Question 1

Which of the following best describes the difference between species richness and species abundance in microbial ecology?

Accepted Answer

Species richness refers to the number of different species present, while species abundance refers to the number of individuals of each species.

Question 2

Fluorescent in situ Hybridization (FISH) is a powerful tool in microbial ecology. Which of the following statements about FISH is CORRECT?

Accepted Answer

FISH uses fluorescing oligonucleotides that hybridize to rRNA sequences, allowing for the identification of specific microbial groups.

Question 3

Consider the following reactions catalyzed by nitrifying bacteria:

$$\mathrm{NH_3$ + \frac{3}{2}O_2$ \rightarrow NO_2$^- + H_2O}$$
$$\mathrm{NO_2$^- + \frac{1}{2}O_2$ \rightarrow NO_3$^-}$$

Which pair of genera is responsible for these reactions in the nitrogen cycle?

Accepted Answer

Nitrosococcus and Nitrobacter

Question 4

What is the main advantage of using MAR-FISH (Microautoradiography combined with FISH) in microbial ecology studies?

Accepted Answer

It allows researchers to determine both the identity of microorganisms and their ability to utilize specific substrates.

Question 5

Which of the following best defines a microbial guild?

Accepted Answer

A group of metabolically related organisms that exploit the same resources in a similar way.

Question 6

Why isn’t every soil particle completely covered in microbial growth, forming a slimy layer?

Accepted Answer

Because resources and growth conditions are often suboptimal, nutrients are not uniformly distributed, and competition exists among microbes.

Question 7

Which of the following statements about mycorrhizae is TRUE?

Accepted Answer

Mycorrhizae are mutualistic associations where fungi transfer inorganic nutrients to plants and receive carbohydrates in return.

Question 8

Which of the following best describes the difference between ectomycorrhizae and endomycorrhizae?

Accepted Answer

Ectomycorrhizae form a sheath around the outside of roots with little penetration, while endomycorrhizae penetrate deeply into root tissue.

Question 9

In a stratified freshwater lake during summer, which microbial processes dominate in the hypolimnion (anoxic zone)?

Accepted Answer

Fermentation and anaerobic respiration

Question 10

Which of the following is a correct statement about the mutualistic relationship between the Hawaiian bobtail squid and Aliivibrio fischeri?

Accepted Answer

The squid provides nutrients to A. fischeri, which in turn produces bioluminescence that helps camouflage the squid from predators.

Question 11

Which of the following best explains why biofilms are important in both medical and industrial contexts?

Accepted Answer

Biofilms protect microbes from environmental threats and can cause persistent infections or clog pipelines.

Question 12

Which of the following is a key feature of quorum sensing in bacteria?

Accepted Answer

It allows bacteria to coordinate gene expression based on cell density using signaling molecules such as acylated homoserine lactone (AHL).

Question 13

Which of the following best describes the role of chemolithotrophic bacteria near deep-sea hydrothermal vents?

Accepted Answer

They use inorganic compounds such as $$\mathrm{H_2S} or$$ $$\mathrm{Fe$$^{2+}$$} as $$electron donors to support primary production in the absence of sunlight.

Question 14

Which of the following is a correct example of a mutualistic relationship found at hydrothermal vents?

Accepted Answer

Riftia giant tube worms and sulfide-reducing bacteria

Question 15

Which of the following resources or conditions is NOT typically a limiting factor for microbial growth in nature?

Accepted Answer

Unlimited supply of organic carbon

Question 16

A researcher wants to measure microbial diversity in a soil sample. Which molecular approach would be most appropriate?

Accepted Answer

Amplifying and sequencing 16S rRNA genes from community DNA

Question 17

Which of the following statements about the distribution of Archaea and Bacteria in the ocean is correct?

Accepted Answer

Bacteria dominate surface waters, while Archaea become more abundant in deeper, nutrient-poor waters.

Question 18

Which of the following best describes a piezophile?

Accepted Answer

An organism that grows best under high hydrostatic pressure, such as those found in deep-sea environments.

Question 19

Which process is primarily responsible for the inverse relationship between organic carbon and oxygen levels in a river receiving sewage input?

Accepted Answer

Microbial respiration consumes oxygen as organic carbon is degraded.

Microbial Ecology: Diversity, Interactions, and Environments

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