Microbial Growth Test Bank Answers Chapter 9

Chapter 9: Microbial Growth

= Correct answer

Multiple Choice

1. Bacteria most commonly reproduce using which of the following methods?

A. binary fission

B. budding

C. meiosis

D. mitosis

Difficulty: Easy

ASM Standard: N/A

1. Which structure separates new daughter cells in binary fission?
2. the crescent

B. the division septum

C. the FtsZ

D. the spindle apparatus

Difficulty: Easy

ASM Standard: N/A

1. Which of the following is another term for generation time?

A. doubling time

B. growth rate

C. mitotic index

D. replication index

Difficulty: Easy

ASM Standard: N/A

1. Which of the following best describes culture density?

A. another term for a batch culture

B. the number of cells per unit volume

C. the reproducible pattern of growth

D. the total number of cells

Difficulty: Easy

ASM Standard: 36

1. Which of the following is the correct order of phases of growth in the growth curve of a batch culture?

A.

B.

C.

D.

Difficulty: Easy

ASM Standard: 36

1. Which of the following is not a common way bacteria divide?

A. binary fission

B. budding

C. fragmentation

D. sporulation

Difficulty: Moderate

ASM Standard: N/A

1. Which of the following is the term for free-living bacteria?

A. biofilms

B. pathogenic

C. planktonic

D. sessile

Difficulty: Easy

ASM Standard: 21

1. Which of the following is not a reactive oxygen species?

A. atmospheric oxygen

B. peroxides

C. singlet oxygen

D. superoxide

Difficulty: Easy

ASM Standard: 14

1. Which of the following best describes FtsZ?

A. a cytoskeletal protein in eukaryotic cells

B. the protein that assembles the Z ring, which forms a divisome before division by binary fission

C. the protein that forms within the central structure of the new cell wall and septum that separates the daughter cells during binary fission

D. the protein that gives structure to spirochetes, contributing to their unusual shape and motility

Difficulty: Moderate

ASM Standard: N/A

1. Which microbial pathogen has an unusually long doubling time?

A. Bacillus subtilis

B. Escherichia coli

C. Mycobacterium leprae

D. Salmonella typhimurium

Difficulty: Moderate

ASM Standard: N/A

1. The initial cells added to a batch culture are called which of the following?
2. the batch
3. the culture
4. the inoculum
5. the lagging cells

Difficulty: Moderate

ASM Standard: 36

1. Which best describes bacterial growth during the log phase of the growth curve?

A. exponential

B. linear

C. S-shaped

D. stationary

Difficulty: Moderate

ASM Standard: N/A

1. Which best defines the term “persisters?”

A. cells that form endospores rapidly when environmental conditions become unfavorable, allowing them to survive in a dormant state without causing disease symptoms

B. cells that persist in the log phase for much longer than other cells

C. cells that rapidly colonize new environments by releasing virulence factors and moving through tissues, allowing them to contribute to severe systemic infections.

D. cells with relatively slow metabolic rates that survive longer than others during the death phase and that can cause chronic infections

Difficulty: Moderate

ASM Standard: 14, 23

1. Which type of system is used to maintain bacteria in a relatively constant environment, allowing them to stay in the log phase of growth?

