Microbial Metabolism and Carbohydrate Catabolism
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Questions and Answers

Butyric acid and propionic acid are produced from starch by what process?

  • Deamination of amino acids
  • Decarboxylation of amino acids
  • Anaerobic respiration
  • Fermentation (correct)

How do bacteria produce indole from tryptophan?

  • Anaerobic Respiration
  • Decarboxylation of amino acids
  • Desulfurization of amino acids
  • Deamination of amino acids (correct)

What is the purpose of the Durham tube in a fermentation tube?

  • To trap any gas produced during fermentation (correct)
  • To provide a surface for bacterial growth
  • To measure the pH of the medium
  • To introduce oxygen into the tube

How do bacteria produce $H_2S$ from cysteine and methionine?

<p>Desulfurization of amino acids (B)</p> Signup and view all the answers

What color does phenol red turn in an acidic environment and what approximate pH does this indicate?

<p>Yellow; pH of 6.8 or below (A)</p> Signup and view all the answers

In the Methyl Red (MR) test, what color indicates a positive result (large amount of organic acid production, pH below 4.4) after the addition of methyl red?

<p>Red (D)</p> Signup and view all the answers

Which type of enzyme functions by breaking down large substrates into smaller components through the addition of water?

<p>Exoenzyme (A)</p> Signup and view all the answers

What is the primary function of amylase?

<p>To hydrolyze starch into smaller carbohydrates (B)</p> Signup and view all the answers

The MRVP broth is used to distinguish organisms based on what?

<p>Whether they produce large amounts of acid or neutral products from glucose (C)</p> Signup and view all the answers

What chemical ratio is characteristic of carbohydrates?

<p>$(CH_2O)_n$ (B)</p> Signup and view all the answers

During prolonged incubation, bacteria may start growing on peptone after exhausting the carbohydrate. What effect does this typically have on the pH indicator?

<p>It causes neutralization of the indicator, turning it red due to ammonia production. (D)</p> Signup and view all the answers

Which of the following is NOT a typical characteristic of monosaccharides?

<p>Composed of two to about 20 sugar molecules (B)</p> Signup and view all the answers

Which of the following best describes the purpose of studying microbial metabolism?

<p>To identify bacteria based on their biochemical characteristics and understand their ecological roles. (B)</p> Signup and view all the answers

Which type of bacteria produce short-chain fatty acids that provide energy for human colonic cells?

<p>Intestinal bacteria (C)</p> Signup and view all the answers

What is the term for chemical reactions that release energy from the breakdown of complex organic molecules?

<p>Catabolism (D)</p> Signup and view all the answers

What are the 'biologic characters' of bacteria, as referenced in the excerpt?

<p>Information about their metabolic processes and activities. (D)</p> Signup and view all the answers

What is the primary function of enzymes in metabolic processes?

<p>To catalyze or speed up biochemical reactions. (B)</p> Signup and view all the answers

What is the main difference between endoenzymes and exoenzymes?

<p>Endoenzymes function inside the cell, while exoenzymes are released to catalyze reactions outside the cell. (C)</p> Signup and view all the answers

Why is metabolism used as a factor to identify bacteria?

<p>Many bacteria share similar colony and cell morphology, making metabolism a useful differentiating characteristic. (B)</p> Signup and view all the answers

What does the study of microbial metabolism help us understand about microbes?

<p>Their roles in various ecological processes. (C)</p> Signup and view all the answers

In the context of the human large intestine, what role does bacterial metabolism play?

<p>It affects host intestinal function and health. (C)</p> Signup and view all the answers

What is the primary function of oxidative catabolism in bacteria?

<p>To produce carbon dioxide and water (A)</p> Signup and view all the answers

What does fermentative catabolism not require?

<p>Molecular oxygen (D)</p> Signup and view all the answers

How can you determine whether an organism is oxidative or fermentative?

<p>Using OF basal media (D)</p> Signup and view all the answers

What does the yellow color in OF medium indicate?

