Textbook Question
What bacteria have porins, are resistant to bisphenols, and survive and may grow in quats?
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Ch. 7 - The Control of Microbial Growth
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398
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Table of contents
- Ch. 1 - The Microbial World and You18
- Ch. 2 - Chemical Principles20
- Ch. 3 - Observing Microorganisms Through a Microscope18
- Ch. 4 - Functional Anatomy of Prokaryotic and Eukaryotic Cells21
- Ch. 5 - Microbial Metabolism20
- Ch. 6 - Microbial Growth20
- Ch. 7 - The Control of Microbial Growth20
- Ch. 8 - Microbial Genetics19
- 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
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook
Chapter 7, Problem 9
You and your classmates are trying to determine how a disinfectant might kill cells. You observe that when you spill the disinfectant in a tube of reduced litmus milk, the litmus turns blue again. You suggest to your classmates that:
a. The disinfectant might inhibit cell wall synthesis
b. The disinfectant might oxidize molecules
c. The disinfectant might inhibit protein synthesis
d. The disinfectant might denature proteins
e. The disinfectant might damage DNA
Verified step by step guidance1
Step 1: Understand the role of litmus milk in microbiology. Litmus milk contains litmus, a pH indicator that changes color depending on the chemical environment, and milk proteins that can be metabolized by bacteria.
Step 2: Recognize that reduced litmus milk appears white or colorless because the litmus indicator is in a reduced (electron-rich) state, often due to bacterial metabolic activity under anaerobic conditions.
Step 3: Observe that when the disinfectant is added, the litmus turns blue again, indicating that the environment has become oxidized (electron-poor), reversing the reduction of the litmus indicator.
Step 4: Connect the color change to the chemical action of the disinfectant. Since the litmus turns blue (oxidized), the disinfectant likely causes oxidation of molecules in the medium.
Step 5: Conclude that among the options, the disinfectant's effect is best explained by its ability to oxidize molecules, which corresponds to option (b).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Redox Reactions and Litmus Indicator
Litmus milk contains litmus, a pH and redox indicator that changes color based on oxidation-reduction reactions. Reduced litmus appears white or colorless, while oxidized litmus is blue or purple. Observing litmus turning blue indicates oxidation, meaning the disinfectant likely acts as an oxidizing agent.
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Mechanisms of Disinfectant Action
Disinfectants kill microbes through various mechanisms such as inhibiting cell wall synthesis, denaturing proteins, damaging DNA, or oxidizing cellular components. Understanding these mechanisms helps identify how a disinfectant affects microbial cells and which cellular targets are involved.
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Protein Denaturation vs. Oxidation
Protein denaturation involves disrupting protein structure without necessarily changing redox states, while oxidation chemically alters molecules by removing electrons. Since litmus color change indicates oxidation, the disinfectant likely oxidizes molecules rather than just denaturing proteins.
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Related Practice
Textbook Question
A large hospital washes burn patients in a stainless steel tub. After each patient, the tub is cleaned with a quat. It was noticed that 14 of 20 burn patients acquired Pseudomonas infections after being bathed. Provide an explanation for this high rate of infection.
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Textbook Question
Which of the following is not a characteristic of quaternary ammonium compounds?
a. Bactericidal against gram-positive bacteria
b. Sporicidal
c. Amebicidal
d. Fungicidal
e. Kills enveloped viruses
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Textbook Question
The use-dilution values for two disinfectants tested under the same conditions are as follows:
Disinfectant A—1:2
Disinfectant B—1:10,000.
If both disinfectants are designed for the same purpose, which would you select?
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Textbook Question
Which of the following is most likely to be bactericidal?
a. Membrane filtration
b. Ionizing radiation
c. Lyophilization (freeze-drying)
d. Deep-freezing
e. All of the above
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