A. bacteriostat

B. chemostat

C. maintenance state

D. stable state

Difficulty: Moderate

ASM Standard: 36

1. Which of the following is an indirect method of measuring numbers of bacterial cells?

A. a Coulter counter

B. a Petroff-Hausser chamber

C. microscopic cell count

D. turbidity measurements

Difficulty: Moderate

ASM Standard: 35, 36

1. Which of the following is not a common step in preparing a pour plate to make a count of microbial numbers?

A. A serial dilution is performed.

B. Bacteria are spread across the agar, using a sterile spreader.

C. Bacteria are mixed with warm agar and poured onto a Petri plate, then swirled.

D. The sample is allowed to grow, then colonies are counted.

Difficulty: Moderate

ASM Standard: 33, 35, 36

1. Which of the following best describes why extracellular polymeric substances are important?

A. They are chemicals produced as part of the immune response to microbial invasion.

B. They are components of a biofilm secreted by the host cells as an immune response to wall off the pathogens.

C. They are components of a biofilm secreted by the microbes present.

D. They are secreted by free-living bacteria as virulence factors to allow them to penetrate the bloodstream.

Difficulty: Moderate

ASM Standard: 20, 21, 22

1. Which of the following media is commonly used to determine the oxygen requirements of a bacterial species?

A. chocolate agar medium

B. Mueller-Hinton agar medium

C. thioglycolate medium

D. tryptic soy medium

Difficulty: Moderate

ASM Standard: 11, 35, 36

1. Which of the following best describes how a microaerophile would grow in a thioglycolate tube culture?

A. a short distance below the top of the medium, but not at the top

B. at the bottom of the medium only, with no growth in the middle or top

C. near and at the top of the medium, with no growth at the bottom

D. throughout the medium

Difficulty: Moderate

ASM Standard: 20, 22

1. Which of the following is not an example of an enzyme used to detoxify reactive oxygen species?

A. catalase

B. permeases

C. peroxidases

D. superoxide dismutases

Difficulty: Moderate

ASM Standard: 11, 20, 22

1. A candle jar is often used to grow which type of bacteria?

A. capnophiles

B. microaerophiles

C. obligate aerobes

D. obligate anaerobes

Difficulty: Moderate

ASM Standard: 14, 20, 22, 36

1. Which of the following is the most common category of bacteria?

A. acidophiles

B. alkaliphiles

C. extreme alkaliphiles

D. neutrophiles

Difficulty: Easy

ASM Standard: 13, 14, 20, 22, 36

1. Human pathogens are generally which type of microbe?

A. mesophiles

B. psychrophiles

C. psychrotrophs

D. thermophiles

Difficulty: Moderate

ASM Standard: 14, 20, 22, 26

1. Food spoilage is often caused by which type of microbe?

A. mesophiles

B. psychrophiles

C. psychrotrophs

D. thermophiles

Difficulty: Moderate

ASM Standard: 14, 20, 22, 36

1. Which type of microbes thrive in the Great Salt Lake?

A. barophilic

B. barotolerant

C. extreme halophiles

D. halotolerant

Difficulty: Easy

ASM Standard: 11, 20, 22

1. Which type of organism can survive at great depths in the ocean?

A. acidophilic

B. barophilic

C. barotolerant

D. halophilic

Difficulty: Moderate

ASM Standard: 11, 20, 22

1. Which range of the electromagnetic spectrum is considered photosynthetically active radiation?

A. from ultraviolet to near infrared

B. from visible light to near infrared

C. in near infrared only

D. in visible light only

Difficulty: Difficult

ASM Standard: 11, 20, 22

1. In batch culture, how does the log phase of the bacterial growth curve appear?

A. exponential on a semi-log scale

B. linear on a semi-log scale

C. logarithmic on an arithmetic scale

D. logarithmic on a semi-log scale

Difficulty: Difficult

ASM Standard: N/A

1. Which of the following best describes the enzymes of extreme alkaliphiles?

A. They have many acidic amino acids.

B. They have relatively high isoelectric points.

C. They have relatively high numbers of negatively charged surface amino acids.

D. They have the ability to pump protons out of cells.

Difficulty: Difficult

ASM Standard: 11, 20, 22

1. Capnophiles are bacteria that grow best under which of the following conditions?

A. relatively high CO₂ and relatively low oxygen concentrations

B. relatively high oxygen and relatively low CO₂ concentrations

C. relatively low CO₂ and oxygen concentrations

D. relatively low oxygen and CO₂ concentrations

Difficulty: Difficult

ASM Standard: 11, 20, 22

1. Which of the following best describes the cell membranes of microbes that thrive at low temperatures?

A. They have only one layer.

B. They have relatively even amounts of saturated and unsaturated fatty acids.

C. They have relatively high amounts of saturated fatty acids.

D. They have relatively high amounts of unsaturated fatty acids.

Difficulty: Difficult

ASM Standard: 11, 20, 22

1. If you grow two species of bacteria on mannitol salt agar to determine which can ferment mannitol, and you know both species can grow on the medium, which type of medium is the agar?

