to ferment glucose.

Compare the methyl red and Voges-Proskauer tests.

Methyl red tests for mixed acid fermentation; Voges-Proskauer tests for butylene glycol fermentation.

What does the urease test measure?

It measures the ability of bacteria to hydrolyze urea into ammonia and carbon dioxide, raising pH.

Cause → Effect: A positive lactose fermentation test results in what?

A positive lactose fermentation test results in acid and gas production, often indicated by a color change.

What is the purpose of the citrate test?

The citrate test determines if an organism can utilize citrate as the sole carbon source, producing alkaline products.

True or False: A positive indole test shows tryptophan is metabolized.

True. A positive indole test indicates the breakdown of tryptophan into indole, which is detected by Kovac's reagent.

What does the H2S production test indicate?

It indicates the ability of bacteria to reduce sulfur compounds to hydrogen sulfide, visible as a black precipitate.

What does the nitrate reduction test evaluate?

It evaluates an organism's ability to reduce nitrate (NO3) to nitrite (NO2) or further to nitrogen gas (N2).

True or False: The fermentation test is only for carbohydrates.

False. The fermentation test can assess the fermentation of various substrates, including alcohols and amino acids.

What is a positive result in a phenol red broth?

A positive result is indicated by a color change to yellow due to acid production from fermentation.

Fill in the blank: The _____ test detects hydrogen sulfide production.

The triple sugar iron (TSI) test detects hydrogen sulfide production.

Cause → Effect: A negative citrate test leads to what?

A negative citrate test indicates that the organism cannot use citrate as its sole carbon source.

What does the bile esculin test determine?

It determines an organism's ability to hydrolyze esculin in the presence of bile, forming a dark complex.

What does the starch hydrolysis test check for?

It checks for the presence of amylase, which breaks down starch into simpler sugars.

What is the purpose of the Indole test?

To determine if an organism can produce indole from tryptophan.

True or False: The Methyl Red test detects alcohol fermentation.

False. It detects mixed acid fermentation, indicating a low pH.

What does a positive Citrate test indicate?

The organism can utilize citrate as its sole carbon source.

What is the function of the Voges-Proskauer test?

To detect acetoin production from glucose fermentation.

Fill in the blank: The _____ test is used to identify hydrogen sulfide production.

Triple Sugar Iron (TSI) test.

Compare Oxidase and Catalase tests.

Oxidase tests for cytochrome c oxidase; Catalase tests for hydrogen peroxide breakdown.

What is the significance of the Urease test?

To identify organisms that can hydrolyze urea into ammonia.

Cause → Effect: If an organism produces urease, then...

...the pH of the medium will increase, turning the indicator pink.

What does a positive Kligler’s Iron Agar test show?

Fermentation of glucose and/or lactose and H2S production.

What is the function of the API 20E system?

To identify Enterobacteriaceae using a series of biochemical tests.

True or False: The Fermentation test measures gas production.

True. It measures both acid and gas production from sugars.

What does a positive Bile Esculin test indicate?

The organism can hydrolyze esculin in the presence of bile.

How is the Malonate test conducted?

By checking for growth on malonate as the sole carbon source.

What does a positive Nitrate reduction test indicate?

The organism can reduce nitrate to nitrite or further products.

Fill in the blank: The _____ test is used to measure lactose fermentation.

Lactose fermentation test.

What does the H2S test indicate?

Presence of hydrogen sulfide production in a medium.

True or False: The Starch Hydrolysis test indicates protein breakdown.

False. It indicates starch breakdown into glucose.

What does the Carbohydrate fermentation test measure?

Ability to ferment specific carbohydrates producing acid or gas.

What is the purpose of the Esculin hydrolysis test?

To differentiate Enterococcus species based on esculin hydrolysis.

Compare the results of a positive and negative Gelatin test.

Positive: gelatin is liquefied; Negative: gelatin remains solid.

What does the catalase test detect?

The catalase test detects the presence of the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen.

True or False: All bacteria produce catalase.

False. Not all bacteria produce catalase; for example, anaerobic bacteria often lack this enzyme.

Fill in the blank: The ______ test checks for the enzyme urease.

urease

What does a positive urease test indicate?

A positive urease test indicates that the bacteria can hydrolyze urea into ammonia, raising the pH of the medium.

Compare oxidase and catalase tests.

Oxidase tests detect cytochrome c oxidase, while catalase tests detect catalase, which breaks down hydrogen peroxide.

What is the purpose of the indole test?

The indole test identifies bacteria that can produce indole from tryptophan via the enzyme tryptophanase.

Cause → Effect: Presence of cytochrome c oxidase → ?

Bacteria can use oxygen as a terminal electron acceptor in respiration.

What does the methyl red test measure?

The methyl red test measures the acidity of the medium, indicating mixed acid fermentation by the organism.

True or False: The citrate test indicates the ability to use citrate as a sole carbon source.

True. A positive citrate test shows that the organism can utilize citrate, producing alkaline byproducts.

What is the result of a positive phenylalanine deaminase test?

A positive result indicates the bacteria can deaminate phenylalanine to phenylpyruvic acid, detectable by ferric chloride.

Describe the gelatinase test.

The gelatinase test checks if bacteria can hydrolyze gelatin into amino acids, causing the medium to liquefy.

What enzyme does the starch hydrolysis test detect?

The starch hydrolysis test detects the enzyme amylase, which breaks down starch into simpler sugars.

What is the purpose of selective media?

Selective media allows growth of specific microorganisms while inhibiting others. Examples include: - MacConkey agar for Gram-negative bacteria - Mannitol salt agar for Staphylococci.

True or False: API 20E is used for gram-positive bacteria.

False. API 20E is specifically designed for the identification of Enterobacteriaceae and other gram-negative bacteria.

Fill in the blank: The _______ test identifies bacteria based on their ability to ferment lactose.

lactose fermentation.

What does the oxidase test indicate?

The oxidase test detects cytochrome c oxidase, indicating the ability to perform aerobic respiration. Positive result: purple color after adding reagent.

Comparison: Biochemical tests vs. Molecular tests

- Biochemical tests: rely on metabolic pathways. - Molecular tests: detect specific DNA or RNA sequences.

How does the urease test work?

The urease test checks for urease production. Bacteria that produce urease convert urea to ammonia, raising pH and changing color (pink).

What is the main application of the citrate utilization test?

The citrate utilization test assesses a bacterium's ability to use citrate as its sole carbon source. Positive result: growth and color change (usually blue).

Cause → Effect: Presence of indole production

Indole production indicates the breakdown of tryptophan. - Positive test: red ring after adding Kovac's reagent.