Question 1

Which of the following best describes the concept of functional redundancy in a microbial community?

Accepted Answer

Multiple microbial species can perform the same ecological function, so the loss of one species does not disrupt the process.

Question 2

A patient receives a fecal microbiota transplant (FMT) to treat a recurrent Clostridioides difficile infection. What is the primary ecological principle behind the effectiveness of this treatment?

Accepted Answer

Restoration of colonization resistance by reintroducing a diverse and balanced microbial community.

Question 3

Which process in the nitrogen cycle is responsible for converting nitrate ($$NO_3$$^-$$) back into atmospheric nitrogen gas (N_2$)?

NO_3$^- \rightarrow N_2$

Accepted Answer

Denitrification

Question 4

A microbial community in a freshwater lake is exposed to a pulse disturbance (e.g., a short-term pollutant spill). After the pollutant is removed, the community returns to its original composition. This property is best described as:

Accepted Answer

Resilience

Question 5

Which of the following is an example of mutualism in microbial ecology?

Accepted Answer

A lichen, where a fungus provides structure and an alga or cyanobacterium provides food through photosynthesis.

Question 6

Which adaptation allows acidophilic microbes to survive in environments with very low pH?

Accepted Answer

Pumping excess protons out of their cells to maintain a stable internal pH.

Question 7

In the sulfur cycle, which microbial process is responsible for the production of hydrogen sulfide ($$H_2S$$), often detected by its rotten egg smell?

$$SO_4$$^{2-} \rightarrow H_2S$$

Accepted Answer

Sulfate reduction

Question 8

A bacterium that can switch between aerobic respiration, nitrate respiration, and fermentation depending on environmental conditions is best described as a:

Accepted Answer

Generalist

Question 9

Which evolutionary mechanism most rapidly spreads antibiotic resistance genes between unrelated bacterial species in the human gut?

Accepted Answer

Horizontal gene transfer

Question 10

Which of the following best explains why a highly diverse gut microbiome reduces the risk of pathogen colonization?

Accepted Answer

Competitive exclusion, where healthy microbes outcompete pathogens for space and nutrients.

Question 11

Which microbial product is a short-chain fatty acid (SCFA) that directly fuels colon epithelial cells and helps maintain gut barrier integrity?

Accepted Answer

Butyrate

Question 12

A microbial biofilm forming on a medical implant becomes highly resistant to antibiotics compared to planktonic cells of the same species. This resistance is primarily due to:

Accepted Answer

Protective extracellular matrix and cooperative microbial interactions

Question 13

Which of the following scenarios represents amensalism?

Accepted Answer

A bacterium secretes antibiotics that inhibit nearby bacterial competitors.

Question 14

A microbial community in permafrost begins to metabolize newly thawed organic matter, releasing $$CO_2$$ and $$CH_4$$ into the atmosphere and accelerating global warming. This is an example of:

Accepted Answer

A positive climate feedback loop

Question 15

Which of the following best describes the role of microbes in the carbon cycle?

Accepted Answer

They fix atmospheric $$CO_2$$ into organic molecules and decompose organic matter, releasing $$CO_2$$ back into the atmosphere.

Question 16

Which adaptation allows deep-sea piezophilic microbes to survive under extreme pressure?

Accepted Answer

Adjusting cell membrane composition to maintain flexibility.

Question 17

A soil loses its ability to degrade cellulose after a fungal pathogen eliminates a single bacterial species responsible for this process. What does this observation suggest about the original community?

Accepted Answer

It had low functional redundancy.

Question 18

Which of the following is a real-life example of microbial succession?

Accepted Answer

After a forest fire, spore-forming bacteria colonize first, followed by nitrogen-fixing cyanobacteria, and later by diverse decomposers.

Question 19

Which of the following best describes the hygiene hypothesis in relation to the human microbiome?

Accepted Answer

Children exposed to a greater variety of microbes develop stronger immune systems.

Question 20

Which type of symbiotic relationship is illustrated by bacteriophages infecting and lysing bacteria?

Accepted Answer

Parasitism

Microbial Ecology: Community Dynamics, Interactions, and Human Health

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