<p>Catabolism of the carbohydrate (B)</p> Signup and view all the answers

What occurs in the sealed tube of the OF medium if an organism is oxidative?

<p>No acid production (B)</p> Signup and view all the answers

What role does bromthymol blue play in the OF medium?

<p>It indicates pH changes (D)</p> Signup and view all the answers

What is the metabolic end-product of fermentation?

<p>Small organic molecules (B)</p> Signup and view all the answers

What is the purpose of flooding the starch agar plate with Gram's iodine?

<p>To detect starch hydrolysis (C)</p> Signup and view all the answers

Which bacterium is assigned a BSL-2 classification in the procedures?

<p>Pseudomonas aeruginosa (D)</p> Signup and view all the answers

In the context of OF medium, what does dark blue coloration indicate?

<p>Alkaline conditions due to peptone usage (B)</p> Signup and view all the answers

What technique is essential for inoculating the OF-glucose tubes?

<p>Inoculating loop and needle technique (A)</p> Signup and view all the answers

Which of the following describes the characteristic of a fermenter in OF medium?

<p>Produces acid in both tubes (D)</p> Signup and view all the answers

What type of agar is used in OF medium?

<p>Nutrient semisolid agar (D)</p> Signup and view all the answers

What indicates that starch has been hydrolyzed on the starch agar plate?

<p>A clear zone around the bacteria (A)</p> Signup and view all the answers

Which of the following bacteria can be used for inoculating the OF-glucose media?

<p>Escherichia coli (C)</p> Signup and view all the answers

What is the primary incubation temperature for the bacterial plates and tubes during the experiment?

<p>35°C (D)</p> Signup and view all the answers

After the first incubation period, how should the plates be stored if they are not examined immediately?

<p>In the refrigerator at 5°C (C)</p> Signup and view all the answers

What type of test can be further conducted once a bacterium is determined to be fermentative by the OF test?

<p>Carbohydrate fermentation tests (B)</p> Signup and view all the answers

What addition is made to one OF-glucose tube to create an anaerobic environment?

<p>Mineral oil (A)</p> Signup and view all the answers

Which type of starch hydrolysis result indicates that the starch has remained unchanged?

<p>Dark blue color around bacteria (D)</p> Signup and view all the answers

Flashcards

Carbohydrate Catabolism

The biochemical process of breaking down carbohydrates to release energy.

Fermentation

An anaerobic process that converts sugars to acids, gases, or alcohol.

Protein Catabolism

The process of breaking down proteins into amino acids and smaller molecules.

Respiration

Metabolic process that produces energy by breaking down glucose with oxygen.

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Metabolism

All the chemical reactions in a living organism necessary for maintaining life.

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Endoenzymes

Enzymes that function within a cell to catalyze biochemical reactions.

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Exoenzymes

Enzymes secreted outside the cell to catalyze reactions on larger molecules.

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Intestinal bacteria

Bacteria in the gut that aid digestion and produce metabolites.

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Short-chain fatty acids

Fatty acids like butyric and propionic acid produced by bacteria from carbohydrates.

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Fecal odors

Odors from feces caused by substances like indole and H2S from protein breakdown.

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Amylase

An exoenzyme that hydrolyzes starch into smaller carbohydrates.

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Oligosaccharides

Carbohydrates made of 2 to 20 monosaccharides.

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Hydrolysis

A chemical reaction involving the addition of water to break down molecules.

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Monosaccharides

Simple sugars containing 3 to 7 carbon atoms.

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Polysaccharides

Carbohydrates consisting of 20 or more monosaccharide units.

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Fermentation Tubes

Used to detect acid and gas production from carbohydrates in bacteria.

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Phenol Red Indicator

An acid-base indicator that changes color in response to pH alterations during fermentation.

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Methyl Red Test

A test to determine if a bacterium produces a lot of organic acid from glucose, resulting in a red color.

