Ch. 7 - The Control of Microbial Growth

Tortora - Microbiology: An Introduction 14th Edition

Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook

Tortora 14th Edition

Ch. 7 - The Control of Microbial Growth

Problem 4

Chapter 7, Problem 4

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

Verified step by step guidance

Step 1: Understand the term 'heat-labile' which refers to substances that are sensitive to heat and can be denatured or destroyed by high temperatures.

Step 2: Review each sterilization method listed and consider whether it involves high heat that could damage a heat-labile solution or the plastic container.

Step 3: Gamma radiation (a), ethylene oxide (b), supercritical fluids (c), and short-wavelength radiation (e) are sterilization methods that do not rely on high temperatures and are generally safe for heat-sensitive materials.

Step 4: Autoclaving (d) uses high-pressure saturated steam at temperatures around 121°C, which is a high-heat process and can damage heat-labile solutions and plastic containers.

Step 5: Conclude that autoclaving is the sterilization method that cannot be used for heat-labile solutions stored in plastic containers due to its high temperature.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Heat-labile Solutions

Heat-labile solutions are sensitive to high temperatures and can be damaged or denatured when exposed to heat. Understanding this is crucial because sterilization methods involving heat, such as autoclaving, are unsuitable for these solutions to prevent degradation of their components.

Sterilization Methods and Their Mechanisms

Sterilization methods vary in their approach: autoclaving uses moist heat under pressure, gamma radiation and short-wavelength radiation use ionizing and non-ionizing radiation respectively, ethylene oxide is a chemical sterilant, and supercritical fluids use unique solvent properties. Knowing how each method works helps determine their compatibility with different materials.

Material Compatibility in Sterilization

The container material, such as plastic, affects which sterilization methods can be used without damage. Some methods, like autoclaving, may deform plastics due to heat, while others like ethylene oxide or radiation can sterilize without compromising container integrity. This concept is key to selecting appropriate sterilization techniques.

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Related Practice

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.

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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

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Textbook Question

The antimicrobial effect of gamma radiation is due to:(a) ________.

The antimicrobial effect of ultraviolet radiation is due to: (b) ________.

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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.

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Textbook Question

Which of the following is most effective for sterilizing mattresses and plastic Petri dishes?

a. Chlorine

b. Ethylene oxide

c. Glutaraldehyde

d. Autoclaving

e. Nonionizing radiation

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Textbook Question

Which of these disinfectants does not act by disrupting the plasma membrane?

a. Phenolics