A. differential

B. selective

C. both a differential medium and a selective medium

D. neither a differential medium nor a selective medium

Difficulty: Difficult

ASM Standard: 20, 22, 33, 34

1. Which of the following pigments are especially useful at great depths, where less light penetrates?

A. bacteriorhodopsin and carotenoids

B. carotenoids and chlorophylls

C. fucoxanthin and carotenoids

D. fucoxanthin and phycobilins

Difficulty: Difficult

ASM Standard: 11, 20, 22

1. Which of the following microbes uses light energy to pump hydrogen and sodium?

A. Bacteriodetes

B. Campylobacter

C. Chlamydomonas

D. Halobacterium

Difficulty: Difficult

ASM Standard: 34

1. Which of the following is true of using a Petroff-Hausser chamber to do a direct cell count?

A. Identical squares, all the same size, are etched into the slide.

B. If the sample was diluted, then the concentration must be corrected accordingly.

C. It is not necessary to know the volume of the sample added to the slide.

D. The chamber does not resemble a hemocytometer.

Difficulty: Moderate

ASM Standard: 35, 36

1. Which of the following would be the best choice for distinguishing living and dead bacteria in a cell count?

A. using a Coulter counter or other electronic counting method

B. using a streak plate, spread plate, or pour plate

C. using gram staining or a similar method

D. primary and secondary fluorescent stains

Difficulty: Moderate

ASM Standard: 35, 36

1. What is the goal number of CFUs on a spread plate if a serial dilution is done correctly?

A. 1–10 per plate

B. 30–300 per plate

C. 400–900 per plate

D. 1000 or more per plate

Difficulty: Easy

ASM Standard: 35, 36

True/False

1. The largest component of the dry weight of a biofilm is usually extracellular polymeric substances.

Difficulty: Easy

ASM Standard: 21

1. Generation time in prokaryotes refers to the amount of time required for the doubling of the population through a single round of binary fission.

Difficulty: Easy

ASM Standard: N/A

1. Estimates of coliforms in water are often made using most probable number techniques.

Difficulty: Moderate

ASM Standard: 36

1. Quorum sensing always occurs between members of the same species.

Difficulty: Moderate

ASM Standard: 12

1. Halotolerant microbes cannot grow without high concentrations of salt.

Difficulty: Moderate

ASM Standard: 11, 13, 20, 22

1. Fungi can generally thrive in drier environments than can bacteria.

Difficulty: Moderate

ASM Standard: 11, 20, 22

1. MacConkey agar can be used to select for the growth of gram-positive bacteria, making it especially useful to study Enterobacteriaceae.

Difficulty: Difficult

ASM Standard: 11, 20, 22, 33, 34, 36

1. Some halotolerant microbes are important causes of food poisoning.

Difficulty: Difficult

ASM Standard: 11, 20, 22, 23

Matching

1. Match each type of organism with the best description of its oxygen requirements.

Answers: A. iv., B. v., C. iii., D. ii., E. i.

Difficulty: Easy

ASM Standard: 11, 20, 22

1. Match each type of microbe with the best example.

Answers: A. i., B. iv., C. iii., D. ii.

Difficulty: Difficult

ASM Standard: 11, 14, 20, 22

1. Match each type of microbe with the best description.

Answers: A. ii., B. iv., C. i., D. v., E. iii.

Difficulty: Moderate

ASM Standard: 11, 14, 20, 22

1. Match each type of medium with the best description.

Answers: A. iv., B. ii., C. v., D. i., E. iii.

Difficulty: Moderate

ASM Standard: 11, 20, 22, 33, 34

1. Match each microbe with the best description.

Answers: A. ii., B. i., C. iv., D. iii.

Difficulty: Difficult

ASM Standard: 11, 20, 22, 33, 34

Fill in the Blank

1. The process of division by which cells split from a parent filament is called ________.

Difficulty: Easy

ASM Standard: 22

1. The generation time for a particular bacterial species in a particular batch culture is called the ________.

Difficulty: Easy

ASM Standard: N/A

1. Turbidity is measured using a ________.

Difficulty: Easy

ASM Standard: 36

1. When a spread plate is used to estimate bacterial numbers, the numbers are reported as ________.

Difficulty: Moderate

ASM Standard: 36

1. ________ organisms do not require high salt concentrations for growth but can grow in salty environments.

Difficulty: Moderate

ASM Standard: 11, 20, 22

1. ________ is a measure of available moisture.

Difficulty: Moderate

ASM Standard: N/A

1. ________is when the cell membrane moves away from the cell wall due to osmosis occurring within the cytoplasm.

