Biochemistry I Differential Tests

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Questions and Answers

Which organism is NOT listed under the Phenol Red Broth results?

Staphylococcus aureus (correct)

Enterococcus faecalis

Pseudomonas aeruginosa

Escherichia coli

Which test utilizes a slant medium and indicates hydrogen sulfide production?

Simmons Citrate Test

Utilization of Malonate Test

Carbohydrate Fermentation Test

Triple Sugar–Iron Agar Test (correct)

Which of the following organisms can ferment lactose?

Escherichia coli (correct)

Orphan

Proteus vulgaris

Pseudomonas aeruginosa

Which test specifically assesses an organism's ability to utilize malonate?

Malonate Broth Test Signup and view all the answers

In the IMViC tests, which organism is associated with the Methyl Red Test?

Escherichia coli Signup and view all the answers

Which of the following organisms is NOT identified in the Simmons Citrate Test?

Orphan Signup and view all the answers

What is the primary function of the Triple Sugar Iron Agar Test?

Detect hydrogen sulfide and gas production Signup and view all the answers

Which organism is most likely to produce hydrogen sulfide in the Triple Sugar–Iron Agar Test?

Salmonella spp Signup and view all the answers

What color change indicates a positive result in the malonate test?

Blue Signup and view all the answers

Which bacteria is used as the negative control in the malonate test?

E. coli Signup and view all the answers

What is the principle of the malonate test?

The organism can utilize malonate as a carbon source. Signup and view all the answers

What does a result of yellow in the phenol red indicating test signify?

Acidic pH Signup and view all the answers

Which of the following indicates a neutral pH in the phenol red test?

Red Signup and view all the answers

Which enzyme is involved in the process of fermentation noted in the phenol red basics?

Glycolytic enzymes Signup and view all the answers

What is the effect of ammonia (NH3) release by bacteria on the pH of the media?

It raises the pH. Signup and view all the answers

What is the role of bromthymol blue in the malonate test?

To monitor pH changes. Signup and view all the answers

Study Notes

Differential Tests 1

Various tests used to determine bacterial characteristics.
Carbohydrate Fermentation tests include:
- Triple Sugar-Iron Agar
- IMVIC Test
- Hydrogen Sulfide Test
- Malonate Utilization

General Enzymatic Action

Enzymes act on substrates (e.g., sucrose, composed of glucose and fructose).
Substrate binding to the enzyme forms an enzyme-substrate complex.
Enzyme strain on the substrate bond causes breakage.
Products are released.
Enzyme is free to bind more substrate.

Biochemistry I

Various broth and agar tests used for bacterial identification.
Specific tests like Phenol Red (PR), Base Broth, Glucose Broth (GLU), Lactose Broth (LAC), and Sucrose Broth (SUC).
Methyl Red/Voges-Proskauer(MRVP) Broth
SIM (SIM Stab)
Triple Sugar Iron Agar (TSI)
Simmons Citrate (SC)
Malonate Broth (MAL)

Malonate Test

Tests if an organism can use malonate as a sole carbon source.
Positive result: Media alkalinizes, pH indicator (bromthymol blue) changes from green to blue.
Negative control: E. coli
Positive control: Enterobacter aerogenes

Phenol Red Basics

Phenol Red: pH indicator in media.
Pink at alkaline pH (>7.4)
Red at neutral pH (6.9-7.3)
Yellow at acidic pH (<6.8)
Fermentation of carbohydrate lowers pH (yellow).
Protein use raises pH (pink).
Durham tubes trap gas created during fermentation.
Alkaline reversion: Medium turns yellow initially, then red.

Triple Sugar Iron Agar

Contains three fermentative sugars (lactose, sucrose, glucose).
pH changes via fermentation.
Different color combinations indicate fermentation results.
Blackening (H₂S) and gas production are observed in the agar. -Example of Escherichia coli, Salmonella, and Proteus vulgaris

IMVIC Tests

Abbreviation for four biochemical tests (Indole, Methyl Red, Voges-Proskauer, Citrate).
Identifying and differentiating bacteria.
Useful with Gram-negative Enterobacteriaceae.

Methyl Red/Voges-Proskauer Test

Used for Mixed Acid Fermentation and 2,3-Butanediol Fermentation.
Uses MRVP broth. -Use plastic pipette measure about 1 mL for each sample. -Label the tubes

Mixed Acid Fermentation (Methyl Red)

Detects stable acid end products.
Indicator (methyl red) turns pink/red at acidic pH (<4.4).
Yellow: at neutral/alkaline (>7.2).
Orange: intermediate pH (4.4-6.2).
Positive result: pink/red color
Negative result: green/brown color

2,3-Butanediol Fermentation (Voges-Proskauer (VP))

Detects acetoin (precursor to 2,3-butanediol and ethanol).
Barritt's reagents (a-naphthol and KOH) are added to detect acetoin.
Positive result: red color.
Negative result: no color change/copperish discoloration.

Simmons Citrate Utilization Test

Tests if an organism uses sodium citrate as a carbon source.
Positive result: Medium turns deep blue.
Negative result: Medium remains green.
Indicator: Bromothymol blue.

SIM Medium (Sulfur, Indole, Motility)

Tests for sulfur reduction, indole production, and motility.
Black precipitate: sulfur reduction.
Kovac's reagent: detects indole.
Motility: Growth throughout the agar.

Carbohydrate Inoculations

Phenol Red is used to determine carbohydrate fermentation types.
Tests with different sugars (Glucose, Lactose, Sucrose).

Carbohydrate Fermentation

Organisms classify based on their ability to utilize/ferment specific carbohydrates.
Classification based on acid/gas production (A/-, A/G).

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Description

Explore various differential tests utilized in Biochemistry I to identify bacterial characteristics. This quiz covers carbohydrate fermentation tests, enzymatic action, and other broth and agar tests essential for microbial identification. Test your knowledge on methods like Triple Sugar-Iron Agar and Malonate Utilization.