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Questions and Answers
In a differential media, what indicates the type of metabolism occurring?
In a differential media, what indicates the type of metabolism occurring?
- The complete inhibition of growth of all non-desired bacteria.
- Changes in the color of pH indicators, by-product formation, or clearing of the media. (correct)
- The enhancement of growth of desired bacteria only.
- The presence of a specific chemical indicator that inhibits bacterial growth.
What is the purpose of selective media in microbiology?
What is the purpose of selective media in microbiology?
- To enhance the growth of all types of microorganisms.
- To inhibit the growth of some organisms while enhancing the growth of others. (correct)
- To provide a nutritionally rich environment for fastidious organisms.
- To distinguish between different types of bacterial metabolism.
What is the main characteristic of enrichment media?
What is the main characteristic of enrichment media?
- It contains high concentrations of salt to select for halophiles.
- It enhances the growth of desired bacteria while also allowing other bacteria to grow. (correct)
- It inhibits the growth of all organisms except the desired bacteria.
- It changes color to indicate which bacteria are growing.
What is the role of exoenzymes in bacterial metabolism?
What is the role of exoenzymes in bacterial metabolism?
What is the function of endoenzymes in bacterial cells?
What is the function of endoenzymes in bacterial cells?
What is the end-product of breaking down simple sugars using an endoenzyme inside a bacterial cell?
What is the end-product of breaking down simple sugars using an endoenzyme inside a bacterial cell?
In the context of bacterial metabolism, what characterizes catabolism?
In the context of bacterial metabolism, what characterizes catabolism?
What enzymes are required for bacteria to break down complex sugars?
What enzymes are required for bacteria to break down complex sugars?
What is the end product of bacterial amino acid breakdown?
What is the end product of bacterial amino acid breakdown?
In bacterial metabolism, what is produced when proteins are broken down by enzymes?
In bacterial metabolism, what is produced when proteins are broken down by enzymes?
What are the key ingredients in Eosin Methylene Blue (EMB) agar that make it both selective and differential?
What are the key ingredients in Eosin Methylene Blue (EMB) agar that make it both selective and differential?
Why is Mannitol Salt Agar (MSA) considered a selective medium?
Why is Mannitol Salt Agar (MSA) considered a selective medium?
On Mannitol Salt Agar (MSA), what does a yellow color around bacterial colonies indicate?
On Mannitol Salt Agar (MSA), what does a yellow color around bacterial colonies indicate?
What does a fuchsia or pink color on Mannitol Salt Agar (MSA) typically indicate?
What does a fuchsia or pink color on Mannitol Salt Agar (MSA) typically indicate?
How does phenol red indicate sugar catabolism?
How does phenol red indicate sugar catabolism?
What does a positive result on Eosin Methylene Blue (EMB) agar for lactose fermentation typically look like?
What does a positive result on Eosin Methylene Blue (EMB) agar for lactose fermentation typically look like?
If an organism produces colorless growth on Eosin Methylene Blue (EMB) agar, what does this indicate?
If an organism produces colorless growth on Eosin Methylene Blue (EMB) agar, what does this indicate?
What is the role of mineral oil in the Oxidation-Fermentation (OF) Glucose test?
What is the role of mineral oil in the Oxidation-Fermentation (OF) Glucose test?
How does bromothymol blue indicate glucose oxidation or fermentation in the OF Glucose test?
How does bromothymol blue indicate glucose oxidation or fermentation in the OF Glucose test?
What does a blue color in the Oxidation-Fermentation (OF) Glucose test typically indicate?
What does a blue color in the Oxidation-Fermentation (OF) Glucose test typically indicate?
In the starch hydrolysis test, what is the purpose of adding iodine to the agar plate after incubation?
In the starch hydrolysis test, what is the purpose of adding iodine to the agar plate after incubation?
In the starch hydrolysis test, what indicates that an organism produces amylase?
In the starch hydrolysis test, what indicates that an organism produces amylase?
What is the purpose of the starch hydrolysis test?
What is the purpose of the starch hydrolysis test?
Which of the following is an ingredient of the starch hydrolysis test?
Which of the following is an ingredient of the starch hydrolysis test?
Which type of organism can grow in the presence or absence of oxygen?
Which type of organism can grow in the presence or absence of oxygen?
Why is it important to use interpretations when analyzing specialized media?
Why is it important to use interpretations when analyzing specialized media?
What term is used to describe an organism that grows weakly in the presence of EMB?
What term is used to describe an organism that grows weakly in the presence of EMB?
Which factor distinguishes oxidation from fermentation?
Which factor distinguishes oxidation from fermentation?
What must be included in the interpretation of a test in specialized media?
What must be included in the interpretation of a test in specialized media?
Flashcards
Metabolism
Metabolism
Chemical processes that occur within living organisms to sustain life.
Catabolism
Catabolism
The breakdown of complex molecules into smaller molecules, releasing energy.
Enzyme
Enzyme
A biological catalyst that speeds up biochemical reactions.
