Ch 31

Question 1

Ionized ammonia applied to soil is effectively retained because clays in the soil have a charge that is ____

A. positive.
B. negative.
C. uncharged.
D. none of these

Answer 1

negative

Question 2

An average gram of forest soil contains about

A. 2  109 bacteria and archaea.
B. 4  107 bacteria and archaea.
C. 4  107 protists.
D. 2  109 fungi.

Answer 2

4 x 10^7 bacteria and archaea.

Question 3

A unique feature of terrestrial filamentous fungi not found in aquatic fungi is

A. oxygen-impermeable structures including sclerotia and hyphal cords.
B. formation of flagellated spores that aid in spore dispersal.
C. mitochondria with highly invaginated cristae that permit more rapid diffusion of oxygen for oxidative phosphorylation.
D. all of the choices

Answer 3

oxygen-impermeable structures including sclerotia and hyphal cords

Question 4

Geosmin, which contributes to the characteristic earthy odor of soils, is produced primarily by the genus

A. Streptomyces.
B. Paramecium.
C. Caenorhabditis.
D. Armillaria.

Answer 4

Streptomyces

Question 5

One of the more important genera of gram-positive aerobic actinomycetes found in soils is

A. Streptomyces.
B. Bdellovibrio.
C. Acinetobacter.
D. Pseudomonas.

Answer 5

Streptomyces

Question 6

Most organic matter found in soils results from primary producers such as

A. cyanobacteria.
B. vascular plants.
C. photosynthetic protists.
D. none of the choices

Answer 6

Vascular plants

Question 7

Mycorrhizae are formed by the association of plants with

A. algae.
B. actinomycetes.
C. cyanobacteria.
D. fungi.

Answer 7

Fungi

Question 8

The ____________ mycorrhizae are the most common type of mycorrhizae.

A. arbuscular
B. ericaceous
C. orchidaceous
D. monotropoid

Answer 8

arbuscular

Question 9

In the process of forming a root nodule, species of Rhizobium differentiate to form a type of cell called a

A. lymph node.
B. bacteroid.
C. nucleoid.
D. vesicle.

Answer 9

bacteroid

Question 10

A major organism involved in associative nitrogen fixation in the rhizosphere of many plants is

A. Azospirillum.
B. Rhizobium.
C. Frankia.
D. Pseudomonas.

Answer 10

Azospirillum

Question 11

Ti plasmids in the species Agrobacterium tumefaciens

A. is required for nitrogen fixation.
B. causes the formation of tumors.
C. carries the genes needed for root nodule development.
D. carries the genes needed for formation of bacteroids.

Answer 11

causes the formation of tumors.

Question 12

In a mycorrhizal relationship, the fungal component can assist in providing phosphorus and water to the plant. The plant in turn provides the fungus with

A. metal cofactors.
B. organic carbon.
C. nitrogen.
D. carbon dioxide.

Answer 12

Organic carbon

Question 13

Actinorrhizae can benefit the plant by providing it with the products of

A. nitrification.
B. denitrification.
C. nitrogen fixation.
D. sulfate reduction.

Answer 13

nitrogen fixation

Question 14

Rhizobium and Bradyrhizobium are significant contributors to which process when engaged in a symbiotic relationship with leguminous plants?

A. nitrification
B. nitrogen fixation
C. denitrification
D. sulfate reduction

Answer 14

nitrogen fixation

Question 15

A common resident of the rhizosphere that can enhance plant growth is

A. Arthrobacter.
B. Erwinia.
C. Sphingomonas.
D. Pseudomonas.

Answer 15

Pseudomonas

Question 16

The formation of an infection thread is an important initial part of microbial interactions with plants in the process of

A. nitrification.
B. nitrogen fixation.
C. denitrification.
D. sulfate reduction.

Answer 16

nitrogen fixation

Question 17

When rhizobia approach a plant root, the plant initially responds by
A. an oxidative burst.
B. an increase in exudate.
C. releasing flavonoid inducer molecules.
D. producing leghemoglobin.

Answer 17

an oxidative burst

Question 18

The region of soil in the immediate vicinity of the roots of plants is called

A. plant crust.
B. rhizosphere.
C. phyllosphere.
D. microbivory.

Answer 18

rhizosphere

Question 19

Which of the following statements is correct?

A. All plants maintain a mycorrhizal relationship.
B. Most plants maintain a mycorrhizal relationship.
C. Some plants maintain a mycorrhizal relationship.
D. Only a few plants maintain a mycorrhizal relationship.

Answer 19

Most plants maintain a mycorrhizal relationship.

Question 20

One of the most common bacterial genera cultured from plant leaves is

A. Nocardia.
B. Cellulomonas.
C. Sphingomonas.
D. Arthrobacter.

Answer 20

Sphingomonas

Question 21

The stems and leaves of plants, called the ___________, provide a habitat for a wide variety of microorganisms.

A. plant crust
B. rhizosphere
C. phyllosphere
D. microbivory

Answer 21

phyllosphere

Question 22

Recent studies indicate that active prokaryotic assemblages are present in high-temperature oil reservoirs, including such genera as

A. Thermotoga
B. Thermoanaerobacter
C. Agrobacterium
D. only Thermotoga and Thermoanaerobacter

Answer 22

only Thermotoga and Thermoanaerobacter

Question 23

48. Microbial processes take place in
    A. shallow subsurface where water flowing from the surface moves below the plant root zone.
    B. regions where organic matter, originating from the Earth’s surface in times past, has been transformed by chemical and biological processes to yield coal.
    C. zones where methane is being synthesized as a result of microbial activity.
    D. all of the choices

Answer 23

D. all of the above

Question 24

A large reserve of methane is found in a pocket below the ocean floor and isotope analysis revealed that the 13C/12C ratio is lower than that predicted by the natural occurrence of these isotopes. This finding suggests that the methane was produced by

A. a geochemical process.
B. the metabolic activity of microorganisms.
C. a radioactive decay process.
D. oxidation of sulfite.

Answer 24

the metabolic activity of microorganisms.