Domanda del libro di testo
What is the purpose of a counterstain in the acid-fast stain?
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Ch. 3 - Observing Microorganisms Through a Microscope
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398
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TOC.tableOfContents
- Ch. 1 - The Microbial World and You18
- Ch. 2 - Chemical Principles20
- Ch. 3 - Observing Microorganisms Through a Microscope18
- Ch. 7 - The Control of Microbial Growth20
- Ch. 9 - Biotechnology & DNA Technology20
- Ch. 10 - Classification of Microorganisms15
- Ch. 11 - The Prokaryotes: Domains Bacteria and Archaea14
- Ch. 12 - The Eukaryotes: Fungi, Algae, Protozoa, and Helminths17
- Ch. 13 - Viruses, Viroids, and Prions20
- Ch. 14 - Principles of Disease and Epidemiology21
- Ch. 15 - Microbial Mechanisms of Pathogenicity19
- Ch. 16 - Innate Immunity: Nonspecific Defenses of the Host20
- Ch. 17 - Adaptive Immunity: Specific Defenses of the Host20
- Ch. 18 - Practical Applications of Immunology20
- Ch. 19 - Disorders Associated with the Immune System19
- Ch. 20 - Antimicrobial Drugs19
- Ch. 21 - Microbial Diseases of the Skin and Eyes21
- Ch. 22 - Microbial Diseases of the Nervous System19
- Ch. 23 - Microbial Diseases of the Cardiovascular and Lymphatic Systems20
- Ch. 24 - Microbial Diseases of the Respiratory System20
- Ch. 25 - Microbial Diseases of the Digestive System20
- Ch. 26 - Microbial Diseases of the Urinary and Reproductive Systems19
- Ch. 27 - Environmental Microbiology20
- Ch. 28 - Applied and Industrial Microbiology19
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Tortora 14th EditionCh. 3 - Observing Microorganisms Through a MicroscopeProblema 6
Tortora 14th EditionCh. 3 - Observing Microorganisms Through a MicroscopeProblema 6Capitolo 3, Problema 6
Why is a mordant used in the Gram stain? In the flagella stain?
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Understand that a mordant is a substance used in staining procedures to enhance the binding of the primary stain to the target structure, making it more visible under the microscope.
In the Gram stain, the mordant (usually iodine) forms a complex with the primary stain (crystal violet), creating a larger molecule that gets trapped within the thick peptidoglycan layer of Gram-positive bacterial cell walls.
This complex helps differentiate Gram-positive bacteria (which retain the crystal violet-iodine complex and appear purple) from Gram-negative bacteria (which do not retain it and are counterstained later).
In the flagella stain, the mordant is used to coat the thin flagella with a substance that increases their diameter, making them thick enough to be seen under a light microscope after staining.
Thus, in both stains, the mordant's role is to improve the visibility and differentiation of specific bacterial structures by enhancing stain retention or increasing structural size.
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Gram Stain Procedure
The Gram stain is a differential staining technique used to classify bacteria into Gram-positive or Gram-negative based on their cell wall structure. It involves applying a primary stain, a mordant, a decolorizer, and a counterstain to distinguish bacterial types by color.
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Gram Stain
Role of Mordant in Staining
A mordant is a chemical agent that binds to a dye and fixes it onto or into a specimen, enhancing the stain's intensity and retention. In the Gram stain, iodine acts as a mordant, forming a complex with crystal violet that gets trapped in thick peptidoglycan layers of Gram-positive bacteria.
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04:57Gram Stain
Flagella Stain and Mordant Use
Flagella are thin structures that are difficult to see under a microscope, so a mordant is used in flagella staining to coat and thicken the flagella, making them visible. The mordant binds to the stain and flagella, increasing their diameter for easier observation.
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04:57Gram Stain
Pratica correlata
Domanda del libro di testo
Which of the following pairs is mismatched?
a. Capsule—negative stain
b. Cell arrangement—simple stain
c. Cell size—negative stain
d. Gram stain—bacterial identification
e. None of the above
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Domanda del libro di testo
The maximum magnification of a compound microscope is (a) ________; that of an electron microscope, (b) ________. The maximum resolution of a compound microscope is (c) ________; that of an electron microscope, (d) ________. One advantage of a scanning electron microscope over a transmission electron microscope is (e) ________.
1905
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Domanda del libro di testo
Which of the following is not a functionally analogous pair of stains?
a. Nigrosin and malachite green
b. Crystal violet and carbolfuchsin
c. Safranin and methylene blue
d. Ethanol-acetone and acid-alcohol
e. All of the above pairs are functionally analogous.
1454
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Domanda del libro di testo
Assume you stain Clostridium by applying a basic stain, carbolfuchsin, with heat, decolorizing with acid-alcohol, and counterstaining with an acidic stain, nigrosin. Through the microscope, the endospores are 1, and the cells are stained 2.
a. 1—red; 2—black
b. 1—black; 2—colorless
c. 1—colorless; 2—black
d. 1—red; 2—colorless
e. 1—black; 2—red
1649
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Domanda del libro di testo
Calculate the total magnification of the nucleus of a cell being observed through a compound light microscope with a 10x ocular lens and an oil immersion lens.
1828
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