Biochemistry - Sodium Citrate Quiz

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Questions and Answers

What is the primary nitrogen source in Simmon’s Citrate agar?

Urea

Ammonium ion (NH4+) (correct)

Nitrate

Nitrogen gas

In the methyl red test, what is indicated by a pH change that results in a color change of the media?

High acid content production (correct)

A neutral pH environment

Low sugar concentration

The absence of acid production

What color indicates a positive result in the oxidase test?

Green

Red

Bluish purple (correct)

Yellow

Which one of these bacteria is identified as having a positive oxidase test?

Pseudomonas aeruginosa Signup and view all the answers

What role does carbon dioxide play in the process described for bacteria oxidizing citrate?

It reacts with sodium and water to form carbonate. Signup and view all the answers

What type of bacteria does Acridine Orange bind to?

Both gram-positive and gram-negative bacteria Signup and view all the answers

What is the LPS content in bacteria that lack an outer membrane?

Virtually low Signup and view all the answers

How does Calcofluor White function in lab practices?

Binds to chitin in fungal cell walls Signup and view all the answers

In which pathway is glucose converted to pyruvic acid?

Embden-Meyerhof-Parnas (EMP) Glycolytic Pathway Signup and view all the answers

What is the significance of methylene blue in microbiological techniques?

Counterstains in acid-fast staining procedures Signup and view all the answers

Which substance is used to absorb water formed when hydrogen combines with free oxygen?

Silica gel Signup and view all the answers

What does fermentation primarily produce in anaerobic conditions?

Lactic acid Signup and view all the answers

What are metachromatic granules observed in?

Corynebacterium diphtheriae Signup and view all the answers

What is the purpose of palladium catalyst pellets in anaerobic culture conditions?

To remove residual oxygen Signup and view all the answers

Which of the following substances prevents swarming of Proteus species?

Alcohol Signup and view all the answers

What is used to observe WBC in stool samples?

Acridine Orange Signup and view all the answers

What should be done with media types except thioglycolate broth for storage?

Store in the refrigerator Signup and view all the answers

Which of the following organisms requires a blood culture duration of 7-10 days?

Anaerobes Signup and view all the answers

Which selective medium substance inhibits the growth of gram-positive organisms?

Sodium deoxycholate Signup and view all the answers

What is the recommended timeframe to hold cultures for final diagnosis?

Several weeks, depending on organism Signup and view all the answers

Which of the following substances does not inhibit gram-negative organisms?

Alcohol Signup and view all the answers

What is the main purpose of polymerase chain reaction (PCR) in molecular diagnosis?

To amplify nucleic acids for better detection Signup and view all the answers

Which type of PCR allows for the quantification of nucleic acids after each replication cycle?

Real-time PCR Signup and view all the answers

What does the Taq polymerase do in conventional PCR?

It amplifies the DNA sequence Signup and view all the answers

What is a significant advantage of real-time PCR compared to conventional PCR?

It combines amplification and detection in one process Signup and view all the answers

In what applications can conventional PCR be utilized?

Microbial detection, gene analysis, and DNA profiling Signup and view all the answers

Which type of stain is used to visualize bacterial capsules?

Capsular Stain Signup and view all the answers

Which of the following bacteria species is known to produce hydrogen sulfide (H2S) in Kligler’s Iron Agar?

Salmonella Signup and view all the answers

What does a positive result for gas production indicate in Kligler’s Iron Agar?

Presence of glucose fermentation Signup and view all the answers

Which of the following bacilli are considered gram positive?

Corynebacterium Signup and view all the answers

Which bacteria are incapable of fermenting glucose and therefore cannot utilize lactose?

Proteus Signup and view all the answers

Which statement is true regarding all cocci?

All are gram positive except for Neisseria. Signup and view all the answers

Which of these types of stains is classified as an indirect stain?

Negative Stain Signup and view all the answers

What type of media is Kligler’s Iron Agar primarily used to differentiate?

H2S producers from non-H2S producers Signup and view all the answers

Study Notes

Sodium Citrate (Simmon’s Citrate Agar)

Uses citrate as a carbon source and NH4+ as a nitrogen source.
Bacterial oxidation of citrate liberates CO2, which combines with Na and H2O to form carbonate, raising the pH.
Color change due to bromothymol blue indicates positive results.

Methyl Red Test

Assesses the ability of microbes to oxidize glucose with high acid end product stabilization.
Media used includes MRVP Broth or Clark Lubbs Broth.
Methyl red serves as a pH indicator, with a positive result indicating a low pH.

Oxidase Test

Utilizes reagent dyes that act as artificial electron acceptors substituting for oxygen.
A colorless reduced state indicates no cytochrome oxidase presence, while bluish-purple color indicates a positive result for Pseudomonas aeruginosa.

Acridine Orange

Stains both living and dead gram-positive and gram-negative bacteria.
Binds to nucleic acid, allowing fluorescent microscopy for detection.
Useful in visualizing bacteria in blood cultures.

Methylene Blue

Observes metachromatic granules in Corynebacterium diphtheriae.
Serves as a counterstain in acid-fast staining procedures.
Detects WBCs in stool samples, differentiating bacterial groups.

Anaerobic Utilization of Pyruvic Acid Fermentation

Involves hydrogen and CO2 gas production, promoting anaerobe growth.
Uses palladium catalyst pellets to eliminate residual oxygen and silica gel to absorb formed water.

Selective Media

Inhibitory substances: sodium deoxycholate, bile salts prevent gram-positive organisms; potassium tellurite and sodium azide inhibit gram-negative organisms.
Special growth media includes lactose fermenters like Escherichia and Enterobacter.

Gram Staining General Rules

All cocci are gram-positive except Neisseria and related genera; all bacilli are gram-negative except specific exceptions like Mycobacteria.
Higher organisms like actinomycetes and yeasts are gram-positive; all spiral organisms reported as gram-negative.

Polymerase Chain Reaction (PCR)

Amplifies nucleic acids for rapid detection of target microorganisms.
Conventional PCR utilizes Taq polymerase for amplification; applicable in microbial detection and gene analysis.
Real-time PCR quantifies target nucleic acid during replication using fluorescent dyes, combining amplification and product detection simultaneously.

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Description

Test your knowledge on sodium citrate as a carbon source and its role in Simmon's Citrate agar. Understand the metabolic processes involved when bacteria oxidize citrate and the implications on CO2 release and nitrogen sources. Perfect for students studying microbiology or biochemistry.