Textbook Question
Place the following in the order in which they are found in a host cell: (1) capsid proteins;
(2) infective phage particles; (3) phage nucleic acid.
a. 1, 2, 3
b. 3, 2, 1
c. 2, 1,3
d. 3, 1, 2
e. 1, 3, 2
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Ch. 13 - Viruses, Viroids, and Prions
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 13, Problem 7
Recall from Chapter 1 that Koch's postulates are used to determine the etiology of a
disease. Why is it difficult to determine the etiology of
a. a viral infection, such as influenza?
b. cancer?
Verified step by step guidance1
Step 1: Understand Koch's postulates, which are a set of criteria used to establish a causative relationship between a microbe and a disease. These include isolating the microorganism from a diseased organism, growing it in pure culture, causing the disease in a healthy organism by introducing the cultured microbe, and then re-isolating the same microbe from the newly diseased host.
Step 2: For part (a), consider why viral infections like influenza pose challenges to Koch's postulates. Viruses require host cells to replicate and cannot be grown in pure culture on standard media, which violates one of Koch's key criteria.
Step 3: Also for part (a), recognize that some viruses may cause disease only under certain conditions or in specific hosts, and asymptomatic carriers can harbor the virus without showing disease, complicating the direct cause-effect relationship.
Step 4: For part (b), analyze why cancer is difficult to attribute to a single causative agent using Koch's postulates. Cancer is a complex, multifactorial disease involving genetic mutations, environmental factors, and sometimes infectious agents, making it hard to isolate a single pathogen responsible for the disease.
Step 5: Additionally for part (b), note that cancer cells are derived from the host's own cells and are not infectious microorganisms, so the criteria of isolating and reintroducing a pathogen to cause disease do not apply in the same way as for infectious diseases.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Koch's Postulates
Koch's postulates are a set of criteria used to establish a causative relationship between a microbe and a disease. They require isolating the pathogen from a diseased host, growing it in pure culture, reproducing the disease in a healthy host, and re-isolating the same pathogen. These steps help confirm the etiology of infectious diseases.
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01:36
Koch's Postulates
Challenges in Applying Koch's Postulates to Viral Infections
Viruses cannot be grown in pure culture without host cells, making it difficult to fulfill Koch's postulates. Additionally, viral infections like influenza can vary in symptoms and severity, and some viruses may be present without causing disease, complicating the direct link between virus and illness.
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03:31The 4 Koch's Postulates
Complex Etiology of Cancer
Cancer is caused by multiple factors including genetic mutations, environmental influences, and sometimes infectious agents, making it a multifactorial disease. Unlike infectious diseases, cancer does not result from a single pathogen, so Koch's postulates cannot be directly applied to determine its cause.
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02:59Complex Media
Related Practice
Textbook Question
The ability of a virus to infect an organism is regulated by
a. the host species.
b. the type of cells.
c. the availability of an attachment site.
d. cell factors necessary for viral replication.
e. all of the above
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Textbook Question
An example of lysogeny in animals could be
a. slow viral infections.
b. latent viral infections.
c. T-even bacteriophages.
d. infections resulting in cell death.
e. none of the above
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Textbook Question
Persistent viral infections such as (a) ________ might be caused by (b) ________ that are (c) ________.
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Textbook Question
Which of the following statements is false?
a. Viruses contain DNA or RNA.
b. The nucleic acid of a virus is surrounded by a protein coat.
c. Viruses multiply inside living cells using viral mRNA, tRNA, and ribosomes.
d. Viruses cause the synthesis of specialized infectious elements.
e. Viruses multiply inside living cells.
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Textbook Question
Some antibiotics activate phage genes. MRSA releasing Panton-Valentine leukocidin is a toxin that can cause a life-threatening disease. Why can such a disease develop following antibiotic treatment?
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