Review Questions

Short Answer

1. Describe why a microbial mat has green, pink, and black layers.

2. Why do lakes in temperate regions stratify during the summer months?

3. Why is there a high concentration of microbes in the rhizosphere?

4. What dictates whether a form of an element is suitable for use as an energy source versus a terminal electron acceptor?

5. Why does wood resting at the bottom of a bog resist decay?

6. What is the importance of nitrogen fixation?

7. Describe the relationship between ammonia oxidizers and nitrite oxidizers.

8. How do hydrothermal vents support a thriving community of microbes, clams, and tubeworms?

9. Give examples of free-living and symbiotic nitrogen-fixing microorganisms. Are these prokaryotic or eukaryotic?

10. Describe the steps that lead to the formation of the symbiotic relationship between rhizobia and leguminous plants.

Multiple Choice

1. Cyanobacteria are A. primary producers. D. decomposers.

B. consumers. C. herbivores. E. more than one of the above.

2. Which of the following is false?

A. Culture techniques provide an accurate way of determining the predominant members of a microbial community such as a biofilm.

B. Fluorescence in situ hybridization (FISH) can be used to distinguish subsets of prokaryotes based on their 16S rRNA sequences.

C. Polymerase chain reaction (PCR) can be used to distinguish subsets of prokaryotes based on their 16S rRNA sequences.

D. Denaturing gradient gel electrophoresis (DGGE) can be used to separate PCR products.

E. Studying the genome of one organism can give insights into the characteristics of another.

3. The decomposition of organic matter

A. is carried out by only a few bacterial species.

B. produces oxygen.

C. involves all the biogeochemical cycles discussed.

D. involves primarily photosynthesis.

E. is largely symbiotic.

4. Which of the following pairs that relate to aquatic environments does not match?

A. Oligotrophic—nutrient poor

B. Hypoxic—oxygen poor

C. Hypolimnion—lower layer

D. Epilimnion—oxygen poor

E. Eutrophic—nutrient rich

5. Which of the following pairs that relate to terrestrial environments does not match?

A. R horizon—topsoil

B. Bacillus—endospores

C. Streptomyces—geosmin production

D. Fungi—lignin degradation

E. Rhizosphere—soil that adheres to plant root

6. Atmospheric nitrogen can be used

A. directly by all living organisms.

B. only by aerobic bacteria.

C. only by anaerobic bacteria.

D. in symbiotic relationships between rhizobia and plants.

E. in photosynthesis.

7. Which process converts ammonium (NH4+) into nitrate

A. Nitrogen fixation B. Ammonification C. Nitrification D. Denitrification E. Anammox

8. Energy for ecosystems can come from

A. sunlight via photosynthesis.

B. oxidation of reduced inorganic chemicals by chemoautotrophs.

9. Mycorrhizae represent associations between plant roots and microorganisms that

A. are antagonistic.

B. help plants take up phosphorus and other nutrients from soil.

C. involve algae in the association with plant roots.

D. form nodules on the plant's leaves.

E. lead to the production of antibiotics.

10. In symbiotic nitrogen fixation by rhizobia and legumes

A. the amount of nitrogen fixed is much greater than by nonsymbiotic organisms.

B. neither the bacteria nor the legume can exist independently.

C. the bacteria enter the leaves of the legume.

D. the bacteria operate independently of the legume.

784 Chapter 30 Microbial Ecology Applications

1. A farmer who was growing soybeans, a type of legume, saw an Internet site advertising an agricultural product for safely killing soil bacteria. The ad claimed that soil bacteria were responsible for most crop losses. The farmer called the agricultural extension office at a local university for advice. Explain what the extension office crop adviser most likely told the farmer about the usefulness of the product.

2. Recent reports suggest that human activities, such as the generous use of nitrogen fertilizers, have doubled the rate at which elemental nitrogen is fixed, raising concerns of environmental overload of nitrogen. What problems could arise from too much fixed nitrogen, and what could be done about this situation?

Critical Thinking

1. Each colony of microorganisms growing on an agar plate arises from a single cell (see photo). Colonies growing close together are much smaller than those that are well separated. Why would this be so?

2. An entrepreneur found an economically feasible way of collecting large amounts of sulfur from underwater hot vents in the Pacific Ocean. The sulfur will be harvested from the microorganisms found in the vent areas. A group of ecologists argued that the project would destroy the fragile ecosystem by depleting it of usable sulfur. The entrepreneur argued that the environment would not be harmed because the vents produce an unlimited source of sulfur for the clams and tube worms in the area. Explain who is correct in their assessment.

Nester-Anderson-Roberts: I V. Applied Microbiology I 31. Environmental I I © The McGraw-Hill

Microbiology, A Human Microbiology: Treatment of Companies, 2003 Perspective, Fourth Edition Water, Wastes and

Polluted Habitats

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  • p
    Why Does Wood Resting at the bottom of a bog resist decay and answer?
    3 years ago
  • Celendine
    Why does wood resistant at bottom of a bog resist decay?
    3 years ago

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