Question 1

Which of the following best describes a chemoautotroph?

Accepted Answer

Uses inorganic carbon sources and chemical compounds as an energy source

Question 2

A bacterial culture is grown in a broth tube. After incubation, growth is observed only at the bottom of the tube. Which type of organism is most likely present?

Accepted Answer

Obligate anaerobe

Question 3

Why can oxygen be fatal to obligate anaerobes?

Accepted Answer

They lack enzymes such as superoxide dismutase and catalase to detoxify reactive oxygen species

Question 4

Which enzyme is responsible for converting hydrogen peroxide ($\mathrm{H_2O_2}$) into water and oxygen?

Accepted Answer

Catalase

Question 5

Nitrogen fixation is important in microbiology because:

Accepted Answer

It converts atmospheric nitrogen ($\mathrm{N_2}$) into ammonia ($\mathrm{NH_3}$), which can be used by living organisms

Question 6

A microorganism that grows optimally at temperatures between $0^\circ \mathrm{C}$ and $15^\circ \mathrm{C}$ is called a:

Accepted Answer

Psychrophile

Question 7

Which of the following best describes an acidophile?

Accepted Answer

A microorganism that grows best at low pH

Question 8

Halophiles are microorganisms that:

Accepted Answer

Require high concentrations of salt for growth

Question 9

Which of the following is a major impact of biofilms in human health?

Accepted Answer

Biofilms increase antibiotic resistance in infections

Question 10

Quorum sensing in bacteria is best described as:

Accepted Answer

A process where bacteria communicate using chemical signals to coordinate group behaviors such as biofilm formation

Question 11

A pure culture is defined as:

Accepted Answer

A culture containing only one species of microorganism

Question 12

CFU stands for:

Accepted Answer

Colony Forming Unit

Question 13

Which type of media would you use to distinguish between two bacterial species based on their ability to ferment lactose?

Accepted Answer

Differential media

Question 14

Binary fission in bacteria is best described as:

Accepted Answer

A process where a single cell divides into two identical daughter cells

Question 15

If a bacterial population doubles every 30 minutes, how many cells will there be after 2 hours if you start with 100 cells? Use the formula $N = N_0 	imes 2^n$, where $n$ is the number of generations.

Accepted Answer

1600

Question 16

During which phase of the bacterial growth curve are cells most susceptible to antibiotics targeting cell wall synthesis?

Accepted Answer

Log (exponential) phase

Question 17

Serial dilution and viable plate counts are used to:

Accepted Answer

Estimate the number of living bacteria in a sample

Question 18

A sample is diluted 1:100, and 0.1 mL is plated. After incubation, 50 colonies are counted. What is the original concentration of bacteria in the sample (CFU/mL)?

Accepted Answer

$5 	imes 10^5$

Question 19

Which of the following best describes a selective medium?

Accepted Answer

A medium that inhibits the growth of some organisms while allowing others to grow

Question 20

A patient develops a chronic infection on a catheter. Which microbial process is most likely responsible for the persistence of the infection?

Accepted Answer

Biofilm formation

Microbial Nutrition and Growth: Step-by-Step Study Guidance

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