Textbook Question
Thermal death point is not considered an accurate measure of the effectiveness of heat sterilization. List three factors that can alter thermal death point.
1
views
Ch. 7 - The Control of Microbial Growth
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398
Not the one you use?Change textbookSelect a different textbook
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 4
The antimicrobial effect of gamma radiation is due to:(a) ________.
The antimicrobial effect of ultraviolet radiation is due to: (b) ________.
Verified step by step guidance1
Step 1: Understand that gamma radiation and ultraviolet (UV) radiation have different mechanisms by which they exert antimicrobial effects.
Step 2: Recall that gamma radiation is a form of ionizing radiation, which means it has enough energy to remove tightly bound electrons from atoms, creating ions. This ionization leads to damage in microbial DNA and other cellular components.
Step 3: Therefore, the antimicrobial effect of gamma radiation is primarily due to the ionization and generation of free radicals that cause breaks in DNA strands and damage to cellular molecules.
Step 4: On the other hand, ultraviolet radiation is non-ionizing and does not cause ionization but instead causes specific damage to DNA by inducing the formation of thymine dimers, which are covalent linkages between adjacent thymine bases in DNA.
Step 5: These thymine dimers distort the DNA structure, interfering with replication and transcription, ultimately leading to microbial death or inability to reproduce.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
2mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Mechanism of Gamma Radiation on Microorganisms
Gamma radiation kills microbes primarily by causing ionization that leads to the formation of free radicals. These free radicals damage critical cellular components such as DNA, proteins, and membranes, resulting in cell death or loss of reproductive ability.
Recommended video:
Guided course
01:25
Importance of Microorganisms
Mechanism of Ultraviolet (UV) Radiation on Microorganisms
Ultraviolet radiation exerts its antimicrobial effect mainly by inducing DNA damage, specifically forming thymine dimers. These dimers disrupt DNA replication and transcription, preventing microbial growth and leading to cell death.
Recommended video:
Guided course
03:31Nucleotide Excision Repair
Differences Between Ionizing and Non-Ionizing Radiation
Gamma radiation is ionizing, meaning it has enough energy to remove tightly bound electrons, causing direct and indirect damage to cellular molecules. UV radiation is non-ionizing and primarily causes damage through chemical changes like DNA dimer formation rather than ionization.
Recommended video:
Guided course
06:18Irradiation
Related Practice
Textbook Question
Which of the following is used to control microbial growth in foods?
a. Organic acids
b. Alcohols
c. Aldehydes
d. Heavy metals
e. All of the above
1
views
Textbook Question
A bacterial culture was in log phase in the following figure. At time x, an antibacterial compound was added to the culture. Draw the lines indicating the addition of a bactericidal compound and a bacteriostatic compound. Explain why the viable count does not immediately drop to zero at x.
2
views
Textbook Question
Use the following information to answer questions 6 and 7. The data were obtained from a use-dilution test comparing four disinfectants against Salmonella Choleraesuis.
G = growth, NG = no growth
Which disinfectant is the most effective?
5
views
Textbook Question
Which of these disinfectants does not act by disrupting the plasma membrane?
a. Phenolics
b. Phenol
c. Quats
d. Halogens
e. Biguanides
2
views
Textbook Question
Which of the following cannot be used to sterilize a heat-labile solution stored in a plastic container?
a. Gamma radiation
b. Ethylene oxide
c. Supercritical fluids
d. Autoclaving
e. Short-wavelength radiation