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 10

Chapter 7, Problem 10

What bacteria have porins, are resistant to bisphenols, and survive and may grow in quats?

Verified step by step guidance

Step 1: Understand the role of porins in bacteria. Porins are protein channels located in the outer membrane of Gram-negative bacteria, allowing the passage of small molecules. This structural feature is key to identifying the type of bacteria in question.

Step 2: Recognize that bisphenols, such as triclosan, target bacterial membranes and enzymes, but some bacteria show resistance due to their outer membrane properties and efflux mechanisms.

Step 3: Note that quaternary ammonium compounds (quats) are disinfectants that disrupt membranes, but certain bacteria can survive or even grow in their presence due to intrinsic resistance mechanisms.

Step 4: Combine these characteristics: bacteria with porins (indicating Gram-negative), resistance to bisphenols, and ability to survive or grow in quats are typically Gram-negative bacteria with robust outer membranes and efflux pumps.

Step 5: Conclude that the bacteria fitting this description are Gram-negative bacteria, such as Pseudomonas species, which are known for their porins, resistance to bisphenols, and survival in quats.

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Key Concepts

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

Porins in Bacteria

Porins are protein channels located in the outer membrane of Gram-negative bacteria that allow the passive diffusion of small molecules. They play a crucial role in controlling the entry of substances, including antibiotics and disinfectants, influencing bacterial resistance.

Resistance to Bisphenols

Bisphenols, such as triclosan, are antimicrobial agents targeting bacterial membranes and enzymes. Some bacteria develop resistance through mechanisms like efflux pumps or membrane modifications, enabling them to survive despite bisphenol exposure.

Survival and Growth in Quaternary Ammonium Compounds (Quats)

Quats are disinfectants that disrupt microbial membranes. Certain bacteria, especially some Gram-negative species, can resist or tolerate quats by altering membrane permeability or producing protective biofilms, allowing them to survive and sometimes grow in their presence.

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Related Practice

Textbook Question

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

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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 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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