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Voges-Proskauer Test

Used to detect the presence of neutral end products like acetoin, indicated by a color change to yellow.

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Gas Trapping in Durham Tube

This inverted tube traps gas produced during fermentation, indicating microbial activity.

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Oxidative Catabolism

The breakdown of glucose in the presence of oxygen, producing CO2 and water.

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Fermentative Catabolism

The breakdown of glucose without oxygen, producing organic acids.

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OF Medium

A nutrient agar deep for testing glucose metabolism in bacteria.

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Bromthymol Blue

A pH indicator in OF medium that turns yellow in acidic conditions.

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Acid Production

Occurs when glucose is metabolized, indicated by color change in OF medium.

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Alkaline Conditions

Indicated by a dark blue color due to ammonia from peptone use.

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Aerobic Conditions

Conditions requiring oxygen for bacterial growth and metabolism.

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Anaerobic Conditions

Conditions where bacteria grow without the presence of oxygen.

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Metabolic End-Products

The small organic molecules produced from fermentation.

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Starch Hydrolysis

The breakdown of starch into sugars by enzymes produced by microorganisms.

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Gram's Iodine

A reagent used to detect the presence of starch by forming a blue complex.

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OF-Glucose Test

A test to determine if bacteria can ferment glucose in aerobic or anaerobic conditions.

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Pseudomonas aeruginosa

A bacterial species commonly tested for its ability to metabolize sugars.

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Aseptic Technique

Methods used to prevent contamination during microbial procedures.

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Incubation Temperature

The optimal temperature (35°C) for bacteria to grow during tests.

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Bacillus subtilis

A common soil bacterium used in laboratory exercises.

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Micrococcus luteus

A yellow-pigmented bacterium used in biochemical testing.

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Starch Agar

A nutrient medium used to test for starch hydrolysis by bacteria.

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Study Notes

Microbial Metabolism

  • Microbial metabolism refers to the chemical reactions within organisms, catalyzed by enzymes
  • Early bacterial classification relied solely on morphology
  • Biologic characters, including metabolism, are now crucial for classification
  • Metabolism includes all reactions within living organisms, primarily involving enzymes inside cells (endoenzymes) or released outside (exoenzymes)
  • Enzymes catalyze biochemical reactions
  • Studying bacterial metabolism is essential to understand their role in ecology and disease

Carbohydrate Catabolism

  • Carbohydrates are a primary source of energy for bacteria
  • Catabolism involves breaking down complex carbohydrates into simpler sugars like glucose
  • Glucose can be oxidized (using oxygen) or fermented (without oxygen) for energy
  • Oxidative catabolism generates CO2 and water, whereas fermentation produces organic acids or other products
  • Bacteria can be identified based on their carbohydrate fermentation patterns

Fermentation & Gas Production

  • Fermentation is used by some bacteria to generate energy anaerobically from glucose.
  • Acidic products are often produced
  • Gas production can occur as a byproduct of fermentation
  • Gas production can be identified using a tube designed to capture the gas formed.

Differential Media for Microbial Identification

  • Differential media are used to distinguish between different types of bacteria based on their metabolic activities
  • Example media like Starch Agar or OF-glucose media are used to identify bacteria by their ability to use carbohydrates or to produce acid or gas
  • Indicator dyes like bromthymol blue can indicate acidity or alkalinity in growth media
  • Specific biochemical tests help identify bacteria based on specific metabolic reactions like producing certain acids or gases

Key Metabolic Processes

  • Anaerobic respiration, deamination of amino acids, decarboxylation of amino acids, desulfurization of amino acids are examples of metabolic processes in bacteria
  • These processes are crucial for producing energy and for synthesizing components needed by bacteria

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Description

This quiz covers key concepts in microbial metabolism and the catabolism of carbohydrates. It explores the biochemical reactions catalyzed by enzymes in bacteria, essential for their classification and ecological roles. Understanding how bacteria process carbohydrates is crucial for recognizing their energy sources and fermentation patterns.

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