Exoenzymes
Exoenzymes
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Endoenzymes
Endoenzymes
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Selective media
Selective media
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Differential media
Differential media
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Enrichment media
Enrichment media
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Eosin Methylene Blue (EMB)
Eosin Methylene Blue (EMB)
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Mannitol Salt Agar (MSA)
Mannitol Salt Agar (MSA)
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Phenol Red
Phenol Red
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Oxidation
Oxidation
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Fermentation
Fermentation
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Bromothymol Blue
Bromothymol Blue
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Starch Hydrolysis Test
Starch Hydrolysis Test
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Amylase
Amylase
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Study Notes
Introduction to Special Media
- Specialized media is used to enhance growth of some organisms
- Specialized media functions by inhibiting the growth of other organisms
Types of Specialized Media
- Selective media contains chemicals designed to enhance the growth of some organisms while inhibiting others
- Differential media contains ingredients which allow you to distinguish the type of metabolism occurring
- You can identify the type of metabolism by looking for changes in pH indicators, changes from solid to liquid, by-product formation (like a gas bubble), or media clearing
- Enrichment media contains ingredients that enhance the growth of desired bacteria but still allows other bacteria to grow
Eosin Methylene Blue (EMB)
- EMB is a specialized media
- Its ingredients include eosin, methylene blue, agar, lactose, and peptone
- Lactose and peptone are nutrient sources for organisms growing on EMB
- Eosin is not considered a pH indicator
- EMB is a solid media
- EMB is selective for gram-negative bacteria because methylene blue and eosin inhibit gram-positive bacteria
- EMB is differential for lactose fermentation because the media has lactose
Mannitol Salt Agar (MSA)
- MSA is selective for salt tolerance and differential for mannitol fermentation
- Ingredients include sodium chloride, agar, phenol red, mannitol, peptone
- 7.5% salt content makes MSA selective for salt tolerant organisms
- Phenol red makes MSA differential for mannitol fermentation
- MSA is incubated for 24-48 hours
Phenol Red
- With phenol red, if a yellow color is present, carbohydrate was metabolized
- A resultant acid proves sugar catabolism
- Phenol red is yellow at acidic pH
- With phenol red, if a fuchsia or pink color is present, peptone was metabolized
- As a result, ammonia is the end product
- Phenol red presents as pink at a basic pH
- Phenol red is yellow at acidic (low) pH, red at neutral pH, and fuchsia at basic (high) pH
Interpreting EMB Results
- Thick, strong growth indicates the organism is Gram-negative
- Weak growth or no growth indicates the organism is not Gram-negative
- Pink, black, purple, or metallic green growth indicates a positive result for lactose fermentation, using lactose as a nutrient source
- Colorless growth indicates a negative result for lactose fermentation, using peptone as a nutrient source
Interpreting MSA Results
- Growth indicates a salt tolerant organism
- No growth indicates an intolerance to salt
- Yellow color change indicates a positive result for mannitol fermentation
- Fuchsia pink, red, or no color change indicates a negative result for mannitol fermentation
Carbohydrate Catabolism
- Carbohydrate catabolism is necessary to determine an unknown culture
- The 4 Quadrant Streak method used with unknown cultures can allow you to observe the EMB and MSA plates and identify pure or mixed cultures.
Oxidation-Fermentation (OF) Glucose
- Oxidation means glucose or peptone can be oxidized in the presence of oxygen to produce energy for bacteria
- Fermentation does not use or require oxygen, but can take place in the presence of oxygen
- Both oxidation and fermentation of glucose result in acidic end products
- Obligate aerobes only grow in the presence of oxygen
- Facultative anaerobes can grow with or without oxygen
- Obligate anaerobes only grow in the absence of oxygen
OF Glucose Procedure
- OF Glucose uses glucose, bromothymol blue, agar, peptone and bromothymol blue as a pH indicator
- OF Glucose is a differential test for oxidation/fermentation of glucose
- OF Glucose tubes allow oxygen requirement and motility determination
- The test requires two semi-solid deep tubes: one to test aerobic results, and the other anaerobic results
- Semi-solid deeps also allow testing of an organism's motility
Bromothymol Blue
- With bromothymol blue tests, a yellow color means glucose was metabolized
- An acid is the resultant end product
- Bromothymol blue presents as yellow at acidic pH
- With bromothymol blue tests, a blue color means peptone was utilized
- Ammonia is the resultant end product
- Bromothymol blue presents as blue at basic pH
- Using OF Glucose deep tests:
- Anaerobic testing uses mineral oil after inoculating bacteria to test fermentation (no oxygen)
- Aerobic testing does not use mineral oil, testing oxidation and/or fermentation
Starch Hydrolysis Test
- The ingredients of starch hydrolysis tests are starch, beef extract (peptone), and agar
- The purpose of the test is to determine whether an organism produces exoenzyme amylase to hydrolyze starch
- Microbes can produce the exoenzyme amylase to use starch
- The basic formula is:
- Starch yields glucose yields acid catalyzed by exoenzyme and endoenzyme
- Iodine detects the presence or absence of starch in bacterial growth
- Iodine reacts with starch and produces a blue, black, or dark brown color
Determining Amylase Production
- Starch causes iodine to appear dark in color
- Glucose does not cause iodine to appear dark in color
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