Question 1

Which of the following best describes a mesophile?

Accepted Answer

A microorganism that grows optimally at temperatures around $$39^\circ C$$

Question 2

A bacterial culture starts with $$1.0 	imes 10^6$ cells/mL. After 5 hours, the concentration is 2.0$$ 	imes $$10^8$$ cells/mL. How many generations ($$n) $$have occurred? Use the formula $$n = 3.3 (\log N_t - \log N_0$).$$

Accepted Answer

$$n = 6.6$$

Question 3

Which of the following is a disadvantage of using optical density to measure microbial growth?

Accepted Answer

It cannot distinguish between live and dead cells

Question 4

Which protein is crucial for the formation of the Z ring during bacterial cell division?

Accepted Answer

FtsZ

Question 5

A bacterium has a generation time of 30 minutes. If you inoculate a culture with $$1.0 	imes 10^6$ cells, how long (in hours) will it take to reach 1.0$$ 	imes $$10^{12}$$ cells? Use $$n = 3.3 (\log N_t - \log N_0$)$$ and total time $$= n 	imes$$ generation time.

Accepted Answer

18 hours

Question 6

Which of the following best explains why most bacteria are classified as neutrophiles?

Accepted Answer

They grow optimally at pH values near 7

Question 7

What would happen to an E. coli cell if the MinC, MinD, and MinE genes were deleted?

Accepted Answer

The cell would divide at random locations, leading to minicell formation

Question 8

Which of the following is a characteristic of biofilms that makes them difficult to treat with antibiotics?

Accepted Answer

Cells in biofilms are enmeshed in a polysaccharide matrix

Question 9

Which Streptococcus species is commonly used in the production of yogurt?

Accepted Answer

Streptococcus thermophilus

Question 10

Which of the following is a toxic byproduct of oxygen metabolism in bacteria?

Accepted Answer

Superoxide anion $$O_2$$^-$$

Question 11

Which type of medium contains precisely known amounts of all components?

Accepted Answer

Defined medium

Question 12

Which phase of microbial growth is characterized by rapid cell division and exponential increase in cell number?

Accepted Answer

Log phase

Question 13

Which of the following is a major reason for the increase in pertussis cases in recent decades?

Accepted Answer

Decreased herd immunity and waning vaccine effectiveness

Question 14

Which enzyme is responsible for neutralizing hydrogen peroxide ($$H_2O_2) in $$aerobic bacteria?

Accepted Answer

Catalase

Question 15

Which of the following best describes the role of DnaA in bacterial DNA replication?

Accepted Answer

It binds to the origin of replication and initiates DNA strand separation

Question 16

A culture of bacteria is diluted $$1:10$$ three times, $$1:100$$ three times, and $$1:5$$ once. If you plate $$0.2 mL $$and count $$50$$ colonies, what was the original concentration of the culture? Use $$C = \frac{	ext{colonies}}{	ext{volume plated} 	imes 	ext{total dilution factor}}.$$

Accepted Answer

$$6.25 	imes 10^6$ cells/mL

Question 17

Which of the following is true about hyperthermophiles?

Accepted Answer

They have optimum growth temperatures above $$80^\circ C$$

Question 18

Which of the following is a real-world application of lactic acid bacteria?

Accepted Answer

Fermentation of pickles and cheese

Question 19

Which protein hydrolyzes GTP to provide energy for cell division in bacteria?

Accepted Answer

FtsZ

Question 20

Which of the following best explains why biofilms are a concern in medical settings?

Accepted Answer

They protect bacteria from antibiotics and immune responses

Microbial Growth I & II: Factors, Measurement, and Clinical Relevance

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