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 microorganisms that exploit the same resources in a similar way.

Question 6

Why are soil particles not typically covered in a thick, slimy layer of microbial growth?

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 root with little penetration, while endomycorrhizae penetrate deeply into root tissue.

Question 9

A freshwater lake exhibits summer stratification. Which microbial processes would you expect to dominate in the hypolimnion (anoxic zone)?

Accepted Answer

Fermentation and anaerobic respiration

Question 10

In the mutualistic consortia 'Chlorochromatium aggregatum' found in stratified freshwater lakes, what is the primary ecological role of the green sulfur bacteria?

Accepted Answer

They are obligate anaerobic phototrophs that perform photosynthesis in anoxic, sulfidic environments.

Question 11

Which of the following best explains why levels of organic carbon and oxygen are inversely related in a river receiving sewage input?

Accepted Answer

Microbial degradation of organic carbon consumes oxygen, leading to decreased oxygen levels downstream from the input.

Question 12

Which of the following statements about biofilms is CORRECT?

Accepted Answer

Biofilms provide defense, allow cells to remain in favorable niches, and facilitate metabolic cooperation between species.

Question 13

Quorum sensing in bacteria involves which of the following mechanisms?

Accepted Answer

Accumulation of signaling molecules (such as AHL) that, at high concentrations, activate gene expression for group behaviors.

Question 14

Which of the following is a real-world consequence of biofilm formation?

Accepted Answer

Biofilms can cause pipeline congestion and corrosion in industrial settings.

Question 15

In the squid-Aliivibrio fischeri symbiosis, what is the role of quorum sensing?

Accepted Answer

It regulates the expression of bioluminescence genes in A. fischeri, allowing the squid to camouflage itself.

Question 16

Which of the following best describes a piezophile?

Accepted Answer

An organism that grows best under high hydrostatic pressure.

Question 17

Which metabolic process is most likely to occur near deep-sea hydrothermal vents?

Accepted Answer

Chemolithoautotrophy using reduced sulfur compounds as electron donors.

Question 18

A marine invertebrate, such as the Riftia giant tube worm, forms a mutualistic relationship with sulfide-reducing bacteria. What is the primary benefit to the worm?

Accepted Answer

The bacteria provide organic compounds synthesized from inorganic substrates, supporting the worm's nutrition.

Question 19

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

Accepted Answer

Unlimited access to all required nutrients and optimal environmental conditions.

Microbial Ecology: Diversity, Habitats, and Interactions

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