Q: A batch culture of bacteria is started with $$10^3$$ cells. After 6 generations, how many cells will be present? Use the formula $$N = N_0$ \times 2^n.$$

$$N = 10^3$ \times 2^6$ = 10^3$ \times 64 = 6.4 \times 10^4$

Question 1

Which of the following best describes a differential culture medium?

Accepted Answer

A medium that contains nutrients for the growth of all microorganisms but allows differentiation based on metabolic properties.

Question 2

A batch culture of bacteria is started with $$10^3$$ cells. After 6 generations, how many cells will be present? Use the formula $$N = N_0$ 	imes 2^n.$$

Accepted Answer

$$N = 10^3$ 	imes 2^6$ = 10^3$ 	imes 64 = 6.4 	imes 10^4$

Question 3

Which of the following is NOT a method for measuring microbial growth?

Accepted Answer

Gram staining

Question 4

Which phase of the bacterial growth curve is characterized by active cell division and exponential increase in cell number?

Accepted Answer

Log (exponential) phase

Question 5

A microbiologist wants to grow strict anaerobes. Which method would be most appropriate?

Accepted Answer

Using an anaerobic jar with a gas-generating packet to remove oxygen

Question 6

Which enzyme protects aerobic bacteria from the toxic effects of hydrogen peroxide ($$H_2O_2$$)?

Accepted Answer

Catalase

Question 7

Psychrophiles are adapted to grow at low temperatures. Which molecular adaptation is most important for their survival?

Accepted Answer

Increased proportion of unsaturated fatty acids in their membrane lipids

Question 8

Which of the following statements about autoclaves is correct?

Accepted Answer

Autoclaves sterilize by using pressurized steam at 121°C for a specified time.

Question 9

Which antimicrobial agent acts primarily by inhibiting protein synthesis at the 30S ribosomal subunit?

Accepted Answer

Aminoglycosides

Question 10

Which term describes microorganisms that require high salt concentrations for growth?

Accepted Answer

Halophiles

Question 11

A chemostat is used in continuous culture. What is its primary function?

Accepted Answer

Maintaining a constant environment by continuously adding fresh medium and removing culture at a fixed rate

Question 12

Which of the following forms of oxygen is most toxic to anaerobic bacteria?

Accepted Answer

Superoxide anion ($$O_2$$^-$$)

Question 13

Which of the following best describes the action of beta-lactam antibiotics?

Accepted Answer

Inhibition of cell wall synthesis by blocking peptidoglycan cross-linking

Question 14

Which term refers to the lowest concentration of an antimicrobial agent that prevents visible growth of a microorganism?

Accepted Answer

Minimal inhibitory concentration (MIC)

Question 15

Which of the following is a real-life application of lyophilization in microbiology?

Accepted Answer

Preservation of bacterial cultures by freeze-drying for long-term storage

Question 16

Which environmental factor is most critical for the growth of xerophiles?

Accepted Answer

Low water activity ($$A_w)$$

Question 17

Which of the following is a function of superoxide dismutase in bacteria?

Accepted Answer

Conversion of superoxide anion ($$O_2$$^-$$) to hydrogen peroxide (H_2O_2$)

Question 18

Which term describes bacteria that grow optimally at pH values above 8?

Accepted Answer

Alkalinophiles

Question 19

Taq polymerase is significant in molecular biology because:

Accepted Answer

It is thermostable and can withstand the high temperatures used in PCR.

Question 20

Which antimicrobial agent acts by denaturing proteins and disrupting cell membranes, and is commonly used as a disinfectant in hospitals?

Accepted Answer

Phenols

Culture, Growth, and Control of Microorganisms

Guida di studio - Domande di pratica

Study guide - Flashcard