Microbial Growth and Carrying Capacity

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What is the primary mechanism of action of certain microbial control agents on the plasma membrane?

Facilitating the formation of hydrogen bonds
Altering its permeability due to damage to lipid and protein components (correct)
Forming covalent bonds with proteins
Increasing the membrane potential

What is the main difference between antimicrobial and antibacterial compounds?

Antimicrobial compounds are less effective against fungi
Antimicrobial compounds are more effective against viruses
Antimicrobial compounds are only effective against endospores
Antimicrobial compounds are effective against all types of microorganisms, while antibacterial compounds are only effective against bacteria (correct)

What is the purpose of commercial sterilization in canned food?

To kill vegetative pathogens
To promote the growth of beneficial microorganisms
To kill endospores of Clostridium botulinum (correct)
To remove prions from the food

What is the effect of Triclosan on microbial populations?

It gives rise to antimicrobial resistance indirectly (C) Signup and view all the answers

What is the primary goal of degerming?

To remove microbes from a limited area, such as the skin around an injection site (B) Signup and view all the answers

What is the effect of certain microbial control agents on cellular proteins?

They damage cellular proteins by breaking hydrogen bonds and covalent bonds (D) Signup and view all the answers

What is the primary mechanism by which moist heat kills microorganisms?

Denaturation of enzymes (C) Signup and view all the answers

What is the term used to describe the lowest temperature at which all microorganisms in a liquid culture are killed in 10 minutes?

Thermal death point (C) Signup and view all the answers

What is the primary advantage of autoclaving over boiling for sterilization?

It is more effective against bacterial spores (D) Signup and view all the answers

What is the purpose of the HTST method of pasteurization?

To destroy pathogens without altering the flavor of the food (D) Signup and view all the answers

What is the term used to describe the absence of significant contamination?

Asepsis (A) Signup and view all the answers

What is the term used to describe the length of time required to kill all bacteria in a liquid culture at a given temperature?

Thermal death time (C) Signup and view all the answers

What is the primary effect of ionizing radiation on water?

Formation of highly reactive hydroxyl radicals (A) Signup and view all the answers

What is the wavelength of UV radiation that is most effective for germicidal purposes?

260 nm (B) Signup and view all the answers

How do microwaves kill microbes?

Indirectly, as materials get hot (A) Signup and view all the answers

What is the effect of refrigeration on microbial growth?

Bacteriostatic (A) Signup and view all the answers

What is the purpose of lyophilization?

To preserve microbial cultures, food, and drugs (D) Signup and view all the answers

What is the characteristic of chlorine as a disinfectant?

Effective against all the test bacteria but more effective against gram-positive (C) Signup and view all the answers

What is the primary factor that limits the growth of bacteria in an environment?

Available nutrients (C) Signup and view all the answers

During which phase of the microbial growth curve do bacteria prepare for binary fission?

Lag phase (B) Signup and view all the answers

What is the result when the number of bacterial cells produced is equal to the number of cells that die?

Stationary phase (B) Signup and view all the answers

What is the purpose of adding 20% glycerol to an agar slant?

To preserve the bacteria for up to 6 years (C) Signup and view all the answers

What is the definition of generation time in microbiology?

The time it takes for a bacterial cell to divide or double in number (C) Signup and view all the answers

What is the relationship between the number of bacterial cells produced and the number of cells that die when a population exceeds the carrying capacity?

The number of cells produced is equal to the number of cells that die (D) Signup and view all the answers

Which of the following factors should be considered when selecting a disinfectant?

Presence of organic matter and temperature (C) Signup and view all the answers

What is the primary purpose of the use-dilution test?

To evaluate the bacterial survival in a manufacturer's recommended dilution (D) Signup and view all the answers

Which of the following acids is used as a food preservative to inhibit fungal metabolism?

Sorbic acid (D) Signup and view all the answers

What is the mechanism of action of aldehydes, such as formaldehyde and glutaraldehyde, as chemical disinfectants?

Denaturation of proteins (B) Signup and view all the answers

What is the primary mechanism of action of ethylene oxide as a sterilizing agent?

Protein denaturation (A) Signup and view all the answers

Which of the following methods is used to evaluate the effectiveness of agents against viruses, endospore-forming bacteria, mycobacteria, and fungi?

Use-dilution test (B) Signup and view all the answers