Difficulty: Moderate

ASM Standard: N/A

1. At low temperatures, membranes become ________ fluid unless they are able to modify their composition.

Difficulty: Moderate

ASM Standard: 11, 20, 22

1. The pigment used by Halobacteria to absorb light is called ________.

Difficulty: Moderate

ASM Standard: 11, 20, 22

1. The process of freeze-drying microbes so they can be stored until needed is called ________.

Difficulty: Difficult

ASM Standard: 36

1. ________ is an important accessory pigment used by brown algae to aid photosynthesis at low light levels.

Difficulty: Difficult

ASM Standard: 11, 20, 22

Short Answer

1. Which group of bacteria commonly divides using fragmentation?

Sample

Difficulty: Easy

ASM Standard: 11, 20, 22

1. Where are barophilic organisms found?

Sample

Difficulty: Easy

ASM Standard: 11, 20, 22

1. What happens during plasmolysis and what causes it?

Sample

Difficulty: Easy

ASM Standard: 11, 20, 22

1. What is the difference between the optimum oxygen concentration and the maximum permissive oxygen concentration?

Sample

Difficulty: Easy

ASM Standard: 11, 14, 20, 22

1. What is the following equation used for and what do the variables n, N_n, and N₀ refer to?

N_n = N₀2ⁿ

Sample

Difficulty: Moderate

ASM Standard: 35

1. Why do researchers often work with bacteria in the log phase of bacterial growth in a batch culture, rather than in other phases?

Sample

Difficulty: Moderate

ASM Standard: 11, 20, 22, 36

1. What are the most important signaling molecules for quorum sensing in gram-negative bacteria? How does this compare with the signaling molecules used by gram-positive bacteria?

Sample

Difficulty: Moderate

ASM Standard: 12

1. What is the standard way to grow obligate anaerobes in the laboratory?

Sample

Difficulty: Moderate

ASM Standard: 11, 20, 22, 36

1. Why is MacConkey agar considered both a selective and a differential medium?

Sample

Difficulty: Moderate

ASM Standard: 11, 34, 36

1. Why might you need to enrich media?

Sample

Difficulty: Moderate

ASM Standard: 11, 34, 36

1. Give an example of a halotolerant species that can cause food poisoning.

Sample

Difficulty: Difficult

ASM Standard: 11, 34

1. Mixed bacterial infections can occur that include both facultative anaerobes and obligate anaerobes. What happens when these species coexist?

Sample

Difficulty: Moderate

ASM Standard: 11, 14, 20, 22

1. Staphylococci thrive on human skin. What does this tell you about their environmental requirements?

Sample

Difficulty: Moderate

ASM Standard: 11, 20, 22, 23

1. Explain how you would do a serial dilution beginning with 1 mL of your bacterial culture.

Sample

Difficulty: Moderate

ASM Standard: 35, 36

1. Why are microbes in the stationary phase of growth less susceptible to antibiotics?

Sample

Difficulty: Difficult

ASM Standard: 7, 14

1. Which enzymes that detoxify reactive oxygen species are present or absent in obligate anaerobes and aerotolerant organisms?

Sample

Difficulty: Difficult

ASM Standard: 11, 14, 20, 22

1. Why is an enzyme from Thermus aquaticus especially useful for PCR?

Sample

Difficulty: Difficult

ASM Standard: 11, 20, 22, 26

Brief Essay

Essay Question Rubric

Assume rating/grading scale for the question ranges from 0 to 3 points.

1. Using the standard equation to calculate number of cells at each generation, how many cells would be present after four generations in a population undergoing exponential growth that started with a population of two cells? How does this compare with the size after four generations of a similar population that started with eight cells?

Sample

Difficulty: Moderate

ASM Standard: 35

1. Explain what factors influence the length of the lag phase in a batch culture, and why.

Sample

Difficulty: Moderate

ASM Standard: 36

1. Why is it helpful for some bacteria, such as Staphylococcus aureus, to produce virulence factors during the stationary phase of growth in a batch culture?

Sample

Difficulty: Difficult

ASM Standard: 13

1. There has been considerable concern about finding good ways to treat infections involving biofilms, such as those that develop on medical devices. What characteristics of biofilms complicate the treatment of infections involving biofilms?

Sample

Difficulty: Difficult

ASM Standard: 2, 14, 21

1. What are some ways in which the structures of thermophiles and hyperthermophiles differ in order to help them thrive at high temperatures?

Sample

Difficulty: Difficult

ASM Standard: 11, 14, 20, 22

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